Norinco 1911 all stock with 2500 round count:
Today the slide release broke in the pin area that slides thru the frame and barrel link. Two thirds of the pin broke off and fell out of the frame while firing. I have two questions:
1. Besides just plain being a defective part, is there any other reason that would have caused this?
2. Will a replacement slide release require fitting or will most drop in?
Look at the link to see if it appears to be stretched or with an oblong slidestop pin hole.
Link does not appear to be stretched nor did the slidestop pin hole appear to be oblong. I did pull the link and check the slidestop pin hole. It measures .205 from front to back and .206 from top to bottom...
As HSMITH suggested, I did some further reading. I found your bit on stem binds. I have been expriencing stem binds. I thought it was a combination of bullet selection and mags. Bought some Metalforms 7 round roundtops. Did not seem to help stem binds and might have been slightly worse than the factory mags. Approx. stem bind percentages as follows:
Ball rounds almost none.
H&G 68 200 gr SWC 1% or less.
RCBS 82045 200 gr SWC (short nose & 2 lube grooves) 15%. As I was given
12,000 of these bullets, I hoping to get the gun to run with these.
I checked the top of the throat and the edge appears to be eased/radiused well. I could not see a noticable gap at the link/front radius area.
Could the stem binds and broken slide release be related?
A buddy of mine gave me a used slide release. It seems to work without modification. He gave me a new Wilson #2 link he had. The package states it is a .273 not .275 as you stated in your other thread.
I plan to try the fit of the shorter link unless you feel this would be too short...
#2 Link
Given the average Norinco's specs, I'll say that the .273 link will be short.
The problem with too-short links is that they tend to advance the start of the unlock sequence... which if it occurs while there's still pressure in the bore, can damage the lugs, link, and lower barrel lug. Also the distinct possibility that it won't draw the barrel far enough down to prevent the locking lugs from crashing with those in the slide...shearing the top corners of the lugs.
I doubt if the barrel riding the link around the forward radius of the lower lug would have broken the slidestop pin, though it could contribute to the excessive stem bind. Very few Norincos have feed/return to battery issues, and I'd be more inclined to think that yours is being caused by excessive extractor tension and/or a canked extractor channel or breechface guide wall width... too narrow.... or a burr or rough machine mark on the breechface itself.
If you use the #2 link, flip the gun upside down and hand-cycle it to see if it works smoothly. Any sign of a hitch in the cycle indicates that the barrel isn't unlocking. Also a possibility that the link will be too short to allow the bottom of the lug to pass over the slidestop pin... stopping it from going to battery even when empty.
See if the gun will return to battery more smoothly with the extractor removed. If there's no change, try it without the link. You may be able to narrow it down to one or the other. If neither one makes a difference, you'll need to look at other things.
I do not know what stem binding is. I can find no parts list or parts diagram for a 1911 or a 1911 magazine that lists a "stem" as a part. Please identify this part for me. I have seen barrel link binding due to the link, the link pin and also the slide stop.
I am not a Noriunco 1911 expert like 1911 Tuner but I have fitted a new #3 barrel link (.278) in mine along with a new barrel link pin and slide stop. I have seen a #2 link (short link) used when the barrel throat/bed is screwed up but have not seen it work reliabily. I do not understand why you want to use the short link.
If the slide stop fit is sloppy I would consider fitting an over size slide stop.
I would bet you got a bad part. Norincos are usually made of good hard steel.
Stem bind... aka 3-point jam. Actually a misnomer, since all Browning tilting barrel designs essentially operate with a little stem bind. Excessive stem bind is correctly called the 3-point jam which causes most failures to go to/return to battery.
For all the Norinco lovers... I'm particularly fond of the Pimpgun... Hard- chromed by Tripp with a hard-fit Kart barrel. Good shooter and gobbles everything I can throw at her. One-piece milled (early) Colt trigger installed makes it a real sweetie.
I have installed the #2 link. I cycled the gun by hand upside down with both links. Could not tell a difference between the two and no hitchs were felt or seen with #2 installed. I hand cycled some loaded rounds. Feels smoother with the #2. Dropping the slide on a loaded mag with the old link, I could feel a slight hesitation in the slide at about a half an inch from full battery. Seems a lot crisper with #2 and no hesitation... Could be my imagination though.
I am not sure how to check for excessive extrator tension.
I have no clue what a canked extractor channel is...
Could you please advise on both.
Breech face shows light machine marks but feels smooth.
Breech face guide width is .492.
Sounds like the link was contrbuting to the stem bind condition... or possibly it was an out-of-spec lower barrel lug.
Remove the extractor and clean the channel completely. Pipe cleaners and solvent will help. While the extractor is out, hand-cycle a few more rounds through the gun to see if it's better. You'll have to invert the gun and shake the rounds out... no extractor to pull'em.
Extractor in... let a round chamber at full speed. If you're using live ammo, be VERY careful. Draw the slide rearward slowly, just far enough to pull the round out of the chamber, but don't let it touch the ejector. Magazine out for this. The round should sag slightly, but not fall off the slide when shaken lightly. If it doesn't sag a bit, there's too much tension. If it falls through the magwell, there's not enough.
Now to the short link. The unlock sequence should just begin at about .100- .110 inch of slide travel. Without a dial indicator, it'll be hard to determine exactly when it starts, so fire the gun a few times and check the top corners of the locking lugs for any sign of rounding or peening.
Check this too:
With the slidestop pin through the frame and link, but with the arm hanging vertically and the recoil spring plug removed to free the spring... push the slide fully rearward and hold it. Push the barrel fully rearward and down firmly while moving the slidestop arm. It should swing feely with no binding. A very slight amount of tightness is probably okay... but so tight that you can't move the arm with a light flick of your fingernail is too much and indicates that the barrel's rearward movement is being stopped by the link instead of the vertical impact surface in the frame. This can result in another broken pin or a stretched/broken link fairly early... within about 500 rounds or so.
This is why I asked about any stretching of the link, and indicates that you may have a linkdown timing problem due to the vertical impact surface located too far rearward... or the lower barrel lug located too far forward.
This condition puts stresses on the link and slidestop pin that they weren't designed to bear, and will cause a failure in one or the other sooner or later, depending on how far out of spec these areas are. In extreme cases, it can cause the lower barrel lug to separate from the barrel... or even crack the chamber floor.
I always remove extractor and clean the channel with each cleaning. Checked cycle of rounds w/o extractor. No differrence.
Chambered round and checked extractor tension. Checks good per ur instructions.
Fired 140 rounds today with shorter link. No signs of peening.
With the slidestop pin through the frame and link, but with the arm hanging vertically and the recoil spring plug removed to free the spring... push the slide fully rearward and hold it. Push the barrel fully rearward and down firmly while moving the slidestop arm. It should swing feely with no binding. A very slight amount of tightness is probably okay... but so tight that you can't move the arm with a light flick of your fingernail is too much and indicates that the barrel's rearward movement is being stopped by the link instead of the vertical impact surface in the frame. This can result in another broken pin or a stretched/broken link fairly early... within about 500 rounds or so.
I checked this last night. I did not feel any friction while manipulating the barrel by hand. Could get some binding by placing 6 o'clock position of muzzle on workbench and pushing down. A little excessive tho I think...
Now about today... I am still getting a stem binds. The slide stops about 3/8 to 1/2 of an inch from battery. Rim of case has not quite made contact with extractor...
I quess the round might be hanging up on unseen roughness/defect on breechface. there is light vertical machine marks on the face. Your thoughts and suggestions on polishing same.
If the rim hadn't engaged the extractor yet... remove the extractor and measure the two small parallel rails on the underside of the slide. You want .484-.488 inch between the rails.
If you can get the stoppage to occur by hand-cycling, lightly bump the muzzle with a foot-long piece of wood... just a tap... to see if the gun snaps to battery.
Quote:
I checked this last night. I did not feel any friction while manipulating
the barrel by hand. Could get some binding by placing 6 o'clock position of
muzzle on workbench and pushing down. A little excessive tho I think.
Look at how far back the barrel sits in the frame pushed all the way back with the slidestop pin installed. Remove the link and check again to see how much difference there is.
Gap between rails is .492".
I got the stoppage to occur by hand-cycling but at a much reduced rate of about 7% vs. 15% live fire. Light rap on muzzle got it to go to battery every time. Just note: muzzle was a consistent 5/8" proud of the bushing on each stoppage.
Look at how far back the barrel sits in the frame pushed all the way back with the slidestop pin installed. Remove the link and check again to see how much difference there is.
No noticable difference.
Okay... Ruled out a problem with the link. The light binding isn't caused by stretching of the link. The 3-point jam/stem bind seems to be coming from the barrel either rising too early as the round tries to break over to horizontal... or the barrel itself isn't dropping completely into the bed.
Lay the barrel back into the frame and install the slidestop pin. Look to see if there's a fairly wide space between the bottom of the barrel and the top of the frame bed with the barrel pushed down and back.
Also check to see if the lower edge of the barrel throat is overhanging into the magwell. It should be sitting slightly forward of the top corner of the feed ramp... about a 32nd inch... but most Norincos that I've seen have that lower edge flush with the top of the ramp. Check for a sharp corner at the top of the barrel throat too. That can cause the side of the cartrdge case to snag and pull the barrel forward... which also tends to cause the barrel to rise early relative to the slide's position.
If all checks out okay, and the link isn't pivoting the barrel, there may be a problem with the geometry of the lower barrel lug, causing the barrel to rise too abruptly on the slidestop pin.
For Dean... who hasn't heard of stem bind and/or 3-point jam... Here's a brief description of what happens:
The cartridge enters the chamber at an angle, and drags on the top of the barrel throat at the corner. The barrel rises too early or too abruptly while the slide is pushing on the rear of the round, increasing the angle that the cartridge has to overcome in order to break over. The bullet ogive strikes the chamber roof, causing a bind at three points: On the side of the case, just below the mouth... At the bullet ogive... and at the breechface. Three points. Excessive extractor tension can contribute to the problem, but isn't a cause by itself.
The "Stem" is the cartridge itself that's in a bind at these three points. A telltale sign of a stem bind is a small, crescent-shaped mark about 1/8th inch long and about 1/8th inch below the case mouth. It can be a light mark...not much more than a scrape... or it can be fairly deep, like a small gouge and well-defined, depending on how hard the bind is. Some can actually deform the case. Most just leave a light mark. Breaking the corner at the top of the barrel throat doesn't usually cure a hard stem bind. It just "softens" the mark. Stem-binding related failure to got to battery is probably the single most frequent cause of overthroating of barrels by amateurs who don't understand what the problem is.
Another thought on the broken slidestop pin. If you haven't been in the habit of letting the slide go at full speed with the gun empty... and the new one also breaks... use a close-fitting drill rod in the frame holes to see if they're drilled straight or at an angle. If the holes aren't straight, it puts a side-load on the pin, which can cause premature failure, especially if you drop the slide on empty very often. Pretty rare, but not unheard of, and could also contribute to your return to battery problems.
Lay the barrel back into the frame and install the slidestop pin. Look to see if there's a fairly wide space between the bottom of the barrel and the top of the frame bed with the barrel pushed down and back.
My eyes are gettin" old but the fit is tight... 002 gap at best. Pretty tight fit.
Also check to see if the lower edge of the barrel throat is overhanging into the magwell. It should be sitting slightly forward of the top corner of the feed ramp... about a 32nd inch... but most Norincos that I've seen have that lower edge flush with the top of the ramp. Check for a sharp corner at the top of the barrel throat too. That can cause the side of the cartrdge case to snag and pull the barrel forward... which also tends to cause the barrel to rise early relative to the slide's position.
Lower edge is not quite flush but pretty close... I'd say within .010. Definitely not overhanging. Top edge of throat appears to be eased nicely.
Do one more little test. Lock the slide back and lock a mag into the well with one round in it. Lightly push the muzzle against a table edge and hand- cycle the round into battery. My bet is that it'll slide in like greased goose poop.
If it does, your barrel is rising too abruptly relative to the slide's position.
If you're using live ammo... use all due care.
Slight glitch
SSSLLLLLOOOOOWWW hand-cycle there is a slight hesitation and occasional hang- up as cartridge stops forward motion from mag. Moderate to fast cycling was slick.
I took the barrel and held it in place on the frame. Inserted mag with one round. Slide cartridge forward with finger and appears the meplat is is hanging on feed ramp. Ramp is reasonably smooth. Do not know if this has anything to do with it...
Also check to see if the lower edge of the barrel throat is overhanging into the magwell. It should be sitting slightly forward of the top corner of the feed ramp... about a 32nd inch... but most Norincos that I've seen have that lower edge flush with the top of the ramp. Check for a sharp corner at the top of the barrel throat too. That can cause the side of the cartrdge case to snag and pull the barrel forward... which also tends to cause the barrel to rise early relative to the slide's position.
I appear to have been mistaken on the throat overhang... there is slight overhang of the throat's lower edge into the magwell when barrel is pushed back and down on frame. Not a lot but enough to catch my fingernail on. Many apologies for my oversight...
Eureka! We may have nailed the reason for your feed/return to battery problem.
The slight catch as the round moves forward in the mag is probably due to the raised dimple on the follower snagging the case rim. That means that it's doin' its job.
The standard fix for barrel overhang into the magwell is to file across the lower edge of the barrel throat at a slight angle to get the clearance, and reshaping the throat. Since Norinco barrels are hard-chromed, that presents a problem. A file won't cut it, and it'll have to be ground... along with the reshaping procedure. The other part of the problem is that... once the chrome plating has been breached, it will eventually start to peel and/or flake off. The good news is that the plating on the Norinco barrels is pretty good and probably won't start to peel for a long time.
The problem is that the incoming round strikes the barrel throat (actually the barrel ramp) early and low instead of being deflected upward far enough by the corner of the frame ramp. The round drags on the barrel ramp, and pulls the barrel forward with it as it feeds instead of the slide initiating the barrel's forward movement at a later point... after the cartridge rim has gotten under the extractor and begun the breakover into the chamber. As the barrel moves forward, it also moves up. As it moves up, it increases the angle that the feeding round has to overcome in order to enter the chamber... and gets caught in the classic Three-Point Jam... aka "Stem Bind."
Your options are to LIGHTLY grind the lower edge of the barrel ramp to get it ahead of the frame ramp corner, and use a fine grinding stone in a Dremel to LIGHTLY roll the flat edge that's left. (Can ya'll believe that I'm actually advising somebody to use a Dremel?)
If, on the other hand... the overhang is the result of somebody rounding the top corner of the frame ramp off... you've got a problem. Maybe salvagable if it's not too far gone... maybe not. If the frame has been altered beyond a certain point, it'll require machining and a steel insert like the ones that some shops install in alloy frames to prevent damage and wear. It's not a cheap fix.
Gun is stock, so I am hoping the frame ramp is in spec. Does not look like it's been altered.
Just a side note... I measured the #2 link I put in after firing about 150 rounds. The slidestop pin hole might have stretched about .003. It measures .205 front to back .208. I did not measure before use.
Also, both links, #2 and original no measure the same from outsde to outside of both pin holes...
.456". Could be inconsequential.
I took the throat back to what I thought was flush with the feed ramp. Fired 160 rounds. First 6 mags went off without a hitch. Then I experienced 4 stem binds in the remaining shots. Much much less that before. Got home and checked fit again. Still had very slight overhang as evidenced by barely catching my fingernail. Took slight bit more off and will try later.
Did notice one thing about the fit of barrel to frame...
Quote:
Look at how far back the barrel sits in the frame pushed all the way back
with the slidestop pin installed. Remove the link and check again to see how
much difference there is.
No noticable difference.
Checked again and there is about .010 movement to the rear with pin/link removed. Did not notice this until closley checking fit...
I do believe we have gotta er nailed down tho.
Might be a few days before I can try firing it again. Will let ya know tho.
I took the throat back to what I thought was flush with the feed ramp. Fired 160 rounds. First 6 mags went off without a hitch. Then I experienced 4 stem binds in the remaining shots.
Check for the crescent-shaped mark on the side of the case to see if it's still in stem bind.
And:
Checked again and there is about .010 movement to the rear with pin/link removed. Did not notice this until closey checking fit...
If the barrel is moving that much without the link and pin, the link is stopping the barrel under tensile stress... stretch... puts a load on the link and pin that could cause another failure. Go back to the .278 link and check the movement/difference again.
That barrel movement was with the .278 installed.
Yep, crescent mark is there.... many a piece of my brass bears that ugly scar.
Quote:
Yep, crescent mark is there
Okay...
The mark indicates that the barrel is linking up too early or too abruptly, while the round is still trying to break over. Excessive extractor tension can be a player here. Try taking just a bit of tension off after your finish with the BOTTOM EDGE OF THE BARREL RAMP.(Not yellin' at you, Homer. Just wanted to make sure that it's not misconstrued by some who may not understand what that lower edge position relative to the frame ramp means)
Does the barrel ride the link at any point before vertcal/in-battery position?
If it doesn't, the forward radius of the lower barrel lug may be out of spec, causing the abrupt rise.
Back to the main problem... the broken slidestop pin.
When the barrel unlocks and links down, it should be stopped by the vertical impact surface in the frame rather than by the link. If the link stops it's rearward movement, the link starts to stretch, and it will continue until the barrel is either stopped by the VIS, or it breaks. This effectively lengthens the link, and delays unlock and linkdown timing... possibly to the point of upper lug damage due to the barrel nod dropping early enough to avoid a crash with the lug corners in the slide. If it should stretch to the breaking point, and lets go when the gun is fired, the lugs crash hard... upper locking lugs AND the lower barrel lug. Cracking and/or shearing is the eventual result of that one hard crash.
Meanwhile, this also throws shear stresses on the slidestop pin and the small pin that ties the link to the barrel lug, usually causing the hole to wallow out, further delaying barrel linkdown timing.
In these cases, sometimes a slightly longer link is called for, along with small adjustments to the top of the hole to relieve the barrel riding or standing on the link... but .010 inch more rearward travel with the link means that it's probably too much to correct with a longer link. As a rule, if you have to go more than .003 inch in either direction, you probably need more than minor surgery can correct.
Sorry for the delay... been busy. Had a chance to fire about 200 rounds. With the modification to the lower edge of the throat, the incidence of stem binds has dropped from about 15% to 2-3%. The brass I've been using has been beat up pretty bad... loaded 27 times so far. I have aquired some once fired and will be trying that soon to see if that makes a difference.
Quote:
In these cases, sometimes a slightly longer link is called for, along with
small adjustments to the top of the hole to relieve the barrel riding or
standing on the link... but .010 inch more rearward travel with the link means
that it's probably too much to correct with a longer link. As a rule, if you
have to go more than .003 inch in either direction, you probably need more
than minor surgery can correct.
What kinda major surgery will be required?
Quote:
With the modification to the lower edge of the throat, the incidence of
stem binds has dropped from about 15% to 2-3%.
Okay... We've at least got it headed in the right direction. Maybe we can continue without further interruption from TWKLBTM.
On the lower edge that you set forward... It would have left a flat leading edge just forward of the top of the frame feed ramp. Did you blend that corner into rest of the barrel ramp, or leave it? If you did blend it, did you blend it enough? If you left it square and vertical at the face, it needs to be smoothed and matched as closely to the rest of the barrel ramp as you can get it without lowering the TOP corner of the barrel ramp or cutting it deeper into the chamber. This is the tricky part in barrel ramp/throat work.
On the vertical impact surface to rear of the lower lug issue... If the lower lug location is the issue... and given the Norinco barrels that I've seen, I suspect that it is... you'll have to rebarrel it. Cross your fingers that it's the barrel specs and not the frame's. Borrow another barrel from someone and try it in the Norinco... preferably a factory Colt or Springfield barrel... and do the slidestop bind test again. If the slidestop pin is free of any binding, you're golden. A new barrel will likely solve it.
I did not blend the throat from the bottom edge to the top. I'll give it a whirl. In the mean time I'll try n locate another barrel.
I'd consider something other than another Norinco barrel. The pistol's specs may play a role via tolerance stacking... and you'd wind up with the same or similar situation.
I have only fired 80 rounds since blending the throat. No binds.
Went to a local gun show Sunday. Could not find any new/used barrels. Couple guys did let me dry fit a couple of barrels from their guns. Both fit good. Even with my old eyes I could see adifference in the lower lug placement on my barrels compared to the others. My lug was definiely mor forward than the other two. Looking at Brownells for replacement.
Outstanding! Good job.
What was happening was that the bullet ogive was hitting that corner and pushing the barrel forward as the round tried to enter the chamber. When the barrel moves forward, it also moves up. If it moves up too early or too abruptly, it puts the round in a bind at three points... The round... the stem... is caught at three points, and can't continue if the bind is a hard one.
The area that you relieved doesn't support the case head at all... so you can put that bit of misinformation to rest.
Now... on to the second problem..the one that set the barrel ramp too far back to start with. For a quick and easy fix, I've had very good results with
Springfield's stainless service barrels in Norincos. Not a fitted barrel, but not exactly a drop-in either. Light fitting at the hood length was required on two pistols. I've heard that Springfield has stopped offering the barrels... so aftermarket may be your only route.
Appreciate all ur help. I am checking into another barrel. Will let ya know what I come up with.
Mighty welcome, Homer. I wouldn't shoot it much with the link stoppin' the barrel like that. Might stretch/bust the link or another stop pin.
I am unable to find any used barrels. I am looking at Brownell's for replacement. I noticed some "drop-in barrels" listed. What kind of fitting could I be looking at if the "drop-in" is not so drop-in? Would you recommend the mil-spec for for $100 or should I spring for one of the name brands...if so got any favorites?
Homer, I haven't used any of the Drop-ins in Brownells for any of my guns so I can't give ya a call on it. One guy that comes down from Tennessee to see me a couple times a year picked up a Nowlin drop-in and brought it to have me chack the fit in a couple of his guns. It needed fitting in one, but dropped into another one nicely... and he reports that the gun is a good shooter.
I did have occasion to try two of Springfield's stainless drop-in service barrels in two Norincos a while back, and they worked out well... and even required a little fitting at the rear face of the hood and in the lug slots... but when they were in the two guns, were tight and provided better than 90% vertical engagement in the slide... and both engaged on the number one lug... with one gun/barrel combo engaging on lugs 1 and 2. Headspace could have been better, but at mid-spec was perfectly adequate for what I wanted to use the guns for. I heard that Springfield isn't selling the barrels to the public any more... but haven't checked on it. I got these two from an individual for a hundred bucks for the pair... which was a little over half-price.
Hard to say what kind of fit that you'll get with any drop-in. Too many variables in the slide and in the slide/frame vertical dimensions to predict.
Wonder if that new Colt barrel I got would fit? Wouldn't cost no $100. PM if you're interested.
Is it probable you could talk me throgh fitting a barrel or best left to a smith?
Homer asked:
"Can you walk me through a barrel fit?"
Probably not. It depends on what sort of fit that you want.
Barrel "fit" comes in different degrees. There's "Drop-in" fit, which means that all dimensions and tolerances allow the barrel to physically fit inside the gun and function to a workable degree. This is essentially the sort of fit that all production guns have until you get into the high-end price ranges like Wilson and Baer. This could also be termed as "Ordnance" fit.
There's "Semi Drop-in" which includes the fit-down method. The Kart Easy-Fit barrels are of this type, and it's a pretty good system assuming that the gun is mid-spec. The main problem with many Norinco pistols is that they tend to be a little "tall" and don't allow for full vertical lug engagement with the fit-down method. Not a major problem... IF... the lug location specs get the #1 lug bearing the load horizontally... AND... the vertical depth is at least 85% of the lug's height... AND... you don't use a lot of hot-rod ammo. Which leads us to the other unknown. Unless you gauge the slide to determine where the lugs are located, you don't know which lug(s) are horizontally engaged.
The Kart Easy-Fit comes with raised pads in the slot between the first lug wall and the second lug, plus an overlength hood. It's a very good system, but it assumes that the first and strongest lug will be the one absorbing the stress loads of firing, when in fact, it may not work out that way. When the hood is cut to fit, it may be bearing on lug #2 or even #3, which don't afford the strength of #1. If it happens to be 2 or 3, AND you only have about 70% of the total height (vertical engagement) of the lug... the strength of the lockup isn't what it should be. The gun will still work, and it'll perform pretty well, but it won't hold up under hard use for as long as it should with a full contact barrel fit.
Since buying the equipment for gauging the slide and correctly fitting the barrel is an expensive proposition unless you plan on doing several fittings... it's probably best left to a smith who understands how to do it. The Kart Easy-Fit provides enough leeway to easily adjust for two lugs engaged, which... even with less than 100% vertical depth fo engagment... is much better than only one lug bearing the load.
The true hard-fit barrel has the necessary dimensions to allow the installer to fit for full vertical depth, and equal horizontal lug engagement on all three lugs... and a semi-finished chamber that allows final static headspace to be set at near-minimum specs. This type of fit produces top acuracy...a ssuming that the lower lug is correctly fitted... it affords the full potential lockup strength that the design has to offer.
If all you need is a knock-around shooter that'll work and provide acceptable accuracy for general-purpose use... ordnance fit will do.
It worked for hundreds of thousands of USGI pistols and most of the commercial pistols that have been produced since then. Some are very accurate. Some are so-so. Most fall somewhere in between.
If you want upgraded accuracy and better lockup than ordnance fit provides... with the potential for wicked accuracy if the spec gods are smiling on you... the Kart easy-Fit system is hard to beat. Just order the barrel and kit and follow the directions.
If you want the top-end... the Cadillac... pay a smith to do a full hard fit for you and request equal lug engagement.
It only takes money.
Compared old to new barrel. Old barrel has lower lug mounted about a 1/32 more forward on the barrel than the new one. Old barrel slightly overhung fedd ramp. New barrel sits about 1/32 forward of feed ramp. Checked barrel in slide. Gap between hood and breech is slight but even. Barrel installed, cycles fine. Barrel is tight at battery. Checked tension of slide release pin while hanging down, with recoil spring removed and slide to rear by pushing barrel back and down. Slight drag on on release but not a total lock-up as I had with old barrel.
Anything else I should check before firing her up?
Make sure it links down far enough to clear the upper lugs. If it does it sounds like it is good to go try out to me.
Howdy Homer... Sounds like you may be good to go.
The Norinco barrels seem to have that lower lug issue in common. Most aren't far enough forward to cause the problem that you had... but some do.
Good that the problem wasn't the vertical impact surface location. That woulda been bad JuJu.
As HSMITH noted, check to be sure that the barrel clears the slide when the slide is .250 inch out of battery with a minimum of .010 inch gap. I like .015 better, but .010 will do as long as the barrel drops early enough. With the average Nork vertical dimensions, the amount of clearance shouldn't be a problem... which brings us to the other possible trouble spot.
Since the Norinco slides tend to sit a little too "tall" in the saddle, the vertical lug engagement may not be all that great. I've seen a few with as little as 50% engagement... and if that's only bearing on one lug horizontally, premature lug deformation and setback will occur.
Gun assembled, pull the slide about halfway out of battery and insert a 1/8th thick shim of some description. A set of ignition feeler gauges stacked together will do. Lacking that, you can whittle a popsicle stick to fit the breechface. Let the slide snap forward with the shim between the hood and slide. Use a dial caliper to measure the distance from the top of the slide to the top of the barrel hood. Pull the shim and let the slide snap into battery, and measure again. Be careful to keep the caliper square on the slide and barrel to prevent a false reading... Might be good to take three measurements and average the total. The difference between the two dimensions is the amount of vertical lug engagement.
Ideally, you want all you can get with all three lugs bearing in the horizontal plane... but don't hold out hopes for that. Very few drop-in fit barrels provide full depth OR equalized lugs. The lugs are (optimally) .050 inch high, so .040 inch is 80% engagement. .035 inch is 70% and so on. You want at the very least, 80% of full depth. If you have horizontal engagement on #1...the strongest and most supported lug and 80% depth... the barrel will do pretty well for several thousand rounds. Keep an eye on the barrel lugs for signs of "stair-step" deformation on the front corners. If it's there, you'll notice a light flange on the top of the lug(s) first. That means that the lug is being slap-seated and the headspace is growing by the amount of deformation.
You might want to determine what the static headspace is before you fire the gun, just to be on the safe side.
There are two ways to determine which lug(s) are engaging horizontally. The best method is to gauge the slide and the barrel to see where the lugs are located, and how they match up. The other... the "Field Expedient" method, is to carefully polish the bluing off the front faces of the barrel lugs and color them with a Sharpie marker and go shoot the gun. Be sure that the lugs are dry and free of oil to prevent a false result. The lug(s) that come out clean after about 20 rounds shows which is/are doin' their job and which is/are kissing air when the pressure hits'em.
If your gun doesn't happen to meet the criteria for good lug engagement in both planes, but has safe headspace and functions well, it doesn't mean that it's dead in the water. It's still serviceable... It just won't hold up under hard use. At that point, you can decide whether you want to delegate it to the class of "Carried a Lot and Seldom Shot" or have it repaired. Repair involves swaging the frame rails down and refitting the slide... which, correctly done... lowers the slide a few thou and allows more vertical lug engagement. From there, you may want to look at having a new "hard-fit" barrel installed in order to optimize the whole shebang. I've had to do this with two of my Norincos. Time-consuming, and expensive if you don't do the work... but the results are very good.
Gauging the barrel is pretty simple. Measure from the fce of the hood to the front face of each barrel lug. The slide requires an adjustable fixture that wedges between the breechface and the rear face of each slide lug. Set it, pull it out, and measure the distance. That lets you determine which lug will come into play first when the hood is cut to let the barrel into the slide. If it happens to be the first lug, you can go with that. If it's the second lug, you can face the lug back until the numbers let the first lug hit at the same time.
I don't like to take more than .005 inch off the adjusted lug face. Then... if tthat brings the third lug to within reach(within about .002 inch)... face the other two back the required distance to bring all three into play, or leave it alone and let the lugs gradually equalize with use as the other two seat and set back. With two lugs bearing the load, that'll take a long time with standard ammo.
For what it's worth... Many smiths fit to the first lug only, and as long as the barrel has good vertical engagement, it'll do nicely for standard-pressure .45 ACP ammo. Your .044 inch is 88% engagement... and that's probably as good or better than your average factory pistol. Full lug equalization isn't absolutely necesary, but it does provide all the strength in the lockup that the gun offers. Trying for equalized lugs isn't recommended unless you start with minimum static headspace because as you face the lugs back, the headspace grows by a like amount. .005 inch lug setback equals an extra .005 inch of static headspace.
Ordnance static headspace measurements are .898 minimum and .920 maximum.
Lacking an adjustable fixture, I measured the slide/barrel by eye.... with calipers of course. I am assuming the first lug is the one closest to the muzzle? I belive this setup might be bearing on the second/middle lug by .002. Do you feel that this is excessive?
Homer posted:
Lacking an adjustable fixture, I measured the slide/barrel by eye... with
calipers of course.
I'm tryin' to get my head wrapped around how ya did that...
And:
quote:
I am assuming the first lug is the one closest to the muzzle? I belive this
setup might be bearing on the second/middle lug by .002. Do you feel that this
is excessive?
Nope. The third one is closest to the muzzle. If you'd gauge all factory slide/barrel combos precisely, you'd find that the bigest majority do bear on the second lug only. By .002 inch... do you mean that by hitting the second lug, the others are kissing .002 inch of air? (Assuming that your dimensions are correct... which I don't see how they can be.)
I'm tryin' to get my head wrapped around how ya did that... I can have that effect on people...
Measurement of barrel was using Vernier calipers OD jaws. From face of hood to front face of lugs.
Measurement of slide was using ID jaws of calipers. From breech face to rear side of lug.
Slide Barrel
1st lug 1.330 1.303
2nd lug 1.654 1.629
3rd lug 1.982 1.955
I believe I am dead on barrel measurements.
Had to slightly cant calipers to get slide measurements... but got consistant readings.
I will admit, I am easily corn-fused and could have misunderstood your instructions.
The numbers:
Slide Barrel
1st lug 1.330 1.303
2nd lug 1.654 1.629
3rd lug 1.982 1.955
***********************
Okay... Assuming that your measurements are accurate, the #2 lug will be the one under the load, with the other two kissin' .002 inch worth of air. That's actually not too bad, considering that in time, the bearing lug will probably set back far enough to let at least one of the others come into play. On the downside... by the time that happens, the headspace will increase another .002 inch. If it's well within spec, it won't be much of a problem... but if it's close to max, it could be an issue... depending on a couple of things.
If you have a set of small feeler gauges, you can determine how much horizontal play the barrel has in the slide. Just keep increasing the thickness until the gauge is fairly tight between the hood and breechface. It won't be exact... but it'll be close enough for gub'mint work.
Did fire about a box with the new barrel. Checked the slide and barrel and there appears to be some wear on the blueing on the 2nd barrel lug. Have not checked it with go/no go gauge... gotta get with my buddy on that. Left the gun at work, so I will have to check horizontal play this weekend when I go back.
Okay... Looks like your measurements were pretty accurate. Good show!
When you have the headspace gauged... remember that even if it's close to max, it doesn't necessarily mean that the pistol is dangerous to fire. Headspace can be excessive in two directions, and chambering a NO-GO only means that the total distance from breechface to stop shoulder is beyond ordnance limits. It can be excessive because of excessive space between rim and breechface that allows the case to back out of the chamber under pressure to the point that the area forward of the case head becomes unsupported by the chamber... dangerous.... OR... because the chamber stop shoulder has been cut too deep into the barrel... not dangerous... or it can be a combination of a little of both...which is actually dimensional tolerance stacking against you. Most pistols with excessive headspace is due to this stacking, and a more detailed evaluation is required to determine whether it's safe to fire the gun.
Excessive in the non-dangerous direction... chamber depth... only means that primer ignition won't be as positive. Erratic ignition may result... or misfires with hard, tough primers is possible, but not likely unless it's really bad.
Erratic ignition isn't conducive to top accuracy, but in an ordnance-spec pistol, you'll never really see the difference.
Excessive in the dangerous direction is a problem. Your first sign will be cases bulged ahead of the web... and even a slight bulge is cause for concern.
If you see it... stop firing the gun and have it tended to. Some brands of brass will show the bulge more readily. If you don't get a bulge with Federal brass, the headspace is probably okay. Winchester and PMC brass is thick and tough and won't bulge unless the headspace is way beyond the point of dangerous.
Horizontal play is about .007".
Measured with slide off frame. Starts with about .008" gap between hood and breach. Slide barrel forward and I get .015".
Have not had a chance to check go/no go yet.
Question: What regulates the fit/position of slide to frame? With my old barrel, the slide sat slightly forward off the frame when in battery. With new barrel, the frame and slide mate up flush... as viewed at rear of slide/frame area.
Homer asked:
With my old barrel, the slide sat slightly forward off the frame when in
battery. With new barrel, the frame and slide mate up flush.... as viewed at
rear of slide/frame area.
Generally, the specs at the rear radius of the lower barrel lug determine how the slide and frame mate at the rear...but a tolerance/spec issue between the slide and barrel locking lugs also figure in. In an ordnance-spec pistol, the barrel is pushed forward by the slide striking the hood, causing the barrel to cam up on the lower lug, or pivot up on the link...if improperly fitted. With clearance between hood and breechface, the slide's locking lug engagement with one or more of the barrel's picks up and carries the barrel into battery the last little bit...and stops as the lower lug hits the slidestop pin.
BTW how did the horizontal play look?
Well... .015 inch is a little more than I'm comfortable with. Many factory Colts have as much as .010 or .012 though, and seem to fare pretty well.
I like to see a maximum of .005 inch but there aren't many production guns that are that close unless you go with semi-customs like Wilson, Baer, and Brown etc. Baer takes it to the other extreme, and actually fit them too tight for best go to/return to battery reliability until they've had a thousand or more rounds through'em. Easy to address with a little slurry in the locking lugs and 150-200 hand-cycles though.