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Discussion Starter · #1 ·
Does frame to slide fit really matter. It seems like the fit and consistency between the barrel and sights is what would matter. As long as the barrel is in the same place realtive to the sights it doesn't matter where the slide is relative to the frame.
I realize I may be missing something very important, if somebody could explain it I would be appreciative.
Thanks!
 

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Well, you're right. The alignment of the barrel to the sights is ultimately what affects your accuracy. So, how your barrel locks up is very important. Since your barrel locks to the slide, any play between the slide and frame translates into some play in where the barrel ends up. So yes, Slide to frame fit will affect accuracy.

If you read Kuhnhausen's book, it'll tell you that by far the most important factor in accuracy (mechanically) is the fit of the bottom barrel lugs to the slide stop pin.

Barrel fit, lugs to pin, hood to slide, barrel to bushing etc, accounted for something like 90% of mechanical accuracy. The other 10% was split up among some other factors, including slide to frame fit.

The way I understand it, you do a good job fitting the barrel and get a gun that shoots say 2" goups at 25yds. If you then make the slide and frame fit perfectly, you get up to 10% better, so now it shoots 1.8" groups. If my thinking is correct, it really tells you where to spend your time when putting things together.

Brian
 

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Discussion Starter · #3 ·
Great explanation! Thanks.
 

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PvtColt said:
Try building an accurate gun around a sloppy slide to frame fit and you'll find that it is important.
PvtColt, how about mentioning your experience in building/owning match-accurate 1911's and what results you've seen by tightening slide fit or not?

This is a topic of interest and jedibrain gave a good point of view with some thoughts on why he had the opinion that he did.

I'd like to read the details behind your assertion, please.

If a barrel is properly fit and the gun is shooting 2" at 25 yards, what improvement will I see if the slide/frame fit is tightened?

What methods do you use to tighten slide/frame fit on your guns? I find the subject interesting and you made a bold statement that indicates you have a lot of experience with this subject personally. Inquiring minds want to know.
 

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"As long as the barrel is in the same place realtive to the sights it doesn't matter where the slide is relative to the frame. "

A minor point: since the slide stop pin is anchored to the frame, and the lower barrel lugs rest on that pin (in a properly fitted 1911), slide frame fit does have a second order effect on accuracy since that error moves the location of the front end of the barrel relative to the slide a bit.

Like Jedi, I was told that barrel to slide fit (lugs, feet, bushing, etc) is about 90% of overall accuracy assuming the gun is eyeball sighted across iron sights. Bolt a red dot scope to the frame and then slide to frame fit becomes quite important since the sights are now referenced to the frame, not the slide.
 

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Assuming the sights are on the slide, the slide to barrel fit is most important. But as Bountyhunter says, the bottom barrel lugs rest on the slide stop pin, which is in the frame.

That engagement of the lugs and the slide stop pin is critical to accuracy and must be maintained until the bullet is out of the barrel. That happens just as the lug disengages from the slide stop pin. After that, nothing that happens to the pistol can possibly affect accuracy.

If the bottom lug-stop pin engagement is uneven or wobbly, or if the barrel is supported by the link, the gun will not be accurate. The link should be out of the picture and loose when the barrel is locked up, and is not, in fact, required at all for lockup. (The gun will lock up without the link; it just won't unlock.)

Let me make it clear that this is the ideal for accuracy. In the vast majority of pistols, the barrel will ride the link.

Once the bullet is out of the barrel, nothing the pistol does means anything in regard to where the bullet goes. But for that period in which the bullet about 4 inches, and the slide and barrel move around 1/8 inch, everything must be right, and be the same every shot.

Jim
 

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Jim Keenan said:
If the bottom lug-stop pin engagement is uneven or wobbly, or if the barrel is supported by the link, the gun will not be accurate. ....

Let me make it clear that this is the ideal for accuracy. In the vast majority of pistols, the barrel will ride the link.

Jim
You are correct. Mass produced 1911's "ride the link" because the parts are not hand fitted. Enough tolerance (read "slop") is designed in so they go together without much fitting. Not only do they ride the link, changing the link is often used to raise or lower POI because it's a lot easier to change that the sights.

As for accuracy: obviously, I'd rather have the lower barrel feet on the pin with the upper lugs just touching the slide.... but my Para barrel sets WAY up on the link.... and it keeps shooting like a tack driver anyway. I suspect the link is long enough that it "takes out" the slop of the link hole/pin and the barrel ends up pressed flush against the slide at the top. In lockup, the barrel is tight.
 

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Hello Gentlemen,

A looooong time ago I wrote a series of general random thoughts on the mechanical accuracy of a 1911 and accuracy in general. Forgive me, but the post is very long winded but some may learn something from it if they put up with my rambling. This post was preserved in the ‘how to’ section @ the link below.

http://www.1911forum.com/forums/showthread.php?s=&threadid=3856

Consider this: If we have a barrel tightly fitted in the slide and wedged tight on the slide stop pin, floating on top a loose ‘slide to frame’ fit.

After the trigger is pull, its quite possible the slide will move when the hammer hits, and the rotational torque of the bullet as it exits will also move the slide to an unknown location before the bullet exits the muzzle.

Hopefully, the slide will seek the same location for each shot. Wishful thinking???????? :rolleyes:
 

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Metal Smith said:
After the trigger is pull, its quite possible the slide will move when the hammer hits, and the rotational torque of the bullet as it exits will also move the slide to an unknown location before the bullet exits the muzzle.

Hopefully, the slide will seek the same location for each shot. Wishful thinking???????? :rolleyes:
I'd certainly believe the recoil would cause the muzzle end of the slide to rise as much as it's able in to it's "range of play" with respect to the frame. It would also rotate as you said because of the torque applied by the barrel twist. I believe the slide would do it the same every time.
 

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PvtColt said:
Try building an accurate gun around a sloppy slide to frame fit and you'll find that it is important.
You could turn that around and say try to build a reliable combat gun around a zero-play slide-to-frame fit and you'll find out how important some tolerance is when you're in a firefight...

I guess it depends on the ultimate use of the gun. For bullseye stuff that final 10% may be critical, but same for the "slop" in a purely defensive weapon...just some thoughts however simpletonian
 

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I think that after all is said and done on this topic it can be said that it really has alot to do with a guys overall knowledge of 1911's . I have been building them for years and I went from not worrying about slide to frame fit to tightening everything that left my shop Why? most people associate a loose fit with poor quality and or relevance to accuracy . I must say I love a nice fit of frame to slide but it has never proved neccesary unless the gun was in a Ransom rest . I learned this from the guys @ Novaks years ago but I still insisted on tight fit meant quality well I was wrong A good barrel fit was a must but a tight frame and slide has never been that beneficial . I must admit I have never had a complaint of my frame to slide fits compromising their reliability but I often wonder if my guns could run like JMB'S 10,000 round test without a glitch . Reasonble tight as Bill Wilson states makes alot sense but Les Baer tight as a standard is ass backwards and no I cant peen and squeeze no gun that tight ! . MikeO'Hara O'Hara Custom Guns
 

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I think where slide to frame accuracy myth came into pseudo real existence had to do with Ransom-rested guns. The Ransom rest holds the gun by the frame. The first shot is lined up and discharged. It is assumed some that the gun has remained in the same axis, save the change in trajectory as the gun pivots back during recoil. So the gun is simply pivoted back down for the next shot. This method works fine for a revolver or a gun where the slide to frame fit is tight. The trouble comes when the slide to frame fit is not tight and the slide is askew on subsequent shots compared to the original sighted first shot. The appearance is that the slide to frame fit affects accuracy. It does if you are using the frame as your fixed reference and not the sights, but shooters don't use the frame. They use the sights. As such, when firing multiple shots, a shooter resights each shot and a loose gun can be shoot accurately.
 

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Good discussion! Let's put forward some numbers:
So what are the tolerances (vertical and horizontal) for "sloppy" frame/slide fit?
how much for "normal"?
what is "good"?
and "excellent"?

I guess a target gun can get away with very tight tolerances, but combat guns not?

What about reliability under adverse conditions (mud, sand, water, grit, etc.), is tighter better, the opposite, or a happy medium? What about relief cuts into the slide for dirt to accumulate?

How long does a gun with large tolerances will shoot accurately, will accuracy degrade faster?
 

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I just made some numbers...

"If we have a barrel tightly fitted in the slide and wedged tight on the slide stop pin, floating on top a loose ‘slide to frame’ fit. After the trigger is pulled, its quite possible the slide will move when the hammer hits, and the rotational torque of the bullet as it exits will also move the slide to an unknown location before the bullet exits the muzzle."

Let's say a factory gun have about 0.010" side play (0.005" on each side). The slide run-out can be as much as 0.005" in the 3.5" long frame rails. This is a potential 2.57" error at 50 yds.
If the barrel is perfectly fitted over the slide stop pin, the slide stop pin is perfectly perpendicular and fits tightly on its frame hole, etc. then maybe we won't see all this misalignment, but the posibility is always there. And how many factory pistols have their bottom lugs perfectly fitted?
And there are still many factors left (barrel fit and quality, ammo, etc.) to further degrade accuracy.
I agree that many guns "center themselves" somewhat and group better than they should (most of the time), but you cannot build a super accurate gun with a loose gun.
 

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But, then, the sights live on top of the slide. If the slide's moving up, down, side to side with every shot, how much difference is there in where the sight is, relative to the eye, from shot to shot? I'm not a slide-rule cowboy, but I'd say that even a small fraction of a degree of difference at the slide would multiply into an appreciable difference at 50 feet. (Like TiroFijo said)

Pick up the phone. Call Les Baer, Ed Brown, Bill Wilson, Dane Burns, Chip McCormick. Ask them what's the first step that they take when they flop a slide and frame down on the bench to build a gun.
 

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A reasonable amount of movement is OK with me. I don't like slides that are real tight. I am not shooting bullseye and certainly not at 50 yds. But I put them in the -0 at 25 yds. Some need more accuracy than that. But you give up something for that accuracy.
 

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Reliability concerning a tight slide to frame fit:

I guess it depends on what you consider tight or how ‘tight’ and how the slide and frame been ‘tightened’.

I built a single stack Colt for a professional shooter that put 25,000 rounds of ball ammo through it without cleaning, just oiling it, without a malfunction. He returned it after the 25,000 for refinishing because the parkerizing was about 20 worn. The shock buff I put in was completely disintegrated into crumbs in the dust cover, so I know he never had the slide off the frame, and he told me he never cleaned it becase it was still working.

The slide to frame on the gun is not fit in the traditional crimp, squeeze and peen manner.

First, the slide rails are ‘blue printed’ ie, lightly machined true the entire length, all surfaces. Relief cuts are machined in the forward portion of the slide rails, so as soon as the slide starts rearward out of battery, it comes free with about .006 play, this is cut around the whole rail surface all the way around, which would be impossible to do with a file. Upon coming into battery it will snug-up the last 1/8” with no perceivable play.

Next the frame rails are welded and machined to match the slide rails. Relief cuts are milled through the center portion of the rails where they pass over the mag-chute, about .003, this prevents binding and gives a place for fouling to exhaust and oil to lay. Wear is reduced greatly because I’m running on a minimum amount of baring surface. I replaced the barrel after 50,000 rounds and the fit was still acceptable.

So far this gun is running fine in the east. Dunno how well it would hold up in the dust and sand, or in a swamp for a week. If ya'all remember Vickers posted results of a 'sand test', and he said the custom 1911 held-up very well.

Pete
 

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I don't really buy the "loose is more reliable" argument. I guess if the gun is extremely tight (to the point of binding) then maybe, but that's a mechanical problem.

Why is a loose gun supposed to be more reliable? Is it because dirt can get in it and it can still run? That's the only reason I can think of, but I think it's a fallacious argument. If you look at the slide and frame of a 1911, dirt can't really get in the grooves of a tight 1911. Like disc brakes (which are exposed and still work fine in the sand) there is no real way for much dirt to get in. Dirt could conceivably get in the slide grooves of a loose 1911 (although it would be improbable unless the gun was really loose), and I imagine it would stop it up if it did.

I have shot plenty of tight guns (quite a few were Baers) and plenty of loose guns. I have run them clean and I have run them filthy. I own both tight and loose guns. I have never seen any trouble that I could blame on a tight slide to frame fit. I don't drop them in the sand or mud, so I can't directly comment on that, but I think the tight ones would run fine if I did.
 
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