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Discussion Starter · #1 ·
Can someone explain to me when they say that they had the slide fitted to the frame what that means.

I know that the slide does not have the play in it but how and what do they do?

Also, how does a barrel bushing make that much difference in the guns performance. It would seam to me that the bushing and barrel would have to be machined together to get the performance you might want.
 

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Can someone explain to me when they say that they had the slide fitted to the frame what that means.

I know that the slide does not have the play in it but how and what do they do?

Also, how does a barrel bushing make that much difference in the guns performance. It would seam to me that the bushing and barrel would have to be machined together to get the performance you might want.
I am certainly no smith...or jones but how do you know the slide has no play in it?

As far as what 'they' do....I believe it involves some skilled welding.

The barrel/bushing question I will defer to one of the real smiths here but would assume the bushing would be machined to some tight clearances with the muzzle.

Now can I interest you in a slightly used bridge?;)
 

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You begin with a slide and frame with slightly oversized rail dimensions, such that they will not initially fit together. Through careful measurement and removal of metal in identified regions one can get the slide to begin to fit on the frame. Once you have a partial fit one can use lapping methods to remove high spots so that the slide will fit and glide smoothly on the frame's rails. Careful fitting can produce a slide to frame fit that has no horizontal or vertical slop, and move as smooth as glass.

A properly fit barrel bushing allows a tight fit between the bushing and the slide, and the bushing and the barrel, such that there is no movement of the front of the barrel when the slide is in fully battery. It's the slop, or free movement of the barrel either at the front or the rear that degrades accuracy, i.e. the barrel does not point to the same place for every shot. The point is to have the barrel in the exact same position every time for every shot so that it points to exactly the same place.

All of these procedures are required to maximize the mechanical accuracy of the gun. The accuracy of the ammo or the shooter are two completely different issues that are addressed separately.

Edit: You can also start with a gun with sloppy slide/frame fit and bend and hammer the rails until they fit tight together, or fit them via accu-rails. The end result is the same.
 

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A "loose" slide certainly does have play in it. That is where the "fitting" comes in. Closer tolerances on the frame rails allow it to ride as close as possible to the slide.

Barrels also need to be fit properly, as does the barrel bushing to the frame, and more importantly - the barrel. The barrel and bushing don't have to be machined together, but they do have to have specific tolerances for optimum performance and accuracy. The bushing needs to fit the frame snuggly. It also needs to be fit to the barrel fairly snug, but not so tight as to allow the barrel to be bound-up and be "sprung" by the bushing when the barrel unlocks during cycling. If you know how to fit a bushing to a barrel (and slide), the two parts do not have to be machined together. You can file and stone the bushing to get the exact fit you need for any given barrel and slide.

That's what you are getting when you buy a custom gun - a superior level of parts fitting. And you get better accuracy as a result. Typical out of the box guns are not fit as precisely for the most part, and may not be as accurate.
 

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There are two or three ways to fit frame and slide. In the old days, the slide was squeezed in a vise to remove lateral clearances. The rails of the frame were peened down with a hammer to remove vertical clearances. This is more of an art for a blacksmith than a gunsmith. Slides could be cracked or collapsed using this process.
You can buy "oversize" frame and slide and remove metal until the slide and frame fit with nearly zero clearance.
You can weld up slide and frame and remachine for zero clearance.
You can mill the frame and install a set of rails.
The accuracy of a pistol is determined by the barrel being in the same place and pointed at the same POI each time the pistol is fired. With tolerances in the slide /frame reduced the repeatably of the barrel position is held consistent.
You are correct in your thinking that ID of the barrel bushing needs to be the same as the OD of the barrel with minimal clearance.
A rule of thumb is that .004" of clearance within the pistol equals 2 1/2" at fifty yards.
 

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Slide rail channels can be 'hammered' down to fit the frame tightly - Brownells sells a set of bars for this purpose - they hold the shape of the rail while peening so it doesn't collapse and is the same dimension along the length of the slide:

http://www.brownells.com/gunsmith-t...ols/1911-auto-slide-fitting-bars-prod842.aspx

I don't know how well they work, but they do have both a PDF of instructions and a short video showing how to use them.


dakotaTex
 

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Discussion Starter · #7 ·
DakotaTex, that was interesting video.

Was wondering if the frame rails are too tight, how do you open them up? Or do you work on the slide instead?

The mic. that he used to measure the rails, any idea on what it is called. I can not imagining buying one because my guess they would be very expensive. Also looking for the material/device that he used in his vise.

Thanks,
 

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First let me admit that I'm no gunsmith. I'm just a fascinated spectator in their thrall. I've never done the first thing on building a gun (although I have it on good authority that Santa is bringing me a low end RIA to learn on). I would like to hear what the real gunsmiths on this forum say about my comments below.

Here's a video of a guy who used the lapping technique to get the slide to fit the frame (http://www.youtube.com/watch?v=mpuHVpbIwmA). The result was a sloppy fit. I believe the reason is because this method is inherently unbalanced. A lot more lapping occurs at the end you're beginning at than it does in the middle of the slide or at the other end. Instead of an even amount of lapping occurring the full length of the rail you end up with too much at one end.

Seems to me he could have minimized this error by doing an equal amount of lapping from each end, but even then, the amount of lapping at the ends would exceed the amount in the middle of the slide.

I suspect the proper use for the lapping technique is to first use files to remove the bulk of excess material, and to only then do the final fitting of the slide and rail by lapping.
 
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