fitting 1911 barrel

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mikejm

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briefly , what is the fitting sequence of a barrel in a 1911, in terms of the upper, lower lugs , hood adjustments and link components? so the pistol will hold 2 in. or less at 50 yds.... also to consider headspace considerations
thanks
mike
 
I assume 2 inches with a Ransome rest-easier to achieve than with sand bags or off hand. I once saw a video of Jim Clark Jr. fitting a 1911 .38 Special barrel and then testing in a Ransome rest in a tunnel. I do not know if they sell the video.

I have only fit one barrel that will do 2 inches at 50 yards. It is a Kart NM "EZ" fit. It comes with 12 pages of small print instructions and some fitting componets. It took me 15+ hours to do it. None of the other pistols I have completed will do 2 inches at 50 yards so I am no expert. I have a Custom Open STI that will do 2 inches at 50 yards but I did not build it.

For that kind of accuracy I suggest you get information from some one who some experience building bullseye pistols reasonably frequently.

Also it takes a little time to learn how to use the Ransome rest and get repeatable results or at least it did me.

Dean
[email protected]
410-952-7848
 
Havin' Fits

Howdy Mike,

Whew! This one could get involved. There are several differnt views on the question of match-grade barrel fitting, and almost as many approaches.

The barrel is fitted in two planes...Vertical and horizontal. In the horizontal,
lockup is achieved with a tight fit between the front faces of the locking lugs
to the corresponding rear faces of the lugs in the slide. This is achieved by
using a long hood and adjusting it to fit into the slide with zero play so that the thrust faces are in contact with the pistol in battery.

Some smiths take the approach that only the first lug is necessary with a
.45 ACP caliber pistol because of the low pressure. Others want all lugs
bearing an equal part of the load. I like equal distribution over all three lugs if I can get it.

Then there's the vertical lockup...the amount of the total lug height that engages the slots in the slide...in an attempt to get as close to 100%
engagement as possible. This is usually doable on the first lug, but not quite so on the two forward lugs due to the tilting barrel. More clearance for the slide is available at the rear because it falls lower than the front lug...so a compromise is necessary.

The other factor is the centering of the barrel in the breechface, so that the firing pin will hit as close to dead center as can be managed. Lug heights on the barrel to slot depths in the slide need adjustment. Some smiths
don't place a great deal of importance on this factor....but I do. I've been known to weld a lug and refit it to gain an extra .003 inch. Extreme...and probably not necessary...but sometimes I like to see just how close I can get it. No time constraints are a good thing.

Basically, I like to start with a "Hard-Fit" barrel with long hood and short chamber and go from there. By gauging the distances from the breechface to the thrust faces of the slide lugs...and the distance from the hood face to the thrust faces of the slide lugs...I can adjust the faces of the barrel lugs themselves to get equal lug contact...or leave a tiny gap between the thrust
faces in order to let the lugs pressure equalize on firing. This requires cutting the chamber short and firing the gun to "Slap-Seat" the lugs. This gap must be very small...no more than about .001 or .002 inch...along with a fairly tight hood fit to allow the lugs to seat without losing the tight horizontal lockup provided by the hood. When they seat, the fit of the hood loosens up a bit due to the barrel shifting forward in the slide as the lugs set back to equalize. Then, the chamber is finish-reamed to depth. I like to set that depth at .003-inch to .005 inch over minumum as determined by using the SAAMI standard GO gauge. (.898 inch) My primary gauge is .895 inch.

At that point, the decision is made to either leave the hood with a zero-clearance linear fit in the slide, or file a couple of thousandths off to provide
a little dirt clearance...as the intended role of the pistol dictates. Target pistols don't get the clearance. Carry pistols do.

Then, there's the vertical lockup provided by fitting the lower lug to cam the
barrel up on the slidestop crosspin. You want zero vertical play at the rear of the barrel...but you don't want it to bind as it goes into battery. Again...
a purely target pistol gets a little tighter fit than a carry gun, but there is
very little difference here. I typically fit a carry gun as tight as a match gun
and finish-lap by hand with a length of .200 drill rod.

The sides of the hood are also a consideration. Target guns are held close to zero clearance there. Carry guns get a bit more. Ordnance-spec, or production guns are pretty loose here...as much as .010 inch per side. A fitted hood on a carry gun can do pretty well with a lot less, and still allow for dirt and carbon fouling. For a carry gun, I like to see about .003 inch
per side, but a little more is okay...up to about .005 inch. What you're after here is limiting the barrel's tendency to rotate...or torque...when the gun is fired. The fit of the sides of the lower barrel lug to the frame recess is also a limiting factor, but there has to be a little clearance there to allow the barrel to link down, so it can't be the limiting factor. The fit on the sides of the hood also aid in returning the barrel to the same position on every cycle.

The most important thing is that the barrel lock up well at the bushing...the hood...the bottom of the lower lug to slidestop pin, and equal support of the lower lug on the pin from side to side...and the barrel crown.

I think that too much is made of the slide to frame fit, side-to-side It plays a role in the overall picture, but only a small one. You want to hold it pretty close, but zero isn't really necessary and is a detriment to free slide movement. More important is the vertical...or up and down clearance between slide and frame. I can live with .005 inch of side-play as long as I can get nearly zero in the vertical plane.

Hope this helps...
 
Back during the 1960's the Army experimented at Springfield Armory while they were building USGI National Match pistols for various military shooting teams, and for use during the National Trophy Match (pistol) that was held each year at Camp Perry, Ohio. These pistols were in relative terms, mass produced and all were built on USGI 1911-A1 frames. The first "hard fit" barrels were designed and made for the National Match Program. Before this gunsmiths had to weld up the hoods and lower barrel lug and then fit the barrel to a particular gun.

At the time, the program was run by an engineer named Gene Taylor, who had forgot more about the 1911 then I'll ever know. Fortunately he was very generous when it came to handing out information.

They're accuracy standard was 5 shots off of a machine rest at 50 yards, with the bullets going into a group no larger then 3-inches measured center-to-center between the two most outside shots in the group. They used National Match grade hardball ammunition, which was required in the matches where the pistols would be used. This 3-inch standard was about the best the ammunition would do out of a bolt action barreled test fixture at the same distance. BTW, they tested all of the guns they made, not a selected sample.

At one time they built a series of pistols, where after each step in the accurizing process the pistol(s) were machine rest tested to see what affect each step had on the pistol's ultimate accuracy. Slide-to-frame fit only accounted for 3 percent of the total improvement. By far the most important factor was barrel-to-slide fit.

Consistent groups at 50 yards of 2-inches and under are very difficult to get because of limitations in the ammunition as well as the pistol. If and when this is done the pistol must have absolutely zero tolerances in the barrel's lockup when the gun is in battery. This may be fine in a pure match pistol, but it isn't anything I'd want in a weapon. In this case "zero tolerance" is an invite to malfunctioning as soon as the pistol gets fouled or lubrication displaced.

Two-inch groups at 25 yards are relatively easy to get, and a more realistic standard for anything except a bullseye match pistol.
 
Welded Barrels

Weldin'em up and cuttin'em back to fit...Ahhh! Those were the days! :rolleyes: Bad ol' days! Those "Hard-Fit" barrels are the nuts, and I understand...though I don't know...yet...that the Kart EZ-Fit system is
the double-nuts for the hobbyist.

Part two:

Bushing to slide and barrel to bushing fit is one critical area that needs to
be addressed a little further, lest the first-timer think that all he needs to do is make it good'n'tight. The barrel tilts...up into battery/lockup...and down
into unlock/linkdown. If the bushing to barrel fit causes the barrel to be forcibly locked in the vertical plane, it creates "Barrel Spring" and actually
bends the barrel in the middle. Not a good thing. The bushing needs to be clearanced a bit at the inside rear area...and sometimes a little at the front
bottom...to allow the barrel to vertically lock in the slide without requiring force.

Then, there's the matter of linkdown clearance. Most production, ordnance-spec pistols come with barrels that have a slight flare toward the muzzle end.
This allosw for a closer fit with the bushing, and still provide adequate clearance behind the flare for the barrel to unlock. This flare is sometimes
referred to as the "Fitting Pad." The diffrence in the two diameters typically runst to about .006 inch or so...and if your hard-fit barrel doesn't have it,
you'll have to put it there, or go with a bushingless system. This is accomplished with a barrel turning fixture and a lathe. It's also helpful to
scrape a little clearancing provision at the rear bottom edge of the bushing,
just for a little added insurance that the barrel will fall into bed.

And THEN there's the little matter of adjusting the barrel stop surface and
frame bridge so that the link won't be stressed and stretched by the barrel stopping on the bridge...and so that the barrel lugs won't be peened, rolled, or sheared by the slide if the barrel hits the stop surface before it's completely unlocked, AND THEN there's the matter of selecting the correct link to match the lower lug's dimensions and geometry...and it goes on and on....don't it? :p
 
woowee, lots of info here, love it, i'm off to the range ;-) but when i get back i will read all the replies, essentially i had a smith install a barsto and after taking it back twice , it is still loose and the gun wont shoot ( large groups with my best hand loads) , they had welded the hood and filed the lugs when they promised that they would use a lug cutter and didnt and the hood fit still rotates, so i propose to weld the hood and lower lugs and recut myself, but i must get all the operations in correct order , right?
gotta go
thanks for the help
mike
 
Tuner,

My vision of my fitting of a barrel in my 1911s is in 3 planes/dimensions with spiral rifling and torque issues whether I hard fit or use a Kart NM “EZ†fit barrel.(I can do both). I am however only an amateur "hobbyist" not a professional gunsmith/pistolsmith/armorer. Are only 2 planes important for 2 inches at 50 yards?

Dean
[email protected]
410-952-7848
 
Plane Geometry

Howdy dean,

Go back and read it again. I touched on the torque question in the part about hood width/side play in the slide's recess. I don't think of rotation due to torque as a plane. but rather a directional response to torque. (Length/Width/Depth...or XYZ axes.) Vertical...Horizontal...Side play

Cheers!
 
3rd Plane

Nah...That's included in the horizontal lockup. Barrel lug and hood face fit, etc.

Speakin' of fits...I'm havin' my third one today as we speak. I couldn't be an accountant without drinkin' more than what would be prudent... :cuss: :banghead:

I HATE paperwork!
 
the adjustments and fitting are for a bullseye match pistol , and as far as the barrel fit is concerned, the hood fit is touching the breech at the corners, the lower lugs lightly touch the slide pin, the bushing has almost zero play and is clearanced to allow unlocking and locking, the only area that i suspect is the upper lugs. I can slide a cig paper ( .001 ) out of the top lug without tearing. Now , if that's the case, the hood touches the breach , the lower lugs are a good fit , the bushing is tite, but the upper lugs are suspect . Is this not good? what should be the case and what should be done to make it right?
thanks for all the good stuff
mike
 
Mike:

If that Bar-Sto barrel has been welded, and especially if it has been welded more then once, I wouldn't continue to use it. It sounds to me like this sorry example of a gunsmith(?) doesn't know what he's doing, and by now the hood and lug areas may be imbrittled or excessively soft. Rather then take a chance I would purchase another barrel and have Bar-Sto fit it. They know what they're doing and they don't do it by welding.
 
Lug Clearance

Little confused here...If the clearance is between the top of the hood and the frame bridge...that's not the lug. The thrust face of the first slide lug is
under and slightly forward of the bridge, and the thrust face of the first barrel lug is at the front of the hood.

If there's clearance between the first thrust surfaces, the #1 lug isn't
bearing any of the load and is being held off by one or both of the two forward lugs. If this distance is very tiny...maybe .001 inch...the lugs may equalize in time, after firing it enough.

In agreement with Fuff, by the way. Unless the welder knew his stuff as to quenching and drawing the steel back, you could have some metallurgical problems within the welded areas or slightly beyond.
 
Agreed, there may be issues with the welding of the hood , and i will find out what kind of welds were done and deal with those problems later. Although if it were just welded and cooled then the steel is then in an annealed state and will be subject to premature wear. the danger of course if it were heated to correct temp and quenched to harden and not drawn back will likely cause fracture and breakage.
my concerns are with the upper lug fit with the slide. If i can slide a feeler through the first lug, what does that mean in terms of lockup at the moment of firing and when the slide moves back the short journey before the bullet leaves the barrel.. As the slide/ barrel move rearward , the lugs still contact the slide stop pin say at least .080 so that means the upper lugs are still in contact , further meaning that correct alignment is still established.... but where is the upper lockup then? it must be in the hood/breach contact that is holding the upper lock? right? nada? if not, how can i check to find out what lug surfaces are contacting ( i guess i can use layout dye ) but more important , just exactly what surfaces are supposed to contact and where.
i think we are getting close to problem
thanks for all patience
mike
 
Unlocked

Hey mike,

Let me throw a few numbers out and see what we can glean from that...
I think the answer is in the unlock/linkdown timing of your pistol.

When the pistol fires, slide movement begins as soon as the bullet moves,
though it's more sluggish due to the greater mass. The barrel and slide move together for a short distance, and unlocking begins. That distance varies
from gun to gun, but it occurs at roughly .090 to .110 inch of travel...and
the barrel STARTS to unlock. This is for ordnance-spec, or production guns.

To further enhance accuracy, when a smith sets up a match-type gun, he tries to keep the barrel locked to the slide for as long as possible...but there's a limit to how much it can be delayed...About .125 inch of slide movement,
but it can vary a little from gun to gun as well, depending on how everything stacked up when the pistol went together. Lower lug geometry and length of the link have the final say in exactly when the unlocking phase begins. Generally speaking, the longer the barrel remains locked into the slide, the better for accuracy. This will also serve to partly explain why we encounter
different accuracy levels in identical factory pistols...and varying points of impact too.

If your gun is starting to unlock early...at .080 inch of slide travel...that could be a big part of the reason for your accuracy issues. I've seen some factory pistols begin the unlocking phase so early that the shooter was
getting hot gasses blown into his face from the breech.

Unlocking begins, and the barrel starts to tilt. At about .250 inch of slide travel, the barrel is fully unlocked and down...or it should be...and there should be clearance between the top of the barrel hood and the underside of the slide's first lug...the one just under and forward of the bridge. Some
say that .005 inch is minimum, but I like to see .012-.015 inch or more. This clearance is necessary to keep the slide from knocking the top front corners of the locking lugs off.
 
mine starts to unlock at .080 and i thought it would be enough to keep it locked before the bullet left considering i use lead 200 grain bullet and i also use a full bomar rib making the slide/barrel rib heavier than normal which slows down the mass somewhat.... the slide is fit on the frame enough that the safety is just able to lock and then a little, the slide /frame fit is about flush but if i cut the lugs say just another .030 i would be in the .110 range (better i think) but what problems would i encounter if i did this?
thanks
mike
 
And to complicate matters even more …

When the barrel is designed and fitted to be cammed into its final position by the slide stop pin and lower lug pressure, the link has an oversized hole for the slide stop. Thereafter its only function is to pull the barrel downward to unlock it as the slide moves backwards. But depending on the size of the hole, and the distance between the holes in the link, the timing can be changed too.

Da’ Fuff will now suggest in his usual blunt and undiplomatic way, that if maximum bullseye match accuracy is what you want, you’re going in the wrong direction. Given what your present barrel has gone through I think it’s unlikely you will ultimately get the kind of performance you are looking for. If this pistol was an ordinary toy I’d say, “have at it,†but apparently this isn’t the case. Having been an active bullseye shooter at one time, and good enough at it to be a member of a State Team at Camp Perry for several years I know of what I speak. What you need to do is:

1. Dump the mis-named “gunsmith†that butchered and ruined your Bar-Sto barrel. :cuss:

2. Get a new barrel and have it installed by a real professional. Clark’s come to mind, and if I went to them I'd go by they're recommendation on what kind or brand of barrel to use. Or if you choose to use a Bar-Sto go to them. Most of the top 'smiths will return your pistol with a 50 yard/machine rest test target. Expensive? You bet! But do-it-yourself experimenting on match-grade barrels isn't exactly cheap. :scrutiny:

3. By all means, practice fitting a barrel (starting with the one you now have if you want) but go through the learning curve without starting on your best match pistol. Again, speaking from experience, you won’t likely get 2â€/50 yard groups on the first attempt no matter how you do it.
 
Refit

Hey Steve,

You might try cutting the lower lug a little farther back. I don't know if I'd take it as far as .110 inch though...I like to try to keep'em about .112-.115
but if your gun isn't heavily sprung, it may be okay. That would keep the barrel locked a bit longer. The amount of difference that it would make
depends a lot on how well everything else is fitted...and it would set the slide further forward on the frame quite a bit.

Fuff touched on another point that needs consideration. The link and the timing of the whole shebang. If the rear radius of the lug is cut farther back,
the link will pivot farther past dead vertical than it is now. If the link's position is now correctly about one-half degree past vertical....you may run into a little problem there if the clearance between the slidestop pin and the hole in the link isn't sufficient to prevent stretching the link. If the link gets stretched, it delays the linkdown timing of the barrel...and that could bring on problems with unlock and linkdown timing of the lug-bustin' kind.

Might be best to take Fuff's advice. Ditch the smith and find one who knows how to correctly fit the barrel for match guns. These things have to be in the right order. Sorta like an algebra problem. Once you go wrong, it's wrong from that point forward.

Luck!
 
practice fitting my own barrel (yes), go through the learning curve (yes) i only need one 45 ( wad gun ) there are hundreds of gunsmiths that can accurize a milspec gun to shoot 2 in., i just have to find out how and jump through the hoops, i don't mind.
I took it to another smith after the range yesterday and he checked centering of the barrel with brownells centering tool and could not fault the centering , he said the rear hood/breach fit was a kiss fit in length and decided that it was not excessively tite and the side clearances were not excessive considering the barrel is centered. He said the slide/frame fit was almost perfect , could not detect any vertical or horizontal movement ( showed me three STI pistols that all had a lot of felt movement ) the bushing has no movement in lockup. He did slide the slide back several times to feel when the lockdown started and wonder if he felt that is was marginal, but didn't say anything. the lower lug fit was sufficiently tite enough not to be an issue in his opinion. headspace is within spec. he checked the link and noted that it was likely a .288 link and felt that it was marginally tite when it gets to vertical during lockdown movement. He felt the pistol would be as good as he sends out his door
But, i think that .080 is not enough to keep in lockup , but hey, what do i know. So, you are starting to look elsewhere and my ammo is very carefully assembled with hard cast well filled out # 68 wadcutter 200 grain weighing 197 grain with lino added to the mix. tried 231 and bullseye with taper crimp to .468 and 4.1 bullseye giving the best group. Of course i have tried varied crimps powder amounts etc .
I'm kinda like a doggy with a bone here and i think that i'm almost there , seems that something simple is the culprit
thanks again for the courtesies
mike
 
I highly doubt that your ammunition is at fault, but just for grins you might try something else, and/or try the ammunition in someone else's pistol.

If you can, fire several bullets into a soft medium and then recover them. Use a good glass and look at the rifling marks to see if they are tapered and wider at the base. Forty-five pistol barrels have shallow rifling, and sometimes softer lead bullets will skid because of the torque. When this happened I could detect a difference in accuracy at 50 yards, but not at 25.

Bar-Sto barrels usually fit fine, and in my experience offer high accuracy. However, seeing what this particular one has gone through I wouldn't make any bets. It isn't the obvious things that are hard to correct, it's the others that require experience to detect.

Last but not least, test the pistol at 50 yards using a Ransom or similar machine rest. This is the only way to find out what the pistol & ammunition(and not the pistol/shooter combination) will truly do.
 
Actually, i had some metal that tested BH 23 and cast couple dozen bullets and carefully measured dia. and weights at 192 gr, picked ten best ( bullets were perfectly filled with with sharp bases, sized with allox/beeswax with the base rod center machined out to give a shoulder to seat on without interferance with the cutoff sprue, my seating die punch is also machine out so that the bullet is seated on the shoulder of the wadcutter for almost perfect alignment seating the bullet and l have seated bullet out enough about 1/30 in to give me a base/shoulder length about .906. These 10 rounds simply made a slightly smaller group. I was dissappointed with this result as i expected a huge improvement , but just wasn't there.
So , ok, guru's , dig deep, there is something in the gun that isn't kosher...
this gun, ammo combo should shoot one hole at 25 yds all day long
Tuner, you said that you don't know if you would go to .110, but you also stated that you like to keep it aroung .112 to .115, .... i dont get what you mean , so considering that i have only .080 , is that dicey? what would you take it to? give me a figure that you would do if it were yours and i'll try it and go from there, no obligation here, if it does't work i'll have it rewelded and do it over again
sidenote: i was machining a crankshaft for a 4 hp scratch build steam engine and i had 4 steps of different diameters for bearing surfaces and i made 9 shafts before i was happy,,,,,,,, so going to square one on this project is simple for me
later
mike
 
Last edited:
hmmm , no more answers , must be getting everyone down. OK, so i have done a test on the lockup. I put the pistol in my machinist vise without the spring or the link and fit a dial indicator on the slide and also another vertical indicator on the hood of the slide ( vert ind. reads tenths )
keeping thumb pressure on the exposed barrel while moving the slide back
.020 rear slide back ---.0015 barrel down
.045 ----------------.0005
.070 ----------------.001
.080 ---------------.0025
.085 ---------------.003
.090 ---------------.004
.095 ---------------.005
.100 ---------------.006
.110 ---------------.0085
.112 ---------------.0095
.115 ---------------.010
.130 ---------------.015


Looks like a slippery slope to me, if tuner likes his barrel to stay locked at zero drop with a slide movement of .112 to the rear, then mine drops almost ten thousandths ....... for every .001 error in 6 inches at the gun is 1/3 of an inch at 50 yards, so that would equate to over 3 inches at 50 yds and if the a fixed barrel will shoot good ammo at 2 inches then i would have an expected 5 inch group out of a machine rest !
so waddya think
i know ,,,,, either a new barrel or weld the lugs
so i guess the next question is what welding technique should i use , mig ok?
later
mike
.
 
Drop Test

Hey Mike,

Your barrel is droppin' pretty early in the cycle, but a lot of that may be due to the thumb pressure. Since the barrel would be held forward during live-fire, repeat the test by just letting it fall on its own, and use the link this time.

From the sounds of your first test, your lower lug seems to slope a little too sharply, since the barrel is falling at a pretty constant rate through the slide travel. You may be able to keep it locked a bit longer by making it a little
straighter without giving up a lot of vertical lock. It wouldn't take much
to keep the barrel locked to the slide to the .050 inch mark, which would just about cut your error in half. Might work...Might not...depending on how much vertical lock you lost when you flatten out the slope. It's worth a try, since you're either gonna weld the lug or rebarrel it.

Don't know a lot about welding stainless, I'm afraid. So many different grades of SS, and you'll just about have to know exactly what you've got
to make an accurate call on how...and what method to use. Maybe somebody that knows will chime in.

One little trick that has seemed to enhance accuracy while working on pistols
in which accuracy enhancement wasn't the object of the exercise...is the
fitting of a small-radius firing pin stop to the gun. It doesn't keep the barrel locked to the slide longer, but it does delay the slide for a split nanosecond...
which pretty much accomplishes the same thing. The results varied from gun
to gun...but most of the reports indicate that there was some difference.
That might also be an option, since accuracy comes from several little things working together toward one end.
 
OK I'll test again with the link installed.
looking at the first test, it pretty much stayed in lock until .070 which seems a little short , right ?and i was hoping you might say to cut the lug another .010 and try it , and maybe another .010 later until it corrects. I dont know the formula for calculating just how much rearward slide movement is critical, what seems to be the average ?
mike
 
Cutting more metal off of the lug will likely cause the unlocking to be sooner, not later. You need more metal where it isn't. :D

I know the firing pin stop trick can be useful with hardball, but I'm not sure how it would do with lighter mid-range target loads. In general, target 'smiths try to make unlocking easier with softball guns, especially those with Bomar ribs. Tuner ???
 
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