Barrel fitting confusion. Barrel bed or impact surface?

original: forum.m1911.org
Retrieved: December 07, 2011
Last Post: November 05, 2008

Suburban
5th October 2008

I test fit a Kart Easy-Fit barrel, and I seem to be in this situation.

The bottom lug of the barrel will not touch the impact surface of the [Caspian Basic] frame. The bottom of the barrel is making hard contact with the barrel bed, frame bridge, or whatever it is that you call the horizontal area forward of the frame ramp. There is very little gap between the frame ramp and the rear edge of the barrel throat, i.e. no 1/32" gap, but I'm not too concerned with that just yet.

It seems, according to Jerry K's 1911 Manual, Volume I, that this should be okay, as long as the slide clears the top lugs, and specifically cautions against lowering the barrel bed, as it will ruin the frame. In Volume II, the Schuemann 1911 timing bit says this situation, the barrel bottoming out on the frame, can cause a broken link or bottom lug, and the barrel bed needs to be lowered.

Sooo... is one wrong, or are these just two different ways to skin a cat? Fit the barrel per the Kart instructions, and see how things work out? I'm afraid that if I start filing on the frame or the barrel, that I'm going to find out that one or the other is out of spec and non-returnable.


Suburban
5th October 2008

Quote:
Fit the barrel as Kart states...

Yeah, I guess Kart can't fault me for following the instructions they printed.


Hawkmoon
5th October 2008

The condition can (and probably will) result in a broken link or a broken barrel lug because the barrel is supposed to stop its rearward travel when the vertical face of the barrel lugs hit the vertical surface of the frame. SOMETHING has to stop the barrel. If the lug doesn't get to the frame, what's stopping it is that the link is being put in tension. This may break the link, or it may break the lugs, or it may shear the pin, or it may wallow out the hole.

How does the barrel fit the frame w/o the slide stop pin installed? If the barrel moves farther back, and doesn't leave any gap between the frame ramp and the barrel throat, then IMHO there's a problem.

Remember that the frame ramp is on an incline. If you lower the frame bed, you also move the lip of the ramp back. That might gain you enough to allow you to use a longer link, which is what it sounds like you need.


niemi24s
5th October 2008

There is nothing wrong, IMHO, with the barrel making contact with its bed in the frame provided the barrel first contacts the VIS.

You said the lower barrel lugs do NOT contact the VIS. It is absolutely imperative this be corrected.

The simplest correction method is to install a longer link - provided it still pulls the upper lugs out of engagement with the slide.

What do the Kart Easy-Fit instructions say to do to obtain VIS contact?


Suburban
5th October 2008

Quote:
What do the Kart Easy-Fit instructions say to do to obtain VIS contact?

Nothing. The instructions seem to assume ()*() that the bottom lug will hit the VIS. There is only a passing mention of VIS contact in the "intro to barrel fitting" part of the instructions. There's no mention of frame bridge/barrel bed contact at all. There's no mention that there's supposed to be the 1/32" gap between the frame ramp and barrel throat. Instructions really only cover fitting the hood extension to the slide, and filing the contact pads on the rear lug.

Barrel comes with a pre-fit link and pin, BTW.


niemi24s
5th October 2008

Quote:
Barrel comes with a pre-fit link and pin, BTW.

The link Kart supplies with each of these barrels is probably the correct link for most guns, but it may not be the correct link for your gun.

Before deciding on a course of action to obtain VIS contact, I'd recommend taking some measurements to find out what (if anything) is out of spec. The basic barrel and frame dimensions are contained in the blueprints in our Technical Issues section.

One not contained in the frame blueprint is the distance from the top of the frame down to the bottom of the barrel bed. It has a mid-spec value of 0.077".

Probably, the most useful measurement on the assembled gun would be the gap between the barrel's lower lugs (feet) and the VIS. Unfortunately it is very difficult to do. You may have some luck using Plasti-Gage. This measurement would give you some idea how much longer the link would need to be.

Any idea what size link Kart supplied with the barrel?


log man
5th October 2008

The Kart Easy Fit is designed to give fitted barrel results as best it can. I feel that while it probably works pretty well as a replacement barrel for production guns it falls short of the versatility of a Kart gunsmith fit. Without a doubt this is just an opinion by me as I have never been tempted to use one, as full fitting is the obvious way to go, no short cuts.

Things to consider with this barrel as I do understand the premise of it and the procedure for fitting it. The link is a standard (.278") and is the correct one for the lower lug as it is supplied. A longer link will change things in a negative way as the barrel will now be riding the link instead of the feet riding the pin as this barrel was designed and intended.

Careful consideration must be given to the whole picture. Noting that the lower lug isn't hitting the VIS to begin with is good and I would immediately check what the clearance between the top of the barrel and the inside of the slide was when the barrel is pushed back and on the bed. We know that IT should be .010" at an absolute minimum, and .015" is the goal number. If it is less then .010", then the obvious direction to take is to lower the barrel in perhaps several ways. And since it isn't hitting the VIS removing material from the bed will correct two fitting goals. While it is frowned on and yet suggested even in J.K.'s manuals the area of the barrel on each side of the lower lug that is hitting the bed can be worked down a little to gain this clearance also. Grinding the underside of the barrel is not my first choice, but can be seen on many production gun barrels as the method they choose.

As I recall Caspian frames have been a common candidate for bed lowering. Take off small amounts and check often to check progress and to assure that what you are doing is taking you in the right direction.


log man
5th October 2008

Not riding the link is the whole point of this barrel's design. And, it is intended to be a hard fit barrel, also, as the 'fitting pads" are there just for that purpose. To fit this barrel so that it is standing on the pin and contacting the upper lugs (via the fitting pads) when in battery.

A much less expensive barrel could be bought for the purpose of building to mid-spec USGI M1911A1 than a Kart Barrel. I could very well mistaken , but I didn't understand the OP to have the desire to build anything less than as accurate a gun as he can , I think that's the point, isn't it.


Hawkmoon
5th October 2008

Quote:
It seems, according to Jerry K's 1911 Manual, Volume I, that this should be okay, as long as the slide clears the top lugs, and specifically cautions against lowering the barrel bed, as it will ruin the frame. In Volume II, the Schuemann 1911 timing bit says this situation, the barrel bottoming out on the frame, can cause a broken link or bottom lug, and the barrel bed needs to be lowered.

It isn't the only place where Jerry K. contradicts himself. On page 103 of Vol. 2 he shows a photo of a blown-out barrel, and he specifically attributes it to the barrel stopping on the link.

Also, read item #5 starting on the bottom of page 102 of Vol. 2 and continuing to the top of the next page. In that, he specifically states that the barrel should stop with the vertical face of the lug striking the impact surface, NOT on the underside of the barrel.


niemi24s
5th October 2008

Quote:
Not riding the link is the whole point of this barrel's design. And, it is intended to be a hard fit barrel

Oops! Didn't know (or remember) that. Sorry for the extraneous blather.

After posting this I shall delete my previous post.

Thanks for setting me straight on the Kart Easy-Fit.


niemi24s
6th October 2008

What are these distances on your frame?

* Frame top down to bottom of barrel bed
* Frame top down to center of SS pin hole
* Center of SS pin hole aft to VIS


berkbw
6th October 2008

Exactly what my points might have been. There are no "drop-in" parts sayeth John. And he's by history, and obviously, correct.

Don't smoke weed and build 1911s to shoot.


niemi24s
6th October 2008

Quote:
...he specifically states that the barrel should stop with the vertical face of the lug striking the impact surface, NOT on the underside of the barrel.

While I don't have either of J.K.'s books, I think what he's referring to is the stoppage of just the barrel's rearward component of motion - not the stoppage of both the rearward and downward components.

Because the link is in tension when pulling the barrel down, if (as designed) the VIS gets hit first (before the bed) the barrel's as far aft as it can go. It's rearward component of motion is halted. The 0.010" of play in the link system from tension to compression then allows the barrel to fall straight down to the bed. This final bit of downward motion folowing VIS contact is a little over 0.002" for a mid-spec M1911A1.

If, on the other (not good) hand, the barrel hits the bed before the VIS both the aftward and downward components of the barrels motion are halted simultaneously. This is because the link is in tension and it's stopping the rearward motion instead of the VIS. The barrel's on the bed so it can't go lower. The link's in tension so the barrel can't go farther aft along the bed - at least until the link breaks.

In short, the aftward motion should be stopped first (by the VIS), and then the downward motion (by the bed). A two stage process of hitting the VIS first then falling to the bed.

At least that's the way I think this thing works.

Maybe J.K. just didn't use the right words in his book. Can't say as I don't have either of them - yet.


Hawkmoon
6th October 2008

Dan, according to my understanding you are correct. First the rearward motion stops when the underlug hits the VIS, then the downward motion stops when the underside of the chamber hits the frame bed.

That isn't what Jerry wrote in Vol. 1. On page 65 he wrote:

"4. If the barrel links down into frame position without lug contact, and about 1/32" of the frame's barrel bed remains between the barrel and where the frame ramp begins, the barrel, link and frame are properly mated. ..."

On the next page, in discussing bottom lug fitting, he again wrote:

"3. Remove .002" at a time, until the barrel just links down into full contact with the frame bed. The rear lug face should not be in contact with the frame at this point."

Both of the above statements are in direct opposition to what he wrote in Vol. 2, and to what everyone who has discussed link-down seems to agree is the way it's supposed to work.


niemi24s
6th October 2008

Thanks for taking the time to quote those passages and to confirm I had the linkdown sequence correct.

That's the way I had it figured out from the blueprints when analyzing Schuemann's timing tests a year or so ago.

Don't know what the linkdown sequence is supposed to be (or what JMB's intentions were), but that's how it will be if all the parts are mid-spec on the Army blueprints.


Suburban
6th October 2008

* Frame top down to bottom of barrel bed - .075"
* Frame top down to center of SS pin hole - .461"
* Center of SS pin hole aft to VIS - .4405

These are measured as best as I can with a Mitutoyo digital caliper, a stainless steel straight edge, and a Wilson slide stop. I did take into account the fact that the slide stop pin is smaller than the hole.

p.72 of J.K. Vol.2, that last measurement is listed as .431 +/- .005", though I can't find it on the Browning print.

I'm gonna be really upset if it turns out that the frame is no good. I waited 8 (censored) weeks for it, and paid $50 for the transfer.


log man
6th October 2008 Oh, this can be frustrating, If it's not to much trouble how much clearance is there between the top of the barrel when it is on the bed and the inside of the slide. I just checked the only Caspian frame I have and the VIS to center of SS is .4400", a Colt Gold Cup was .4405" and an STI is .4450" so I say there's a lot a hope to be had. It's just which direction to go and not mess it up.
Hawkmoon
6th October 2008

I have a book of Ordnance Dept reprints, and their drawing for the receiver group (dated 1936) shows that dimension as .431 + .005

For top of rail to center of SS hole they show .450 - .005

For top of rail to barrel bed they appear to show .077 (but only as a derived dimension, I can't find it actually called out anywhere. They show .373 - .005 from the centerline of the SS hole up to the barrel bed. Subtract .373 from .450 and you get .077)


niemi24s
6th October 2008

Quote:
* Frame top down to bottom of barrel bed - .075"

Calculated spec for this is 0.077 +/- 0.005", so according to you measurement this is within spec.

Quote:
* Frame top down to center of SS pin hole - .461"

The spec for this is 0.450 - 0.005", so according to your measurement the hole is 0.011" lower than allowed by the spec. That's a LOT!

Quote:
* Center of SS pin hole aft to VIS - .4405

The spec for this is 0.431 + 0.005", so according to your measurement the hole and VIS are about 0.004" farther apart than allowed by the spec.

No wonder the barrel makes no VIS contact! The frame's way, way out of spec!

Quote:
I'm gonna be really upset if it turns out that the frame is no good. I waited 8 (censored) weeks for it, and paid $50 for the transfer.

After you recheck your measurements (and settle down a bit) I'd recommend a call to Caspian explaining the problem and what you've found on their receiver.

My condolences.

P.S.: FWIW, the spec for that last measurement is shown as 0.431 + 0.005" on the US Army blueprint in our Technical Issues section. J.K. says it's 0.431 +/- 0.005, huh? Hmmm. Think I'll stick the Army one.


niemi24s
6th October 2008

And, FWIW, according to your measurements the distance from the center of the SS pin hole to the "corner" of the VIS & bed is 0.0087" more than allowed by the extremes of the specifications!!

Cheers - if you can find some.

P.S.: I'd also be suspicious of the proper location of all the other frame holes as the SS pin hole is the reference point for locating almost all of them. And, if the SS pin holes located wrong, it could be that the other holes are also in the wrong position on the frame. Maybe.

And, when you call Caspian, make sure they know you made the measurements with a Mitutoyo caliper - and not some $12 piece of junk from Big Lots or Harbor Freight. Mitutoyo makes good stuff!


Suburban
6th October 2008

I tried using Allen keys as pin gages.

SS pin hole to VIS is RIGHT AT maximum spec, 0.436". I must have been measuring at at angle or something. Slide stop hole depth (from top of rails) is somewhere within spec., but on the deep side using the Allen keys as go no- go gages.

Yeah, it is a quality caliper. Something like $250 retail price, but fortunately, I got it from work.

I haven't gotten so far as to fit the slide to frame yet. This may have a little to do with the slide stop hole seeming to be too low.

So, assuming the remaining dimension is actually within spec. I'd need a longer link, which means no lower lug support at linkup, and trimming the chamber end of the barrel to get the 1/32" gap? Not exactly an optimum solution.


Hawkmoon
6th October 2008

How does the gap look if you drop the barrel into the frame with VIS contact and no slide stop installed? Is there any gap at all? If so, try it like that and see if/how it works. But, yes, it appears that you need a longer link to allow lug-to-VIS contact.


niemi24s
6th October 2008

I just checked the only Caspian frame I have and the VIS to center of SS is .4400", a Colt Gold Cup was .4405" and an STI is .4450" so I say there's a lot a hope to be had. It's just which direction to go and not screw it up that.

FWIW, my old WWII-vintage Remington Rand (maybe US&S) measures about 0.441" after Lord-only-knows how many rounds.

Even with a pretty snug-fitting #5 drill in the hole, this is still a pretty iffy measurement with the ID nibs of a Mitutoyo vernier caliper. Ah, my kingdom for a height gauge!

If you're thinking about some bed lowering, I'll see if I can figure out how much lowering would be needed. That's the only solution (other than another frame) I can think of at present.

If we just knew how far the lugs were from the VIS I think that would help. Maybe I'll try it with some Plasti-Gage in the morning to see if that method will work.


niemi24s
6th October 2008

Howzabout this as a first step?

PICTURE 404

If the elongation to obtain VIS contact delays slide/barrel lug disengagement too much, then maybe think about lowering the bed (or calling Caspian)?


log man
6th October 2008

Elongating the slide stop pin hole is discouraged by some, but it is definitely on the list of possible alterations. The question that needs to be answered first however, is the one I've been asking and that is the top of barrel to inside of slide at link down clearance. If it isn't at least .010" and that's minimum then the bed needs to go down anyway. Elongating the link will perhaps allow VIS contact, but will do nothing for clearance.


Suburban
7th October 2008

Quote:
How does the gap look if you drop the barrel into the frame with VIS contact and no slide stop installed? Is there any gap at all? If so, try it like that and see if/how it works. But, yes, it appears that you need a longer link to allow lug-to-VIS contact.

Just a tiny bit of a gap. Even less than the gap in the first picture on this page.

Oh, and BTW, thanks very much to everyone taking apart pistols to measure, and pitching in to help. It is much appreciated.


Hawkmoon
7th October 2008

Tuner has, in the past, suggested elongating the hole in the link. Log Man has a point, though -- if it results in insufficient link-down, it's a non- starter as a solution. I'd try it, though. Links are cheap (compared to frames and barrels).

What about going the other way? Use a longer link, and remove material from the web between the holes to allow the lugs to rest on the SS pin in battery. I suppose the end result is the same -- it's just somehow easier for me to visualize it that way.


niemi24s
7th October 2008

Quote:
I tried using Allen keys as pin gages.

Their hexagonal shape puts any measurement made using them in the realm of "guessing". You need something round - so it at least bottoms out in the hole. Dig up a few drills with shanks that aren't chewed up. The SS pin hole spec is 0.201 to 0.203", so (as drills are seldom precisely at their nominal diameter) a #5, #6, 13/64" or #7 should provide a reasonably snug fit. Pin gauges would be even better, if you can lay your hands on some.

Whatever you do, don't call Caspian with measurements taken using Allen keys!

If you can't find something round that's reasonably snug in the hole to use as a measurement reference surface, calculate the distances using the sloppy fitting round thing from:

[distance to center] = [measured distance to round thing] + [O.D. of round thing] - [1/2 x SS pin hole diameter]

This is with the round thing located in the SS pin hole to yield the maximum measured distance to it.

Quote:
I haven't gotten so far as to fit the slide to frame yet.

By this, do you mean the slide can't yet be installed onto the frame?

If so, one key measurement (clearance between barrel top and underside of slide) can't be done.

If, however, the slide WILL go on the frame - get that clearance/gap measurement. Assemble the frame, slide, barrel, bushing, link and SS. Pull the slide aft about 1/4" from battery and measure the gap with barrel down on the bed.


niemi24s
7th October 2008

Quote:
What about going the other way? Use a longer link, and remove material from the web between the holes to allow the lugs to rest on the SS pin in battery.

What a splendid idea!

This would not reduce the strength of the link when it's in tension - especially if more than just a few thousandths of material had to be removed.

IIRC, 1911 Tuner limits his link-lengthening to 0.003" but I don't recall whether his limit was based on timing concerns or link strength concerns.


niemi24s
7th October 2008

If you really don't have anything but hex keys to use to put in the hole, here's how to get the distances (if you haven't done this already):

PICTURE 404

Even a slide stop pin is better than a hex key!


niemi24s
8th October 2008

Hope I didn't give anybody a case of "algebra heebie-jeebies" with that last post, but here's some more info. Based on Suburban's latest measurements (and assuming the barrel is mid-spec), either:

* the supplied standard 278 link would need its hole(s) elongated a total of 0.013", or

* the bed would need to be lowered 0.015" to a distance of 0.090" below the frame top...

...in order to just barely obtain simultaneous VIS/bed contact at linkdown.

Of course, both the link and the bed could be modified to get VIS contact.

All this, however, is based on measurements taken using an allen key in the SS hole as a measurement reference!

IMHO, Suburban needs to either get some trustworthy measurements on this frame or get a new frame.


niemi24s
8th October 2008

And here's a pic of what the situation is - based on what I know:

PICTURE 404

A standard 278 link will only allow the hole centers to get 0.283" apart. If Suburban's barrel is mid-spec, the holes will be 0.295" apart when on the VIS and bed. 0.295 - 0.283 = 0.012", so a +13 link would be needed.

And, with a standard 278 link installed, the lower lug-VIS gap will be a tad less than 0.020" if the link, pins, holes and barrel are all at their mid-spec values.

[I just woke up in a calculating mood this morning. Don't fret, it'll soon pass!]


Suburban
9th October 2008

Quote:
If you can't find something round that's reasonably snug in the hole to use as a measurement reference surface, calculate the distances using the sloppy fitting round thing from:

[distance to center] = [measured distance to round thing] + [O.D. of round thing] - [1/2 x SS pin hole diameter]

That's what I did. I wrote something about compensating for the slide stop pin being undersized. That was it. I did a lot of QA stuff a few years ago. The calipers and micrometer, and some little stuff stayed in my toolbox, but I can't borrow the pin set or a depth mic.

The Allen keys were measured with a micrometer. Perhaps not the best solution to the problem, but it was enough to pacify my concerns of the frame being out of spec in terms of the SS pin hole to the VIS, and SS pin hole depth. I never put an Allen key in the SS hole. Maybe I phased the post poorly.

I did, eventually, dig up some drill bits the right diameter to gage the barrel bed height.

I'm not really sure why my measurements with the ID points, and depth measurement slide were so far off, but I'm sure they were off, now.

Quote:
By this, do you mean the slide can't yet be installed onto the frame?

Yup. I'm going for a "hard fit" between the slide and frame. I've got the rear of the slide about to where the front of the mag lips would be. Got a ways to go yet, and I don't want to rush the job. I was warned that it could take as long as 8 hours, and that seems about right.

Hmm, maybe that's what I should have engraved on the blank side of the slide. "Done Right The First Time."

As soon as I can get it to go all the way back, I'll measure the clearance between slide and barrel. I posted in the Caspian folder of that other 1911 forum, and it's sounding like lowering the bed is pretty common.

I like the idea of installing the longer link and filing it to give lower lug support. If the barrel bed turns out to be okay, I could live with that solution. I can't come up with a downside... other than having to knock loose the tightly fitted link pin and more tedious file work. I'd be a little more concerned about trying to make the current link fit. I'd be afraid that it might break.

I'll burn that bridge when I come to it.


niemi24s
9th October 2008

Quote:
I wrote something about compensating for the slide stop pin being undersized.slide.

Indeed you did, and it didn't sink far enough into my brain!

Anyway, are your most recent measurements the same as those in my last post (the three "M=___" ones)?


Suburban
9th October 2008

Anyway, are your most recent measurements the same as those in my last post (the three "M=___" ones)?

I'm pretty sure the frame is within spec, beyond that, I can't really say.


niemi24s
10th October 2008

Quote:
I'm pretty sure the frame is within spec, beyond that, I can't really say.

I take it from this that you're pretty sure the center of the SS pin hole is no farther than 0.450" from the frame's top?

If it is indeed no farther than 0.450", then I think you can make it work with maybe a little link and/or bed work.

However if it's 0.461" as previously reported, this 0.011" beyond spec limit coupled with the distance to the VIS being right at the upper spec limit will combine to make it a real chore to get the assembled gun to work.

But, from what I've heard, Caspian makes good stuff and Kart barrels are top- notch products. I'll keep my fingers crossed for ya!


Suburban
25th October 2008

I got the slide on, and moving freely. The .01" feeler gage would not fit between the slide and the top of the barrel.

After sanding down the barrel bed to the point that the gage goes in without shoving, the lower lug is now contacting the impact surface.

The gap between the top edge of the frame ramp and the barrel is still very small, but I'm not going to mess with that until I get to put some rounds through the assembled pistol.


log man
25th October 2008

This was my suspicion and am glad you went through with the fitting procedure. This condition that you encountered is not unusual when fitting a new barrel to a new frame and slide. Now that you have an understanding of the mechanics of barrel link down you can see that to get more barrel to slide clearance you would need to move the VIS back and the bed down. This fitting process doesn't suggest that there was anything actually wrong or out of spec. in regards to the frame.


niemi24s
26th October 2008

Quote:
This fitting process doesn't suggest that there was anything actually wrong or out of spec. in regards to the frame.

If the fitting process you're referring to is the one detailed on the Schuemann Barrels website, I personally have my own doubts about it.

If you follow those instructions on a mid-spec U.S.G.I. M1911A1, you'll end up lowering the bed 0.025" and moving the VIS back 0.010".

Could JMB have got it that wrong? Or, could...


log man
26th October 2008

Oh, oh, why would you need to lower the bed which is basically parallel to the inside of the slide .025" when the most barrel to slide clearance one needs is .015"? While I agree that "mid-spec U.S.G.I. M1911A1" specifications are a good reference, I doubt companies like STI, SVI, Schuemann and Caspian are trying to be recognized as a mid-spec company. JMB got it exactly right for an in the dirt 8"-10" group, good enough to kill the enemy, at 50 yards dependable fighting pistol. As that is also the specs for a "mid-spec U.S.G.I. M1911A1", and that isn't the goal today is it? Or is this the "Mid-spec U.S.G.I. M1911A1 Restoration" forum? I believe the OP is hoping for a better than "mid-spec U.S.G.I. M1911A1" accuracy, and other than mid-spec fitting is required for that.


niemi24s
26th October 2008

Quote:
Oh, oh, why would you need to lower the bed which is basically parallel to the inside of the slide .025" when the most barrel to slide clearance one needs is .015"?

Here's how (Referenced to Schuemann Test No. & paragraph No.):

* Test 1, Para 1 & 2: With no link, barrel on bed the gun'll have 0.00825" gap twixt barrel top and slide. Test says get 0.020" by lowering bed, so bed gets lowered 0.020 - 0.00825 = 0.01175".
* Test 1, Para 3, etc.: With barrel linked, fully aft and up (link in tension, lower lugs against VIS) the gun'll have a 0.00605" gap twixt barrel top and slide. Test says get 0.015" by moving the VIS back. To lower the barrel 0.015 - 0.00605 = 0.00895", the VIS must be moved back 0.01017"
* Test 2: [Does not apply as VIS was too far forward.]
* Test 3: With barrel linked, fully aft and down, there must be 0.005" between the bottom of the barrel and the bed (and inside of slide). Assuming slide clearance is adequate, the barrel will be on the bed with the link loose.

To get the link in compression holding the barrel 0.005" off the bed, the Test says to lower the bed. To get the loose link just into compression (barrel still on bed) the bed needs to be lowered 0.00884". Then it needs to be lowered another 0.005" to get the required barrel-to-bed gap for a total bed lowering in Test 3 of 0.00884 + 0.005 = 0.01384".

The bed got lowered 0.01175" to get Test 1 passed and another 0.01384" to get Test 3 passed and 0.01175 + 0.01384 = 0.02559" (0.025 to 0.026") of total lowering.

That's how.

Quote:
While I agree that "mid-spec U.S.G.I. M1911A1" specifications are a good reference...

They're not just a good reference - they're our only reference! None of us will probably ever have access to the dimensions and tolerances used by any of the current 1911 makers. Without those Army blueprints if somebody asked "how long's my disconnector supposed to be", we'd all measure ours and reply with a bunch of different lengths which really wouldn't answer the question.

Quote:
I believe the OP is hoping for a better than "mid-spec U.S.G.I. M1911A1" accuracy, and other than mid-spec fitting is required for that.

And a big +1.3867 to that!


log man
27th October 2008

Okay, that's interesting to know that a "mid-spec U.S.G.I. M1911A1" starts life with .00825" (how do you measure to the 100 thousandths?) between barrel and slide without the slide stop pin. Anyway after you figured you needed to take off another .025"-.026" from the bed you now have .03325"-.03425" between the barrel and slide without the slide stop pin installed. Seems excessive to me. How's it run?

Niemi, your understanding of test #3 is a little off as Wil doesn't say that the .005" under the barrel should be present with the barrel back and down under compression. He simply says that if you have .015" with the barrel forced up and back and you pull the slide stop pin and push the barrel down you should have an additional .005" which is part of the original .020". The insert directions that come with his barrels have the same information, however in it the dimensions are .015" and .010". His barrels are used mostly by USPSA shooters who as you may know shoot very rapidly and have very high round counts, and has seen barrel lugs ripped off of barrels and slides and has given us an understanding of how to avoid that.

Wil Schuemann is a very interesting guy to talk to and quite accessible. I've spoken to him a number of times and it's never been less then an hour. Give him a call about your concerns, Wil Schuemann's cell number is (541) 490-2993.

I for one believe Suburban is on the right track. He now has a minimum of .010" clearance and the lower lug is hitting the VIS, a little more would be better, but not a bad start, don't you think?


niemi24s
27th October 2008

These are results of calculations using values of the blueprint dimensions in the center of their tolerance bands. I customarily use 4 or 5 places past the decimal point to avoid loosing too much by rounding during the sequence of calculations. When done, the result's usually rounded to 3 or 4 places past the decimal point - usually 4 places if less than 1 inch, which most can measure.

Quote:
Anyway after you figured you needed to take off another .025"-.026" from the bed you now have .03325"-.03425" between the barrel and slide without the slide stop pin installed. Seems excessive to me.

Seems excessive to me too, but that's what you'll end up with after following Schuemann's procedures.

The disturbing part to me is after all this is done to a gun (a GI rattle- trap) that's as within the specifications as it can be (all parts half way between the max. and min. limits) you end up with a frame with:

* a bed level out of spec by 0.023" and
* a VIS out of spec by almost 0.007"

And nothing has been done to the barrel itself to get the gun to pass the tests!

Quote:
How's it run?

Run? It doesn't!

This is the result of a "what if" exercise on a hypothetical "blueprint gun".

Quote:
Wil Schuemann is a very interesting guy to talk to and quite accessible... Give him a call about your concerns

Did so about a year ago, sending him a copy of the calculations and drawings upon his request. No reply yet.

Quote:
I for one believe Suburban is on the right track. He now has a minimum of .010" clearance and the lower lug is hitting the VIS, a little more would be better, but not a bad start, don't you think?

Yeah, he'll get it going with help from folks like you - expecially if I quit all this hypothetical, theoretical 6 digit clap-trap cluttering up his thread!


log man
27th October 2008

Niemi, you might re-read my post in the middle, I added what I believe is the reason the numbers got so high, apparently while you where posting and probably missed it.

To add remember the link can not be truly in compression on a barrel whose feet have been fitted to ride the slide stop pin. With the correct link the pin will only contact the lug surface and the link will only touch the pin itself during the unlocking phase and will be in extension. On barrels that Bar-Sto provides a link the upper portion of the link pin hole is milled out so as to make sure it doesn't ride the pin and if the link isn't riding the pin it can't be in compression.


niemi24s
27th October 2008

Quote:
Niemi, your understanding of test #3 is a little off as Wil doesn't say that the .005" under the barrel should be present with the barrel back and down under compression.

Hmm-m-m. Could be the instructions he sends with his barrels differs from the one on his website, but current one there says:

"If the gun passes this test [barrel drops at least 0.005" when SS removed] there is a minimum of 0.005 inch between the bottom of the barrel and, in it's fully linked down position, and the top of the frame and the inside of the slide."

If the barrel drops 0.005" to the bed when the SS is removed (relieving link compression) it seems to me that when the SS is re-installed (re-establishing link compression) there must be a gap of 0.005" between the barrel and the bed.

After lowering the bed and moving the VIS back to get the gun to pass Test 1, its barrel will be on the bed and the 278 link will be loose when the SS is installed and barrel linked down. Because of this, the barrel cannot go down further when the SS is removed in Test 3. The gun does not pass Test 3.

In order to get the gun to pass Test 3, material is removed from the interfering surface - barrel bed in this case- until the barrel drops 0.005" when the SS is removed. That's why the additional 0.013 or so of bed lowering is required.

And I didn't see any mention anywhere in the timing tests about checking or changing the link length - so I just kept the standard 278 link through it all.

Quote:
He simply says that if you have .015" with the barrel forced up and back...

The website copy states in the first line of Test 3 "Assemble the 1911 without the recoil spring parts, without the test spring kit..." (italics mine) and the test spring kit is what's used to force the barrel up and back. With the barrel forced up and back putting the link in tension, the 0.010" of total play in the link system will allow the barrel to drop down 0.005" even when the up & back force is removed from the barrel and the SS is left installed!

Maybe the fitting directions that come with one of his barrels are different than the "Timing Test Kit" info on his website. If so, and those with the barrel are the proper ones, the website version should be corrected or deleted.

Tell ya what: why not let's continue this (if desired) by PM to avoid hijacking any more of Suburban's thread. I'll send you the stuff I sent Schuemann if you'll PM me your mailing address. OK?


log man
27th October 2008

That would be fine (PM), however the topic certainly is germane to Suburban and others interested in the topic. I do, Niemi, understand your numbers , but see them as the most extreme in the what if negative direction, Wil is also extreme as he has been held responsible for sheared upper and lower lugs and has given specifications to protect himself (there's an an acronym that fits but could cause trouble). I, as you should realize, did not bring up Wil Schuemann's specs. in regard to Suburban as I don't insist on the full .015", but do .010" and have gotten the .015" on some. The point also of course is that there is clearance under the barrel when it hit's the VIS and is imperative or pressure on the lower lug and link will ensue. No one's absolutely right or wrong on the topic as long as the result functions well without damage to any of the parts. I learned some time ago there's more than one way to do things right.


niemi24s
27th October 2008

Quote:
I do, Niemi, understand your numbers , but see them as the most extreme in the what if negative direction...

All I did was apply the tests to an average (mid-spec) GI 1911 to see whether or not it would pass the tests in the instructions and, if not, take the corrective actions in the instruction.

And no, they're not the most extreme.

With a judicious selection of specs at either the upper or lower limit for each, I could concoct an in-spec gun needing even more bed lowering and more VIS moving back - making it extremer (!) than the mid-spec gun.

But that's an exercise for a snowy/rainy day when there's absitively, posolutely nothing else to do!!


niemi24s
4th November 2008

Quote:
Maybe the fitting directions that come with one of his barrels are different than the "Timing Test Kit" info on his website.

And indeed they are, thanks to Log Man sending me a copy.

Without one of his barrels or knowing for sure what their specs are, a paperwork exercise was done using a USGI barrel with the hood and lugs welded up (like in the olden days) following the Schuemann barrel fitting instructions. After fitting the hood, a synopsis of actions taken in following the rest of those instructions is:

* Lugs cut for maximum vertical engagement of 0.0595" on Lug #1
* Lower standing lugs measured and led to installation of a +17 link
* +17 link would not allow vertical disengagement before VIS contact
* VIS moved back 0.0190" to barely allow vertical disengagement
* VIS moved back another 0.0106" to obtain barrel/slide gap of 0.010"
* Barrel bed lowered 0.002" in conjunction with previous step to avoid first contact with the bed (and actually get the 0.010" gap).

After all this, the VIS-to-SS pin hole center distance was about 0.027" more than the max spec, but the bed-to-SS pin hole center distance remained within spec (barely).

The lug cutting part of the exercise was done with the barrel forced up into the slide, but the slide was not forced up on the frame. For an average GI gun, the 0.004" of vertical slop between slide and frame would result in the use of a +21 link and the VIS getting moved back about 0.004" more.

I've had enough of these hypothetical, mathematical barrel fitting shenanigans - have you?


log man
4th November 2008

Niemi,Another thing that would help in understanding the differences between a USGI barrel and the ones Wil Schuemann thinks are being used is the position of the upper barrel lugs. In a USGI barrel the lug slots are cut to a nominal .290". Schuemann barrels are cut to .297" in slots 2&3 and #1 slot is cut to .302", this difference allows the barrel to engage the slide with less upper movement and is the reason for it. A #4 (.283") or at most a #5 (.288") link is all it takes in an actual gun.


niemi24s
4th November 2008

Do his barrels have about the same lug heights as a GI barrel (about 0.059")?


log man
5th November 2008

Do his barrels have about the same lug heights as a GI barrel (about 0.059")?

No, Niemi they aren't as the lug recess depth is less due to the difference of the lug cut from the USGI .290" to the N.M. std. of .302". Most match grade barrels, Bar-Sto, Kart, Schuemann and others will measure in the first lug recess .045".


niemi24s
5th November 2008

Quote:
Most match grade barrels, Bar-Sto, Kart, Schuemann and others will measure in the first lug recess .045".

Well, that explains it all!

With about 0.015" less barrel lug height, the barrel will go that much less up into the slide, the barrel link pin hole will be about that much closer to the SS pin after the lugs are cut and the link can therefore be about 0.015" shorter. On paper, this barrel will disengage with a +3 link leaving a 0.002" gap and the VIS only needs 0.011" of trimming to get the 0.010" gap.


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