1911 Slide To Frame Fit

S

Secretariat

New member
Forgive the ignorance as I am still new with 1911 pistols. Anyway, what let's say if after so many thousands of rounds, the slide to frame fit of your 1911 pistol become loose, is there a way to have them tight again? If yes, what procedures are done? Also, assuming that the slide and frame of your 1911 are tight again, how long or how many rounds shall it take for them to become loose again?
Thanks in advance.
 
A gunsmith can adjust the slide (squeezing it) or add something to the frame to keep the fit tight.

If you've noticed a change in accuracy or precision, you shouldn't automatically assume that it is due to change in the gun's slide/frame fit, even though it seems to be more loose. (Some guns with very loosely-fit frames can be tack drivers.)

While it wasn't the case 10-15 years ago, many 1911 owners and gunsmith, nowadays, argue that slide/frame fit accounts for a very small part of a gun's total accuracy/precision. If you use the sights on the slide, the key is consistent barrel and slide lock up. If you are using optics attached to the frame, then slide/frame fit is a good bit more important.
 
The traditional way of tightening the fit was to hammer on the frame and squeeze the slide in a vise, and that is still done, but if I were going to (again) spend money on refitting a slide and frame, I'd go with precision welding and remachining.
The peen/squeeze method usually results in tightness that quickly wears again due to small areas of contact; edges running on edges.
My peen/squeeze fit was tight for only a few thousand rounds, and I don't think it's as tight as the original, factory fit after 20k rounds.
The weld and remachine should result in bearing surfaces that are not only long, but with much larger areas of contact that will last longer.
 
Secretariat said:
Forgive the ignorance as I am still new with 1911 pistols. Anyway, what let's say if after so many thousands of rounds, the slide to frame fit of your 1911 pistol become loose, is there a way to have them tight again? If yes, what procedures are done? Also, assuming that the slide and frame of your 1911 are tight again, how long or how many rounds shall it take for them to become loose again?
Click to expand...
Are you asking because you think you have a 1911 that has become excessively loose, or are you asking what to do **IF** your 1911 eventually becomes loose? How do you use your 1911? IMHO, if you aren't a bullseye shooter who is seeing degraded accuracy that's absolutely due to slide/frame wear, I wouldn't mess with it. Frame rail peening and slide squeezing are not tasks to be undertaken by novices, and not many gunsmiths today are qualified to perform them. The result could be a lot worse than where you started.
 
If your slide becomes 'loose' after many thousands of rounds, you'll very likely be in need of more than just squishing the slide. Most likely be a complete rebuild. Comes down to diminishing returns.
"...Frame rail peening and slide squeezing are not tasks to be undertaken by novices, and not many gunsmiths today are qualified to perform them..." Absolutely. I've seen slides squeezed in vices so much the thing wouldn't move. Ain't no fixing that either.
 
Without knowing how much horse sense you have about shooting, loss of accuracy generally isn't due to frame to slide tolerance.
If it were, polymer framed striker fired pistols would be shooting around corners.
Shake them and they rattle, but they can still shoot really good.
 
Slide to frame fit has little to do with accuracy with a 1911. The sights are attached to the slide, so slide to bushing and bushing to barrel fit are far more important for determining accuracy.

Jim
 
Looseness is related to bearing surface. Basically if you cut a square to slide inside a c channel, it will wear until a balance is achieved. That balance is the gun self fitting the slide to frame until wear mostly stops. Otherwise known as break in.

Original guns were cut looser and the cuts were less accurate. So, guns would break in until the actual bearing surface supported the sliding wear forces. This resulted in a loose gun.

Modern low to mid priced guns are cut much more accurately. This means minimal break in and therefore tighter guns overall. You will most likely NEVER shoot a modern gun loose.

Above the $1000 mark, there is some fitting which minimizes break in and wear even more.

Also, somebody should have mentioned accu-rails. As they are another way to get this precise fit.
 
Jim Layton is correct in that slide to barrel fit is more important that slide to frame fit, but the fit of the barrel to the slide is not important just at the bushing. Also very important is fit of the barrel to the slide at the rear, where the barrel hood interfaces with the slide and the barrel locking lugs interface with the slide lugs. Fit of the barrel foot cam and the link with the slide stop is also important. The name of the game for accuracy is consistency. As an old gunsmith once told me, "It doesn't matter if, when the gun is fired, it jumps up in the air, turns over three times and comes back to your hand, IF IT DOES THE SAME THING EVERY TIME!"

Jim
 
Accuracy in a 1911 comes from the following according to Jerry Kuhnhausen, in his 1911 Shop Manual:

Mechanical Accuracy Features: (repeatable lock-up):
20% eliminate rear barrel play.
20% consistent vertical lug lock-up.
20% barrel / slide bushing fit.
15% frame / slide play.
10% match grade barrel.
10% headspace.
5% unreachable.

Shooter Assisting Features:
50% good trigger.
25% good sights.
25% Misc., like good ammo, grips, etc.

So 15% comes from the slide to frame fit.
 
Yep, and 70% comes from barrel to slide fit (20% rear barrel, 20% lug lockup, 20% barrel-bushing; and 10% headspace).

Jim
 
. Anyway, what let's say if after so many thousands of rounds, the slide to frame fit of your 1911 pistol become loose,
Click to expand...
Then you might as well reckon that you've worn out your pistol and it's time to
replace it with a new one.
 
20% eliminate rear barrel play.
20% consistent vertical lug lock-up.
20% barrel / slide bushing fit.
15% frame / slide play.
10% match grade barrel.
10% headspace.
5% unreachable.
Click to expand...
These are very quotable figures indeed,Kuhnhausen does not explain how he
calculated them and then there is the 5% unreachable factor.Some good material in those manuals but there are some ringers too.
 
I doubt those figures can be totally supported; at best they are educated guesses. Still, they seem to confirm what many of us have seen over the years, but never tried to quantify.

Jim
 
More recently, I've heard other figures cited for the role of slide/frame fit in precision -- and 8%-10% seems common.

But isn't this really talking about Ransom Rest results, and not aimed fire? There may be something else at play here, and I'm exposing my ignorance -- certainly not the first time -- but I simply don't understand.

Back to the earlier point -- if you're using the sights on the slide, and the slide/frame (and sights) align consistently when the gun is cycled, why would slide-to-frame fit play even that big a role?

There are guns that have loose slide/frame fits but shoot very accurately. Most of the polymer-framed guns have reasonable slide/frame fit, but don't always come back to the exact same slide/frame locations, thanks to the give in the polymer. But some of them are very accurate.

That's why Ransom Rest tests are not used as much with polymer-framed guns as with metal-framed guns. Polymer frames affect the gun's precision -- its ability to return the entire assembly to the exact same place with each shot. A RR test measures a gun's precision, which is its ability to return it's part to the same place with each shot. The sights aren't used.

If you take one of the best 1911s, and put that top-end slide assembly on a frame that is more loose, I would expect sighted fire would be about the same for either frame, but would expect the Ransom Rest results to be much better for the slide and frame that were a matched pair.

It's only when you put the gun being evaluated in a Ransom Rest, it seems to me, that slide/frame fit becomes critical. Or, when the sighting system used is mounted on the frame. Then it could make a difference.
 
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I've read that one old-time pistolsmith - I want to say it was Austin Behlert - made a scope mount that conformed to the top of the slide.
The gun would be placed in the machine rest, then the scope/mount would be rested on the slide and the rest adjusted, if necessary, so the scope was on target. The scope would be removed, a shot fired, repeat.
Using a scope mounted to the slide helped ensure that it was the barrel/slide alignment that was being measured, reducing the influence of shot-to-shot variations in the relationship of the frame to the barrel/slide/sight fit and alignment.
I've also heard that some people can "outshoot a machine rest", which reinforces the idea that locking the frame into the rest isn't necessarily going to result in the best accuracy.
 
In all practicality unless you have an odd / poorly built 1911 by the time this happens to a personally owned 1911 one of conditions will be met:

A. You will have 5 others and retire your old friend to a place of honor

B. You will have a spot in line with a top smith who will weld / re-machine your old friend to as good or better than new.


All joking aside it takes serious effort to wear a 1911 out and any number of other items on the gun will need attention as well.

I agree 100% that welding and reprofile of the surfaces is the only long term solution to tightening fit however I have looked at a number of the old squeeze and swage guns and they can be very respectable esp. If one is judging relative to other guns of the era.
 
I believe it was Ed Brown that did the math in an article about mechanical accuracy in a 1911 and showed where the slide to frame fit contributes very little.

I was taught about 5% at most and I believe that's what Ed came up with also.

There's two good ways to tighten slide to frame fit, Accu-rails or weld and machine the rails to tighter tolerances, the other methods do not last long and are a waste of time.

A good barrel and barrel fit is the most important thing to the mechanical accuracy of a 1911, to quote my Mentor when we were discussing mechanical accuracy "the barrel has to be hard fit, as tight as a bank vault at both ends", that was his thoughts and they are true if you want to cut X's.
 
One usually overlooked factor in slide to frame fit is the affect on the barrel lockup (locking cam fit). The barrel is in the slide, but the slide stop/cam is in the frame. If the slide to frame fit is such that the action of camming the barrel into lockup can actually move the slide upward, or pulling the trigger can move the slide upward (as in the BHP), accuracy will suffer. In the 1911, the link fit is another complicating factor and the lockup can be affected if the link forces the slide upward relative to the frame when the barrel locks up.

Jim
 
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