I can't post photos today for some reason, but I have been examining my 1927A1 after some extensive shooting. I installed a new barrel, standard link and bushing during the rebuild. I am not sure who made the barrel as it isn't marked and it was still in the wax paper overwrap when given to me, but it was practically a drop in. To that end, I wanted to ask you gentlemen a few questions about barrel and lug fitting.
The barrel and bushing are both new and fit very well into the slide, but everything is more of a 'mil-spec' fit & finish configuration than match grade in nature. The firing pin strike is dead center and the headspace is within the mil-specification. The gun doesn't mark up/chew up the brass either. In fact, spent cases hardly look as if they have been through a gun.
What I am noticing, however, is the rear 1/3 of each lug in the slide is polishing the Parkerizing away. The hood is .006" from the breechface when in battery and left side of the chamber edge (looking down the sight plane) is making solid contact with the slide extension.
I'm not seeing any 'edge' on the lugs or any rolling or peening, but they are polished. The lower lug areas are smooth and barely marking the Parkerized finish. The finish also hasn't been pounded off the recoil spring guide yet.
I am planning on a Kart or Wilson semi drop-in barrel in the near future, but in the interim, what is your general opinion on this? Which barrel is less labor intensive to install?
Here is something I discovered...
If I unload the gun (fully assembled with recoil spring) and point the muzzle up, the barrel drops down before the slide moves back.
If I point the muzzle down and slowly return the slide to battery, I can feel a slight drag where the top/front of the chamber is just dragging along the rear edge of the rear-most lug as it goes into battery.
I've never looked this closely at this aspect of this gun before, so for reference, I tore down one of our .38 Super Government Models and it behaved in the same fashion.
If I pull my slide back just a fraction, not far enough for the barrel to link down, and hold the muzzle at the floor, I can push the barrel back towards the breechface probably anout .040" or so by eye. If I hold the muzzle up, the chamber stays away from contacting the rear edge of the rear lug and the barrel links down smartly before the slide can contact any part of the chamber.
Is the barrel driven forward under recoil? Based on the polished mark that the chamber has made against the rearmost surface of the rearmost slide lug, it would appear that the barrel is moving forward against the slide.
As a side note, the primer strikes are dead-center and the gun leaves almost no marks on fired brass.
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Is the barrel driven forward under recoil?
Yes.
When the gun's in battery before firing, the recoil spring pushes the slide fully forward against the barrel (barrel hood with a fitted barrel, chamber face with others). So, the barrel is as far back in the slide as it can possibly be.
When fired and before the onset of linkdown, friction between the bullet and barrel pulls the barrel forward in the slide and the case pushes the slide aftward, so the barrel is now as far forward in the slide as it can possibly be. While all this is going on, the barrel is still engaged with and locked to the slide and both are moving aftward with respect to the frame.
In the average Gov't Model 1911, the barrel has a bit less than 0.013" of horizontal play when it's all the way up in the slide.
Does my description sound like a normal, mil-spec clearanced pistol?
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Does my description sound like a normal, mil-spec clearanced pistol?
The only thing that seems amiss is the 0.040" of horizontal barrel movement in the slide. The maximum for a Gov't Model with the tolerances stacked for the most play is 0.020".
Even though the 0.040" you mentioned is an eyeball estimate, it might not hurt to see if the headspace exceeds the max of 0.920".
My eyeball is always generous to be certain... I will measure it to be sure.
One way to get a fairly accurate measure of dynamic (barrel fully forward in slide) headspace is add measurements of:
* Barrel hood-to-chamber stop shoulder distance and
* Hood-to-breechface gap when barrel's fully forward in the slide.
The sum should be no greater than 0.920"
I just fitted a Kart EZ fit barrel in my s/s Taurus in 2hrs, using their install kit. I am a rookie at this and I was going very slowly. I followed their instructions which I thought were generally clear. Their bushing went in to my slide perfectly. I have .002 hood/breechface clearance (I removed ~.015 from the hood), sliding contact between the slide stop and both lower barrel legs and contact with both "fitting pads" in the rear lug (I filed them about half off during the fitting). I called Kart to ask if I was done and they said yes. I fired 30 rounds to see if any parts were battering each other and everything went well - no malfs - and improved accuracy. I will have access to a ransom rest next week to really get a good accuracy read. The lock up is incredibly tight. I tried your up and down tests and couldn't move anything. I'm a happy camper.
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I will have access to a ransom rest next week to really get a good accuracy
read.
Hope you're planning on getting accuracy reads with the gun in both the original and fitted-barrel configurations. And in the excitement, don't forget about the warmup shots for each barrel.
The barrel bed and lower lugs look perfect; smooth and flat. There are two shiny marks on the slide stop pin on either side of the area where the link rides, but no peening, but I am concerned about the slide lugs...
When I look into my upside down slide (bare) I see a shiny pattern along the rear edge of the slide lugs from where the barrel is making contact with it. There definitely appears to be a slight 'step' in this polished location, although it has been there since I acquired the weapon. There is no sharp or ragged edge that I can feel on either barrel or slide.
This is a mil-spec barrel that was still in wax paper when I acquired it, possibly a Swenson?
If I drop the barrel into the bare slide and push the barrel all the way back until the chamber extension makes contact with the slide, I can just get a .005" feeler gauge in between the breechface and the hood. That's within the Mil-Specs for the gun IIRC.
If I pull the barrel all the way forward into the slide lugs, I can get a .025" feeler gauge (tight) between the hood extension and the breechface. Again, not too bad for a mil-spec duty weapon, but it could, of course be better.
With recoil spring removed, the gun will fall in and out of battery under the slide's own weight and feels very smooth with none of the binding encountered with too long of a link.
With the gun fully assembled, If I gradually increase the thickness of the feeler guages, a .009" starts to push the slide rearward ever so slightly and it will go all the way to a .024"/.025" before the barrel 'just starts' to link down.
I plan on installing an Ed Brown Drop-In Barrel/Link/Bushing in the near future. My concern is, based on these descriptors, would I be doing any damage if I keep shooting the gun until then????
Log Man was kind enough to help me with understanding the dynamics of what is taking place in my gun. The chamber face is contacting the slide guide blocks because of the short hood and the polishing I see on the rear face of the slide lugs is from the barrel moving forward when firing and rapidly taking up that clearance. I don't know why this was so hard for me to envision. Must be the rocks in my head...
I am going to put a different barrel into this gun for sure. However, I am no expert on barrel and/or link fitting. I have been told that some of the 'drop- in' barrels have too short of a hood right out of the box, so I want to do it right. I neither want or need a 'match grade' weapon as this is a duty handgun, so please keep this fact in mind.
Since I carry this gun and it will see rain, I want a stainless barrel. I would like to find one with lower lugs finished, link and pin installed, but one that has a long enough hood that I could close up this gap.
I have been looking at the Ed Brown barrel, but would appreciate any input from those more experienced with barrel fitting than me.
IMHO, finding a drop-in barrel with a hood juuuust long enough to fill the hood-breechface gap on a particular slide would require the purchase of hundreds of barrels with the hope that one of them got made just for your slide - by accident!
As long as the dynamic headspace is within limits, and this is a carry gun (I think) I'd just look at the hood-breechface gap as a skinny loaded chamber inspection port/slot.
It is indeed a carry gun, but the rear edge of the lugs are getting hit pretty hard. When I go to the range, it is not uncommon for me to fire 500 to 1000 rounds in a single training session, so I think I can improve the gun's longevity by fitting a barrel with a longer hood.
I understand what you are saying. I'm looking for a decent semi-finished barrel that would allow me to close up the hood to breechface clearance.
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...the rear edge of the lugs are getting hit pretty hard.
Now I understand. Closing the gap (or even just reducing it significantly) will reduce the distance the slide moves aftward around the barrel when fired.
Guess I didn't have my thinking cap on!
If a Kart EZ-Fit comes with a long hood that requires fitting one of those might be what you need. If not, I think your only choice is a barrel with oversized hood and lugs - needing lots of fitting.
Yep, I was having a hard time envisioning the separate movements of the barrel and slide. I am looking at the Kart EZF as they do say the hood needs to be trimmed to fit. What is a proper method for removing material from the hood and keeping it square?
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What is a proper method for removing material from the hood and keeping it
square?
Not sure what's really proper, but I'd remove most of the material with a file and finish off the last thousandth or so with a stone.
To keep it square, clamp the barrel cross-wise in a good square drill press vise or machinist's vise with the hood protruding just a tad less than what needs to be removed. The side of the vise then acts as a "depth stop" to prevent filing/stoning off too much and also keeps the file/stone square to the chamber.
The critical part of hood fitting is getting the measurements so you know how much needs to be taken off the hood's length. Folks that fit lots of barrels may be able to tell how much just by eyeball and may even be able to tell from that about how many file strokes it'll take. I'm not one of those folks.
There's a good article in our Stickies (or maybe Tech Issues) by 1911 Tuner that covers barrel fitting.
My first impulse was to go genuine Colt, but judging from the new, unissiued Series 80's we have in the armory, all have about .022" to .024" hood clearance, so I assumed that a new Colt barrel would likely give me what I have right now.
I have narrowed it down to (2) Stainless Steel options; Storm Lakes Pre-Fit Barrel/Link/bushing and Ed Brown's Pre-Fit Link/Barrel Bushing. Any preference or experience with either one?
Headspacing question: I asuume they headspec these when they build them? So, if you do not have to trim the hood, headspacing would not change?
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Headspacing question: I asuume they headspec these when they build
them?
The barrels are just chambered reamed to a depth that will provide proper headspace (it has a 0.032" range) in most slides. The barrel, all by itself, has no headspace. How much headspace you end up with depends on how the barrel fits into the slide and how the slide is made.
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So, if you do not have to trim the hood, headspacing would not change?
Because there is no actual headspace (distance from chamber stop shoulder to breechface) until the barrel's in the slide, there's no pre-existing headspace in the barrel to get changed. All the barrel has is its distance from the chamber stop shoulder to the end of the hood. If the barrel just happens to fit into the slide without the hood needing a trim, the headspace created when the barrel's installed is just the barrel's stop shoulder-to-hood distance plus the gap (if any) between the hood and breechface when the barrel is fully forward in the slide.
Ok... That's starting to make more sense to me now. Working with Mil-Spec duty guns, I have never really encountered anything like this.
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It is indeed a carry gun, but the rear edge of the lugs are getting hit
pretty hard. When I go to the range, it is not uncommon for me to fire 500 to
1000 rounds in a single training session, so I think I can improve the gun's
longevity by fitting a barrel with a longer hood.
Please correct me on something. You are assuming that you have two choices: either the barrel hood contacts the breech, and all is well, giving you longevity. Or else it will contact and batter the barrel chamber? I don't think either of these statements is true. Your barrel chamber sides may be hitting the slide, but the barrel is supposed to be relieved slightly to prevent it, in my understanding.
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Your barrel chamber sides may be hitting the slide, but the barrel is
supposed to be relieved slightly to prevent it, in my understanding.
Don't forget that an in-spec GI 1911's barrel gets driven into battery and held there by contact between the breech face guide blocks and the chamber face. The hood never, ever, touches the breechface. The gap works out to 0.006 +/- 0.004 inch.
[Edited: However, for slides and barrels made to older 1940's Ordnance specs, hood-breechface contact can sometimes occur as the gap works out to about 0.002 +/- 0.004 inch]
Because of this, relieving the chamber face to avoid that contact would necessitate removing enough material so the hood contacts the breechface. Form what the OP's said, the hood-breechface gaps are about 0.022 to 0.024 inch. Removing that much from the chamber face will reduce the static (gun in battery) headspace by that amount (perhaps putting it out of spec) and also increase the fore-aft play of the barrel in the slide by that amount. The later will also increase the battering between the slide and barrel locking lugs - which the OP was concerned about.
I think trimming the chamber face merely to obtain hood-breechface contact is unwise. If the OP wants his gun(s) to have hood-breechface contact, he needs to fit a barrel with a too-long hood.
But, IMHO, hood-breechface contact is one of those things that's desireable only in a ultra-tight, fitted barrel, Bullseye competition range gun that spends most of its pampered life in a closed gun box.
I think all the OP really needs is a barrel that provides less fore-aft play in the slide. Not necessarily zero play.
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The hood never, ever, touches the breechface.
Well... That hasn't been my experience. I've seen a few that did operate in that condition... but most started the barrel's return to battery via breechface to hood contact, and the breechface never hit the barrel face. A truly in-spec barrel face is angled by about 1.5 degrees, +/- a couple minutes. That creates a small gap when the barrel is full in battery.
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Well... That hasn't been my experience. I've seen a few that did operate in
that condition... but most started the barrel's return to battery via
breechface to hood contact, and the breechface never hit the barrel face.
That 0.006 +/- 0.004 inch hood-breechface gap is based on the latest Ordnance blueprints.
But, using earlier (1943 & 1944) blueprints, the gap spec works out to about 0.002 +/- 0.004 inch, so for parts made to those older specs the barrel could sometimes be driven into battery by hood-breechface contact.
So I'll amend the statement in my previous post.
FWIW, the "nominal" hood-breechface gaps work out to 0.010" with the latest specs and 0.0055 inch using the older specs.
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A truly in-spec barrel face is angled by about 1.5 degrees, +/- a couple
minutes. That creates a small gap when the barrel is full in battery.
Hmm-m-m. That must be some sort of special kind of specification as it's not on any blueprint I've got - new or old.
My point is this:
I shoot this gun a lot and I carry it too. Currently, the barrel hood is about .024" from the breechface and by closing that up, I can reduce a lot of barrel/slide impact. This is what I am trying to accomplish. I don't think I need .004" hood/breechface clearance, but I would like less than the .024" I have currently. During my last range session, the pistol was so hot I couldn't hold onto it anymore. When I say I shoot a lot, I mean it.
Additionally, if I understand what Log Man and I were discussing, when the barrel is placed in the bare slide, the hood will contact the breechface and there will be some slight clearance between the rearmost barrel lug and rearmost slide lug.
I ordered an Ed Brown Semi-Drop In Barrel to fit to this pistol. What is a good distance to shoot for in a carry/duty pistol?
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"I think all the OP really needs is a barrel that provides less fore-aft
play in the slide. Not necessarily zero play..."
Exactly... What should I be shooting for on my duty pistol?
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Hmm-m-m. That must be some sort of special kind of specification as it's
not on any blueprint I've got - new or old.
Keep lookin'. There may be a specification in JK-2. If I can find the flippin' thing, I'll see if it's there.
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Exactly... What should I be shooting for on my duty pistol?
Probably a fore-aft play of barrel in slide of no more than the average Gov't Model play of about 0.012".
But be sure not to confuse fore-aft play with the gap between the hood and breechface. The two are only indirectly related.
F'rinstance, it's theoretically possible to have zero fore-aft play and a constant big gap between the hood and breechface. In this case, there's no gap between the breechface guide blocks and the chamber face.
It's also possible to have hood-breechface contact all the way into battery, but a gap when the gun's fired and the slide moves aftward over the barrel.
As an example, my target 1911:
* with its not-too-well fitted NM barrel; has its hood against the breechface in battery and a 0.004" gap coming out of battery - 0.004" of play.
* with its original GI barrel; has a hood-breechface gap of 0.011" in battery and a 0.013" gap coming out of battery - 0.002" of play.
According to the Ed Brown website, "All barrels are cut to drop in tolerances..". So I suspect you'll still have a hood-breechface gap with that barrel. You'll have to install the barrel to see how much fore-aft play you end up with. And with a standard length hood, there's nothing you can do to reduce the play of that barrel in that slide - unless you have the hood welded up and fitted.
Can't find it in JK-2. It may have been in one of Uncle Sugar's old drawings... but I've see it somewhere... or I've got it here somewhere. I'll keep lookin'.
Meanwhile... think about it like this, Dan...
When the barrel tilt up into full battery... if clearance isn't provided between breechface and barrel face... the barrel face gets deformed, and the bottom takes the greatest hit... which would tend to flatten the leading edge of the barrel's ramp... which isn't conducive to smooth feeding. The tilted angle in battery depends on how much the barrel tilts. Some don't require as much of an angled barrel face, while others require more.
I've taken a few old GI pistols apart that didn't have sufficient clearance, and found not only that the bottom of the ramp's edge was flattened... but also a mark in the left side of the chamber entrance where the extractor nose had beaten it.
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There may be a specification in JK-2.
Could you be thinking of the chamber face angling in JK-1, page 53, mentioned as a cure for chamber face battering?
That may be it... but I've seen it in Marine Corps shop drawings. For tightly fitted barrels, that angle is important. If the barrel is actually forced forward by the breechface bearing on the barrel face, the barrel takes a hit every time it goes to battery. If it's loosely fitted... it doesn't matter as much because of the forced gap between the two when the gun fires. If the hood is so short that the slide times the barrel into the slide via the barrel face alone... it sill takes a hit, just not as bad and the deformation will be slower in coming.
More often than not, if an ordnance barrel... read that as "Drop-In"... doesn't provide the 32nd inch gap with the frame... it should be filed to a slight angle and the barrel ramp recut/reshaped. I've found that it isn't usually necessary to angle the whole face up to the hood junction. Angling the ramp area is usually sufficient.
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But, IMHO, hood-breechface contact is one of those things that's desireable
only in a ultra-tight, fitted barrel, Bullseye competition range gun that
spends most of its pampered life in a closed gun box.
Thanks, that was my understanding as well. What has me puzzled is the fuss that is made about hood-breechface contact being necessary and desirable in all cases. And as Dan points out, H-B contact was absolutely not necessary for reliability. One more thought. Let's say you are going to consider more significant stuff, like a fit that includes more than one lug in contact with the slide. To get this type of fit, you will usually be removing metal from lugs 1 and 2 which will move the barrel forward and open up the H-B dimension a little. Wouldn't it be better to concentrate on an excellent 2 or 3 lug fit, instead of worrying about whether the hood rubs the breech?
Dan is correct on the point with hood to breechface contact. It's not a reliability tweak. It's primarily for accuracy, and secondarily for longevity/durability. It forces the barrel fully forward so that the lug... or ideally, the lugs... are in contact with the slide's lug (s) which eliminates the slide's "running" start... reducing lug battering.
The gun is actually a bit more reliable with a little hood to beechface clearance. Even when I fit a barrel closely...I first fit for none... and then cut .003 off the hood to provide a little. Like the late Bob Rodgers... I haven't been able to see any practical difference in the accuracy. Someone who is chasing half-inch groups at 50 yards may see it from a rest. Firing offhand, a shooter would have to be very good to be able to see it.
As far as the longevity/durability question goes, .003 inch of endshake won't make enough of a difference to be concerned over. The rifling will be worn smooth long before the lugs deform enough to create headspace issues.
I do NOT like to see the barrel pressed firmly forward via breechface to barrel face contact, though... and I'll create clearance at that point whenever I find it.
What controls the desireable 3/32" gap between chamber and ramp?
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I do NOT like to see the barrel pressed firmly forward via breechface to
barrel face contact, though... and I'll create clearance at that point whenever
I find it.
Now I'm getting confused - again.
When the slide returns to battery, there's only two places it can contact the barrel and move it forward out of linkdown: the hood and/or the chamber face.
If it's only the slide's breechface guide blocks (BFGB's, aka ledges) that drive the barrel into battery (by contact with the chamber face) then there must be at least some small gap between the hood and breechface. To eliminate that contact, enough material must be removed from the chamber face to transfer the driving force from it to the hood.
Then to create the 0.003" hood-breechface gap you mentioned, material must be removed from the hood but this will transfer the driving force back to the chamber face. Uh-oh, now there's chamber face contact. Gotta get rid of that. Uh-oh, now my gap at the hood is gone. Gotta...
Sounds kinda like a Catch-22 situation. What am I missing?
After another cup of coffee, the little light came on.
You dress down just the lower part of the chamber face to eliminate any contact there (and possible peening) leaving the contact between the upper part of the chamber face and the BFGB's/breechface ledges. And that contact make the 0.003" gap at the hood possible.
Just like you said back in Post #30? [should have signed up for remedial reading!]
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What controls the desireable 3/32" gap between chamber and ramp?
It's actually 1/32" and it's controlled by more than a dozen different frame, slide stop pin and barrel dimensions.
But to obtain the 1/32", if you don't have it, I just whittle on the barrel ramp with a good knife or scraper (keeping it straight) - without moving the top corner forward.
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Dan is correct on the point with hood to breechface contact. It's not a
reliability tweak. It's primarily for accuracy, and secondarily for
longevity/durability. It forces the barrel fully forward so that the lug... or
ideally, the lugs... are in contact with the slide's lug (s) which eliminates
the slide's "running" start... reducing lug battering.
The gun is actually a bit more reliable with a little hood to beechface clearance. Even when I fit a barrel closely...I first fit for none...and then cut .003 off the hood to provide a little. Like the late Bob Rodgers...I haven't been able to see any practical difference in the accuracy. Someone who is chasing half-inch groups at 50 yards may see it from a rest. Firing offhand, a shooter would have to be very good to be able to see it.
As far as the longevity/durability question goes, .003 inch of endshake won't make enough of a difference to be concerned over. The rifling will be worn smooth long before the lugs deform enough to create headspace issues.
I do NOT like to see the barrel pressed firmly forward via breechface to barrel face contact, though...and I'll create clearance at that point whenever I find it.
Thanks, Tuner. I'm always amazed at how many variables are in play when fitting a barrel. I'll keep in mind the possibility of lug deformation due to too much fore and aft movement. Before this I focused primarily on getting the support triangle of upper lugs and barrel feet to be correct and did not bother much with achieving breechface to hood contact.
My rear lug has some wear, but all of it is very smooth, from 82 years of use. In my gun, a slightly longer hood would reduce a lot of the 'float' that I have, even though my 1927A1 works all the time, everytime.
As I understand, the correct headspace has a .032" acceptable range. My current barrel has .024" between breechface and hood and my guide blocks are driving the barrel forward into battery. I would like to close this distance up a bit.
What affects the 3/32" gap between ramp and chamber throat?
Robert... The acceptable headspace range is .022 inch. .898-.920
The hood has nothing to do with headspace. Your barrel is being pushed into battery via breechface/barrel face contact when empty... but it may not be when a cartridge is present. Drop a brass case or loaded round into the chamber and see if it sits above the face of the hood. If it does... The barrel is being pushed forward by the slide via the case rim.
If this is what is happening... part of the .024 inch endshake is being closed up by the cartridge.
All I was ever instructed about headspace was to be sure a cartridge case was below the hood when dropped in the barrel. I worked on a Colt 1911 in .45 HP once and for a while I thought I had a headspace problem...
This old Colt is worn very smooth on the rear face of the rear lug. There is no peening or rough edge present, but this does open up the gap a little bit. I am hoping the Ed Brown barrel, aside from being tighter than my Mil-Spec variant, will reduce some of this clearance.
And you are correct. My hood never gets near my breechface as it is my guideblocks that are driving the barrel forward.
If I am understanding this barrel fitting thing correctly, you want around .006" to .010" of 'float' with the barrel placed inside a bare slide and if the hood touches the breechface, you should have clearance between the rear barrel and slide lugs.
Am I seeing this right in my head? That X-Ray of a 1911 at the moment of firing really helped me to envision the barrel/slide movement, but this is an area I haven't done a lot of work in.
First, let's clear up a little confusion on the headspace question.
That a cartridge rim sits flush with the hood is no indication that the headspace is good. It may well do that... but it's not an accurate assement. It's entirely possible for that to happen, and have excessive headspace. You can file .100 inch off the barrel hood... cut the chamber a .100 deeper, and get the case rim flush... but the headspace is way out of spec.
Conversely, the rim can sit above or below the hood, and the headspace can be fine.
Headspace is determined by a linear measurement from the breechface to the chamber stop shoulder with the gun in battery. This is understod to be the static headspace dimension, and only changes with wear or lug deformation.
Dynamic... or "working" headspace... is the actual headspace that a given gun has with a given cartridge, determined by the difference between the static dimension and the length of the cartridge case. Working headspace changes with every round fired, unless all brass is exactly the same length.
Excessive headspace can be dangerous or benign... depending on what causes the static dimension to be out of spec. Take a gun with minimum headspace, and cut the chamber .025 inch deeper. The headspace is now .003 beyond maximum allowable tolerances... but isn't dangerous.
Take the same gun, and cut the barrel lugs back by the same amount. The excess is exactly the same... but it's now in the dangerous category because the case backs out of the chamber until it contacts the slide when the gun fires... and the head area is unsupported by what is approaching a critical amount. While it's not likely that a low pressure round like the .45 ACP will blow a case... assuming that the case is made to USGI spec... but some commercial cases will bulge or even rupture. Even the thick GI case spec can present a problem if reloaded a few times, and the chambering round happens to index in the same weakened place 2 or 3 times.
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If I am understanding this barrel fitting thing correctly, you want around
.006" to .010" of 'float' with the barrel placed inside a bare slide and if
the hood touches the breechface
While I don't mind a little endshake... or horizontal play... I don't like to see quite that much. It mainly depends on how the tolerances stack up as to how much a good barrel will have. Barrels and slides made to WW2 era GI specs will have a little or a lot... again, depending on the tolerance stacking. A good commercial barrel... especially a match grade barrel... not so much. Maybe none.
A tight horizontal fit with the breechface means that the slide is pushing the barrel as far forward as it can go... limited by lug contact. Barrel front to slide rear. As long as there's a thousandth clearance with the barrel not under the slide's force... it's enough to prevent binding as long as the gun is reasonably clean. .003 is better for general purpose guns that may or may not be well maintained due to rough conditions.
Finally... a word on accuracy.
It's become the trend for many to demand match grade accuracy from 1911s... and to complain if the gun won't keep all its shots inside a 2-inch circle at 50 yards. Doesn't matter if the gun is runnin' like a Timex watch, with nary a bobble... if it won't knock a gnat's wings off at 50 paces... it's a dog.
While I'm amazed at the accuracy that some guys are capable of wringing out of these pistols... it's not the only standard to judge'sm on. I've never been able to get'em to shoot like that... mainly because I don't try very hard, as functional reliability is my main goal, and durability/longevity in 2nd place... with cutting cloverleaf groups at impractical distances running a distant 3rd.
I want the gun to run. Period. No matter if it's spankin' clean or filthy as a dirt road.
Dripping with oil, or as dry as a popcorn poot. Gripped with both hands like a vise, or as limp-wristed as a... well... you get the picture.
I want the fit that I work for to last. My habit is to fit tightly... slide to frame and barrel to slide... and then loosen things up a little to provide what we know as "Oil Clearance." Just like we don't need for our rod and main bearings to be too tight... we don't want the slide and frame rails to be placed in hard frictional contact. I've heard a few top gun pistol wrenches state flatly that peening rails to tighten up the fit doesn't last much beyond 15,000 rounds. I smile and nod, and change the subject. I've got a pair that have seen over 100,000 rounds each since I did the refit, with very, very little change... and I'm not anal retentive about clean and oiled.
A 1911 pistol that's built to match clearances is essentially out of spec. A singular-purpose weapon that is excellent for its purpose... but often falls flat in general purpose/go-anywhere-do-anything yeoman service. While it's possible to build a gun that does both well... it's a very exacting and expensive task. I just don't have the time, nor the inclination to mess with it. My hat is off to those who do... but it's just not my way.
This doesn't mean that I don't give a thought to accuracy. I do... but just not as much as some. Fitting a match grade barrel for general purpose use will produce groups in the 3-inch range with good ball ammo at 50 yards... and sometimes better. With good handloaded SWCs, you can cut that down to 2 inches pretty easily. As long as the gun runs... that's more accurate than it needs to be in that role.
The headspace dimension is hard for me to visualize, but your post was helpful. On this gun, a dedicated duty weapon, I want reliability to be first and foremost and I have now proven that over several thousand rounds. I am changing the barrel to reduce the 'endshake' as you say and not to influence accuracy. I can, with the Mil-Spec barrel and bushing currently in the gun right now, keep all my shots in the 9-10 rings at 25 yards offhand, which is more than acceptable to me.
I just want to be sure that I get the hood length right and maintain the 3/32" gap between ramp and chamber throat.
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The headspace dimension is hard for me to visualize
This may help a little further.
You understand the forward drag effect of the bullet on the barrel by now, and the slide/breechblock being driven backward by the equal force applied to bullet and slide.
Lock your hands in front of your chest and pull in opposite directions. The fingers of your left hand are the barrel lugs... your right hand... the slide lugs. While applying this equal and opposing force... gradually roll your fingers open so that both arms will creep apart.
This mimics the lugs deforming. As the lugs deform and allow the arms to move further apart... it creates a gap between the breechblock and the barrel. As the gap grows, the distance between breechblock and chamber shoulder... the static headspace dimension... also grows.
Remember that headspace is defined as the difference between the static dimension and the length of the cartridge case. i.e. If the static dimension is .910 inch, and the case is .890 inch long... you have .020 inch of dynamic or "working" headspace.
If the lugs have deformed to allow the original static dimension to grow by an additional .005 inch... you have .025 inch of dynamic headspace with the same cartridge.
Because the gap increases as a result of the breechblock and barrel separating by an additional .005 inch... the case backs out of the chamber on firing by that amount. Essentially, the breech opens .005 inch while the chamber is under pressure.
Back in the day of soft barrels and slides, barrel lugs were equalized... horizontal bearing... by select-fitting or light hand-fitting barrels and slides so that the first lug was bearing, and the other two were kissing a couple thousandths inch of air... and firing a few proof rounds to set the first lug back and bring the others into play. Then, any flanging on the top of the lug was dressed, and the gun was headspace gauged... proofmarked, and shipped.
That method can still be used if done correctly... but it must be done correctly... and if the lug(s) only have a half-thou or so to deform. Or... Just shoot the gun until they equalize by way of normal wear. At any rate, the first lug is the strongest and most supported... and must be the one bearing the brunt. If one of the others takes the hit, they can crack or even pull completely through to the chamber. This is why it's not really a good idea to "upgrade" to one of the hot-rod numbers like the .460 Rowland or the .45 Super with a drop-in barrel.
If we start thinking of the locking lugs as recoil lugs... it starts to make more sense. Think of the recoil lug that bears in the bedding area of a bolt- action rifle.
As far as accuracy goes... unless the guns are completely worn out junk... they're more accurate than the average shooter can prove without a solid rest... and usually more accurate than the above average shooter can appreciate in rapid fire at defensive ranges.
When the AMU was first established... and "accurizing" first toyed with... the guns were selected from new stocks of service pistols and tested for accuracy with match grade ball ammo. If the gun would shoot into 3 inches at 50 yards... it was selected for the program. If not... it was returned to the armories for service use. Many passed the test, and the ones that didn't pass didn't fail miserably. Many failed by miniscule amounts. Even a fraction of an inch over the limit failed the guns.
My personal feeling... and again, this is worth what you paid for it... is that if the gun will keep its shots inside 3 inch circle at 25 yards from the bags...it'll save ol' skinny in a deadly encounter if I do my part. If I don't... a one-inch gun won't likely serve me any better.
Thanks, Tuner, Those explanations really do make things more clear.
What should one use to measure the static and dynamic headspace?
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What should one use to measure the static and dynamic headspace?
I use a standard .898 GO gauge and ignition feeler gauges... but in a pinch, you can use a fired, resized case.
Slide off... bushing in... extractor out... place the barrel in the in- battery position with the gauge in place. From the underside, slip different feeler gauges between the GO gauge and the breechface until you find one that slides in with a little drag. Add the thickness to the length of the gauge. It won't give you a precise figure, but it'll be close enuff fer gub'mint work.
Dynamic headspace is the difference between the length of a given cartridge case and the static dimension. If the cases are all the same, the headspace will be the same. If the case lengths vary... the hadspace will vary from shot to shot.
It's rarely necessary to measure the exact static dimension. The parameters are that the slide must go to battery readily on a GO gauge, and must not go to battery easily on a NO-GO gauge. If it goes to battery on the .920 NO-GO, the headspace is deemed unserviceable.
The GO/NO-GO test doesn't determine WHY the headspace is excessive... whether it's due to a deep chamber or if it's a spec/tolerance or wear/deformation issue with the lugs. It only tells you if the headspace is within acceptable limits... or not, as the case may be. Another way, the headspace test only alerts you to the fact that something is wrong... not exactly WHAT is wrong.
It's entirely possible to have excessive headspace, and the gun is perfectly safe to fire. it's also possible to have acceptable headspace... and the gun dangerous to fire.
For this reason, I also use a chamber plug gauge that shows if the case head support is okay. If any portion of the gauge shows beyond the chamber ramp... I've got a problem. These gauges require determining the static dimension above minimum, and factoring it in to the result from the plug gauge. If the gauge doesn't stand beyond the ramp when dropped into the barrel, but the total headspace dimension proves that it will back out far enough to expose the case head... it's a problem.
SvenTunerGali... the all-seeing... predicts that you will find a static dimension of .913-.916 inch.
I have a .45 CP case marked 'FEDERAL .45 AUTO' that measures .890" OAL from face of the rim to the case mouth. I used this for testing. When seated in the barrel, the rim is .008" below the hood.
I placed this case in the chamber and installed the barrel in the slide, with the bushing in place, but with the extractor removed. With the barrel pushed forward against the slide lugs, I can slip a .023" feeler gauge between the case rim face and the breechface. Add them together and I get .913" OAL.
Now, with a new barrel with a longer hood, the chamber face will move away from the breechface, correct? How will that affect my headspacing?
Correct. Headspacing with another barrel will depend on the new barrel's chamber depth.
You get to start all over with the feeler gauges. Ain't this fun?
.913 huh? If I was any better, it'd be scary... eh what?
So, .913" static headspace is good, or at least within acceptable tolerabce, correct? How would I find the dynamic headspace measurment?
Yep. It's within the mid-spec range, and .009 inch from the maximum of .920 inch.
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How would I find the dynamic headspace measurment?
You'll have to shoot a round... resize it... measure it... and subtract it from .913 inch.
Dynamic/working headspace is the actual headspace on a given cartridge case.
If the unfired case length is .890 inch long... the working headspace in your gun with that barrel is .023 inch.
The static headspace specs in a .45 ACP pistol are from .898 to .920 inch. As long as it falls within those limits, it means that the gun will chamber the longest cartridge case that is within spec and will still fire the shortest case that is within spec.
Specified limits for cartridge cases are .888-.898 inch.
So... If you had the maximum static dimension of .920 and the shortest within spec case... the working headspace for that round would be .032 inch. If the next round that chambers has a maximum case length of .898 inch... then the working headspace for that round would be .022 inch.
The static dimension only changes with wear or damage. The dynamic changes with each case that chambers, unless they're all the same length.
My fired cases from this gun, once fired brass that is, always come out around .890" after sizing.
Here's the drawing somebody'd wanted a while ago: The vertical gap (zero to ~ 0.003") is probably kind of variable because the +13 link (291 link) will have lifted the slide about 0.003 to 0.004" up on the frame when the link is vertical and I'm not real sure where it (or the barrel) will end up vertically when they finally reach battery.
Links longer than +13 are available, but this is the longest one that won't bind up a mid-spec gun when it's vertical - at least won't bind it up too badly!
Dan's illustration shows the barrel riding/standing on the link. Note the slidestop pin not bearing on the lower lug foot.
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Dan's illustration shows the barrel riding/standing on the link. Note the
slidestop pin not bearing on the lower lug foot.
Oops! I forgot to include it, but the gap between the the top of SS pin and the lug foot is about 0.018" with the +13 link. [Edited: See below]
For Forum newcomers: These drawings contain dimensions based on the latest Army Ordnance Dep't blueprints available to me. They are not measurements taken from a gun.
[Edited: The drawing in Post #55 is badly in error. Because it is too late to edit that post, the drawing has been deleted from Photobucket and it will be replaced with a corrected one in a subsequent post. The words in Post #55 are also incorrect, so disregard them. All due to a "senior moment".]
If I install a barrel with a longer hood, will this not increase my headspace dimension? How will this effect what I am trying to accomplish?
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If I install a barrel with a longer hood, will this not increase my
headspace dimension?
It depends on the distance from the breechface to the chamber stop shoulder in that particular barrel. The hood has nothing to do with it. You can cut the hood flush with the barrel face, and it wouldn't affect the headspace one thousandth of an inch. Likewise, you could weld up the hood and cut it to hit the breechface, and it wouldn't change the headspace.
The barrel hood relationship to the breechface has nothing to do with headspace. Zip. Nada.
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How will this effect what i am trying to accomplish?
It would reduce or eliminate the horizontal play between the barrel and slide. Fitting a long hood to zero clearance with the breechface... it would push the barrel as far forward in the slide as the lugs would allow.
Ok... reducing that play is the reason for the swap!
I got my Ed Brown barrel and here is the initial report:
First and foremost, it looks exceptional. Secondly, when I drop it into the slide, it fits great. The lugs are locking into the exact same wear pattern as the old barrel. The hood barely clears the breechface, by probably .005" or so. The top leg of the hood also clears the slide on each side by about the same amount. The guide block opposite the extractor is pushing the barrel forward.
Now, to my eye, the barrel does not look like it is sitting down in the barrel bed as flush as I would like it to. The 1/32" distance between chamber throat and ramp is perfect when the barrel is pulled all the way back against the frame.
I don't care for the 'crowned' barrel, but that is just personal preference. The end of the barrel is larger than the rest of the barrel and the bushing fits very snug at the end of the barrel, however, once you slide the bushing back a short distance, the bushing gets loose and allows the barrel to link down. The bushing fits snug in the 1927 slide without modifications.
Now, here is where some fitting will need to be done...
When I assemble the pistol, without the recoil spring, I can push the slide almost into battery, but the slide stops moving forward about the last .100" of its travel. The barrel is linking down well before the slide starts moving to the rear, so the timing looks good.
Would this be the lower lugs contacting the slide stop?
I noticed that my Mil-Spec barrel sits down perfectly flush on the barrel bed, but my new Ed Brown barrel doesn't appear to fit quite as flush. Is this normal, or, something that will require work? Also, if I put the barrel on the frame and pull it back into contact with the VIS, the 1/32" gap appears to be perfect, so it does not appear that any work is required here.
I haven't had a lot of time this weekend to work with it, but the main issue I am having is the slide will not go forward into battery. It is about .100" short of going fully forward. However, the barrel fits up into the lugs nicely at the same wear points as the original did. FP hole appears well centered and the barrel links down well before the slide stops moving rearward.
The EB instructions say that you can use a 3/16" round file to increase the width of the flat on the lower lugs from .030" to .060" in order allow the slide more rearward travel. I assume they speak of the flat at the very bottom, front of the lower lugs, which contacts the slide stop pin?
Could you enlighten me as to exactly where the material needs to be removed? I would rather research twice and file once.
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The barrel is linking down well before the slide starts moving to the rear,
so the timing looks good.
You got me puzzled with this one! How can the barrel link down, before the slide starts moving to the rear?!
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Could you enlighten me as to exactly where the material needs to be
removed?
In the area of the lower lug where the slidestop pin rests when the barrel is in battery. E-A-S-Y does it. A very little bit goes a long way. When the top of the safety lines up front to rear with its triangular notch in the slide... stop and check to see that the disconnect resets correctly.
And, John is rightly concerned. The barrel can't link down before the slide moves.
Correctly timed, the slide only moves about 1/10th inch when linkdown begins... but move it must... because rearward barrel movement is what initiates linkdown. Linkdown should be complete at .250 inch of slide movement.
I guess that explanation wasn't that great, but what I meant to say is when working the slide/barrel assembly back and forth by hand with no recoil spring in place, the barrel seems to link down smoothly without any interference. I had a friend bring a 1911 in a while back that he bought from the local pawn shop and the unlock timing was very bad due to a very long link.
Dad came over last night and we were fiddling around with another 1911 I just picked up, so I showed him the Ed Brown barrel. After applying some DyeKem, I found the reason why the slide will not go into battery.
The length of the locking lug grooves on the chamber roof are different. The lug nearest the breechface has lug grooves that extend to a point almost even with the chamber's horizontal centerline. However, the second lug groove isn't as long and it is in this area where it is making solid contact with the slide. What I need to do is bring the second groove down further toward the chamber centerline. Where the Kart has 'pads' in the rearmost lug groove, the EB has a shorter second groove that seems to serve the same purpose.
What is the correct file to be used for this procedure?
I think you mean the slots between the lugs. The area that accepts the slide's mating lugs. If you need to cut one deeper into the barrel, use a pillar file with two safe sides.
Remove just a small amount of material... maybe .003 inch... and check to see if the slide moves farther forward.
I think that you may be barkin' up the wrong tree. Usually, when the barrel is jammed vertically into the slide due to tight lug fit, there's a sticky point as you pull the slide out of battery. Let it go to battery at speed and see if this sticky place exists.
Another quick'n'dirty test is to see if any vertical play between slide and frame has been removed, so that you can't move the slide vertically by forcing it up and down at the front with the gun in full battery. That indicates that the barrel is forcing the slide tightly upward against the frame rails. If it is... it's either due to the lug slot not being deep enogh... or the lower lug and slidestop pin relationship.
You have to be careful about deepening the slot because if you position the slide's lug too far from the bottom of the barrel's lug... the barrel lug loses full support. You want the slide's lug to bear in the corner... at the junction of barrel lug and the top of the barrel for greatest strength.
So... remove a minimal amount to see if the slide moves further into battery. If it does... remove a little more and check it. When any vertical play that's present WITHOUT the barrel is present WITH the barrel... stop... and go to the lower lug if the slide still won't go to full battery.
If you hold the slide up to the light, one can just see light between hood and breechface. If I push the barrel to the rear and roll it side to side, the breechface will just show some very l-i-g-h-t contact with the hood, just enought to 'polish' the Dye-Kem, but not enough to actually rub it off. This looks good to me and I have clearance on the sides of the chamber too.
Anyone have a part number for the correct file in Brownell's?
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"Let it go to battery at speed and see if this sticky place exists"
I would be afraid to do that! I pushed the slide forward with my hand and almost couldn't get it apart!
Ah! Okay. You may just need to relieve the contact area(s) a bit with a flat file. Not a critical area. The lugs don't bear recoil forces on the sides from 9 to 3 o'clock The punch is taken at the tops... between 10 and 2.
Kinda hard for me to wrap my head around these descriptions.
What is preferred:
The hood pushing the barrel forward or the guide blocks? I am getting a light touch between hood and breechface, even though you can see light through them when disassembled.
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Thoughts?
Via breechface contact with the hood.
I can see light with the slide/barrel/bushing installed, but if I push back and rock the barrel side to side, the contact will just start to polish my Dye-Kem coating away so I would say we have close to zero clearance with a "hair-to-spare."
Here's a replacement for the flawed drawing previously deleted from Post #55:
Dimensions are based on mid-spec values.