fitting 1911 barrel

[1911Tuner]

Locked up

Hey Mike,

You can expect slide advace on the frame about a 3:1 ratio if you cut the lug further back. Not sure of the exact formula for calculating it, but that's about the amount I've noticed in some few that I've adjusted the lug to delay unlock...none of which were for accuracy, but to stop tadpole-tails on the primers and gas in the face.

Your barrel drops .001 inch at .070 inch of travel...without the link. Adding the link to the mix may give a different result, just like not using pressure on the hood. Also...don't forget that when the barrel is under pressure, it's not gonna drop from the slide under gravity alone. It has to back off the pin
far enough that the link can exert its influence without the lug solidly on top of the pin. The more slope on the lug...the earlier...and the more...it drops.

All this may be for naught, though. Looks like you may wind up with another barrel anyway if you can't get the gun to shoot like you want by massaging this barrel.

 

[1911Tuner]

More Stuff from Fuff

True enough...but reducing the amount of slope on the lower lug would
limit the barrel movement past the point of starting to unlock, and maybe serve to make it a little more stable. Like I said...Might work and might not.
Worth a try, since he's pretty much figgerin' on barrel work anyway.

The firing pin stop's influence can be offset softball with a 2-pound drop in recoil spring load if need be...but it may not. I've got a pair of early 1991A1s
that have a 23-pound mainspring...a 16-pound recoil spring...and the small-radiused stop. Just for he helluvit, I shot some of Kelie's Softball ammo in'em...185-grain lead bullets loaded to 700 fps...and the guns cycled well enough to lock the slides 7 times in 10. I could clip one coil off the recoil springs and they'd run, even though the brass falls on my right foot.

 

[mikejm]

At times i can be a real dumb bunny ( maybe easter has something to do with it ), but i do not understand old fuff stating that not cutting more is better?
ok,the first barrel they put in wasn't cut enough, the slide was not even with the frame by at least .040 , so when the slide comes back the .080 or so in recoil the slide was already back by .o40 and it only had to come back another.040 when it started to unlock...... all my cases were black, because the slide/barrel was unlocking while the pressure was way up at the beginning of the internal ballistic... having said that with this 2nd barrel that was installed the cut on the lugs is likely approximate in the positioning but only marginally so....because the barrel is really starting to unlock about .070 an isn't that early? if i extended the cut another .010 or even .030 more, wouldn't i get into the better zone where the slide is still in lock before the bullet exits the barrel?
where and what am i missing if that's not correct ?
trying to comprendo
mike

 

[Old Fuff]

Tuner:

I believe he has a slide with a heavy Bomar rib. In that case the slide will almost run on momentum alone. They were designed and intended to work with very mild pussycat loads. I am sure the extra-heavy slide will have some effect on the cycling rate. It should be slower to start, but then it will go like gangbusters if the recoil spring is too light for the cartridge's load.

Mike:

It depends on where you're removing metal. If it is on the bottom lug in front of the slide stop pin the barrel will drop down sooner as the link pivots the barrel downward and backwards. That is, if the link will let it do so.

 

[Old Fuff]

Mike:

Another thought has come to me. If you have a set of twist drills find one that will just go through the slide stop hole in the link and then mike the diameter. Could be that the link is part of the problem.

 

[1911Tuner]

Bomar Rib

I see...I see...Okay! Nix the lighter recoil spring then. The FP stop still might be workable, though.

Same ol' same...Change one thing, and ya might as well get ready to change 3 or 4. :banghead:

Fuff, Mike was thinkin' about a cut on the lug that would set the pin deeper.
I suggested makin' the bottom part of the lug flatter to keep the barrel closer to the same place longer in hopes that it might limit the arc as it drops..even though it would still start a little early, it would remain at THAT point over a longer time frame. Might help...Might not.

 

[mikejm]

darn , On to test #2 with link installed, i believe it is .010 longer than standard
I make mistake on setting up the up/down indicator, so here goes again
the indicator stays at zero untils there is .110 of slide movement where it drops only .0005, then at .115 it practically drops like a rock almost immediately....looks like the barrel is riding the link. right , no? not good huh?
I made a pin that just barely fits the slide lock pin hole a very tight fit , measures .201 , the slide lock pin that i use now measures .1995 , i used this pin for the test and for what it's worth , i just replaced the recoil spring with a new Wolff 14#
thanks
mike

 

[Old Fuff]

The light is starting to dawn ...

Put some layout dye on the bottom of the lug, reassemble the pistol, hand cycle it, and then look at the bottom of the lug to see if the slide stop pin is rubbing, and where.

If the link is long, and the hole isn't oversized, it is probable the link, and not the lug is what's locking the barrel as the slide goes into battery. You should have one or the other, but not both together.

My USGI blueprint for a link modified to be used when the barrel is cammed by the slide stop pin has the hole dimensioned at .230 +/- .001 Center-to-center dimension between the holes at .291 +/- .001

Are you saying the hole in the frame, or the hole in the link is .201"?

 

[1911Tuner]

Light at the end of the Tunnel!

Yep...Sounds like you might have a "rider". A quick-check is to just look at the slidestop pin to see where the the rub mark is. If it's the same width as the link...and on the top of the pin...it's a-ridin' it.

To verify...Ease the slide into battery and measure the distance from the top of the slide to the top of the hood with and without the link. If it locks higher with the link...it's a-ridin' it.

 

[mikejm]

tuner, that's exactly what i thought on the last test, that the barrel is riding the link and not the pin
old fuff
the hole in the frame is .2035
hole in link vertically is .2045
hole in link horizontally .203
with just barrel and link in hand i can rotate the slide lock pin around the corner so to speak with the link installed on the barrel
slide pin .1995
with the pistol assembled including link , i can just barely fit a .201 pin where the slide lock pin fits.... i'll try the dye test later.What part and why is it not good for the barrel to ride the link? like, what happens?
thanks mucho gentlemen

mike

 

[mikejm]

Applied layout dye on the barrel lugs and the slide lock pin. After cycling the slide several times, there are two bright spots on the top of the pin that interfaces with the lugs , there are bright spots along the contact area on the lugs where the pin slides along full length as well. There is not rub marks on the pin where the link would interface.

I measured the slide lockup height with the link installed and removed , the measurements were identical

mike

 

[Old Fuff]

This is going to take some thought ... and by now Tuner has gone to bed.

Be that as it may. When a barrel is cammed into battery by the slide stop pin pressing on the lower barrel lug the link is supposed to have an oversized hole in it, and thereafter only drops the barrel to unlock it and nothing else. I would expect the link in your barrel to have a .230" hole for the slide stop pin, which is about .200 Since the pin is acting to cam the barrel the hole location and size in the frame and link, and the diameter of the slidestop pin must be held to the closest possible tolerances. The hole in the link can be, and should be about .030 oversized. It would appear that in your case it isn't. But maybe the cam surface in the lug is so close it doesn't mtter because there is enough tolerance stack to allow the barrel to ride on the slide stop pin, and the tight link doesn't matter. If so, this is a first for me.

If the pistol was laying on my workbench, or on Tuners, we could make some solid judgments in short order. As it is we have to give out a lot of speculation.

Another test. Insert the slide stop through the link and frame, and then lower the slide into batttery while the slide stop lever is pointed down rather then in place. See if you can pivot the slide stop. If the barrel lug is pressing on the slide stop pin there should be resistance. If there is, see how far you have to push the slide/barrel backwards before the pressure on the slide stop pin goes away, or if it does at all. What I'm looking for is evidence of binding.

Now it's past my bedtime so I'll have to get back to you tomorrow,

 

[mikejm]

old fuff ..... Here's a good morning question for you, with the pistol assembled and the slide stop pin hanging, do you mean to push down on the barrel while closing the slide to lockup? should the recoil spring be in ? i guess i may not fully understand the test , can you try explaining again
thanks and later
mike

 

[Old Fuff]

Good morning to you too. The sun is out in Arizona, and a high of 66 is predicted.

What am I doing? Not sure, but at this point Tuner and I are playing hunches. It would seem that your barrel is being locked into battery by both the link and the camming action of the lower barrel lug bearing on the slide stop pin. If so this shouldn’t be, and in fact something should be binding, although so far I don’t see evidence of that.

So long as the pistol can be pushed into battery you don’t need the recoil spring, but of course you do need the barrel bushing. You also don’t need to push down on the barrel at the hood, because it seems that either the lug/slide stop pin or link (or both) are pushing the barrel upwards into a firm lock-up. If the link is removed you probably will have to push the barrel down to get it to unlock at the start of the cycle. What I am looking for is if the slide stop won’t pivot if when the barrel is in battery – indicating that pressure from either the lug or the link is causing a bind. I would expect that if the barrel was cammed into battery by the lug/slide stop, and that could be determined by removing the link and repeating the test to see if there was more or less pressure on the slide stop pin. If the barrel is standing on the link I would expect it would take some pressure to push the slide into battery, and a slide stop that didn’t want to rotate – unless the link fit was absolutely perfect.

An old pistolsmith’s trick is to assemble everything (and/or with or without the link) and hand-cycle the slide without the recoil spring in place. This way you can literally feel what is happening as the slide moves back and forth and the barrel unlocks and locks. Of course if the link has been removed you may have to press down on the hood with your finger or thumb to get it started in the unlocking phase as the slide starts back.

I think Tuner is looking at two things. First, the way the slide starts to move back while the barrel starts to unlock, and then suddenly “drops like a rock.†This was something that was unexpected. The second thing is that the hole in the link is a close sliding fit on the slide stop pin, where we would expect a hole to be about .030†larger then the pin. This clearance is to insure that the link does not interfere with the slide stop/barrel lug’s camming action.

As I said before, if the pistol was laying on one of our workbenches we would hopefully conclude something before long. As it is we have to speculate.

If you have not already done so, you should purchase a copy of Jerry Kuhnhausen’s excellent little book, “The Colt .45 Automatic – A Shop Manual (Books 1 & 2)†– both books are in one volume, and Book 2 details how to hand fit a match barrel.

 

[mikejm]

ahhhh another new day , hope everyone has a good one !
back to the vise , link out , pin in ... at lock ,pin is tite, back the slide out .020, pin is very loose and the barrel is already dropping 2 - 3 thou.the numbers here are not the same as my first test , but there must have been some crud holding it up, but now it definately drops very fast as the slide is moved back without the link
link in , pin is tite , move slide back, pin will actually start to rotate and will stay tite until about .090 then gets loose and another few thou. back the barrel drops fast, but stays almost zero until then.Almost identical to test 2
this slide has been lowered a lot to get a tite fit, i'm sure this has an effect on the link geometry, just my thought... another thought ( dangerous)
is in the link pin hole in the link, isn't this hole supposed to be pin size ? enlarging the hole at the outer will have an adverse affect on the timing ?
do you mean it should be .203 or .230
mike

 

[Old Fuff]

In a regular 1911 pistol both holes in the link should be a slip fit on the respective pins that go through those holes. This is because the link both lowers the barrel when the slide is retracted, and pushes it up into the locked position when the slide is in battery. This usually leaves the barrel floating a little bit when the slide is in battery, but it is acceptable, and even desirable in a service pistol - which the 1911 was originally intended to be.

Bullseye target shooters however don't want any float, they was the barrel locked firmly with no movement to they'll get maximum accuracy.

During the late 1950's some custom 'smiths and armorers at Springfield Armory discovered that if enough material was on the barrel's lower lug, or the lug was built up with welding, it could be "adjusted" so that the lug pressing on the slide stop pin would cam the barrel into the locked position, and unlike the link would allow each barrel to be individually fitted to a particular pistol in a manner (if done right) would lock the barrel into a position where there was no possibility of movement each time the slide returred to battery. Of course fitting the hood and barrel/bushing fit played a part, but we can ignore that for the moment. However if the barrel was set up so that the slide stop/barrel lug camming system was used it was necessary to enlarge the hole in the link so that the link would only pull the barrel down to unlock and otherwise have no function.

When the camming system is used (as it usually is a all match target guns) the only modification to the link is to open the lower (slide stop pin) hole from .2045 +.001 to .230 +.001 In both cases the upper (link pin) hole remains at .1565 +001

The slide stop pin diameter should be .2003 - .2005 The slide stop hole in the frame should be .201 - .203 Hopefully it will be on the low side, but this is not necessary.

It appears that the link in your barrel is designed to both lock and unlock the barrel, and this is not what you are supposed to have. If the link is the one that came with the barrel it might be a good idea to call Bar-Sto and ask. Maybe your barrel wasn't intended to be fitted using the slide stop/barrel lug camming method. If it was you have the wrong kind of link.

 

[mikejm]

repeated the first test with a little help with my thumb on the bbl.
Link was left out. by .070 the bbl. dropped .001, at ..085 it's .002 , at .095 its .004 , at .100 it's .005 and drops pretty fast from there.

the smith had likely used a std fit barrel , i can see weld pits in the lug and hood area , then they bead blasted to change the welded appearance. The link is longer than the original by .010 by comparison . I tried a shorter one and it wouldn't fit around the cam on the lug, so this one fits perfect to get around the cam , and to continue if this pistol is riding the link, then it too long right, but a shorter one won't fit.... so, my peanut brain says the only thing to do is keep the same link , but have the lug lowered a few thousandths by weld and recut the lug lower to free up the link? is that the solution? or, do what Giles did on his pistols, he soldered a shim in the lug recess on the slide , probably to center the FP and to get a favourable lug/link geometry?


gonna do a little ramblin, the browning design as described by fuff and tuner
point out that the barrel locks and unlocks by link alone. OK , to make it accurate you must get rid of the link arc and so smiths lower the lug and put in a shelf for the link pin to ride on within full lockup the entire way . Again as fuff says , the link is loose and the only function it serves is to pull the barrel out of lockup. Again ,OK, in my case it seems the link is long by likely a few thousandths, so why not cut the inside of the link hole a thousanths at a time until the lug is clearly running the shelf. Then tests with link in and link out should be identical......but somewhere i am led to understand that doing this is undesirable, and i don't know why.... it seems the present link is ok for timeing andpulling the barrel out of lock, so i don't see any gain to change that. Somthing else that I just remembered, the slide was tightened/squeezed quite a bit and you can see where the barrel has been rubbing the full length of the slide
mike