Brownells 75th Anniversary - A Shooting Heritage

Building A 1911 - Part II

By Mike Watkins

The last article covered the items you would need to build your 1911-type pistol. If you want a refresher or didn’t get a chance to read the article simply go to Part I. This article will cover fitting the slide and frame of your 1911-type pistol.

If you have a slide or frame that is oversize on the rails, you will have to mill or file down the rails so the slide will go on the frame. If they will already go together, you may have purchased a pre-fit slide and frame assembly, so the fit is probably ok. If the components fit together and have a lot of play you may want to tighten the slide and rails on the frame. We will cover both procedures here.

The first step with an oversize slide and frame is to measure the width and height of the rails and grooves on the slide and frame. Write down your measurements, as you will need to refer to them as you proceed. It is easier if you will make a rough drawing of the rails from an end view of the frame and slide. This will allow you to reference the measurements you have made and visually see how they fit together and where material will have to be removed so the slide will go on the frame. Metal may have to be removed from all surfaces or only one.

Use a Slide/Frame Rail File. This file has safe edges and cutting edges on it so you can remove metal only from the surface that requires it. Proceed slowly and check your progress often. File evenly and square to the surface you are working on, you only want to remove enough metal to allow the slide to start on the frame, although it should be a little too tight.


Be sure you clean both frame and slide of all file chips and lube the rails with oil before installing the slide on the frame. This will help prevent galling and sticking the slide on the frame. Tapping the slide on and off with a soft faced hammer will help here. Don’t try to go too far or you will stick the slide to the frame and could damage them. This is not the time for a bigger hammer.

Once the slide will go on the frame, slowly continue filing and fitting until you can tap the slide to the rearmost of its travel on the frame. It should not go on hard or bind during its travel, but should be a little tight. This is strictly a hand feel or calibrated eyeball condition that you will have to determine.

Now that the slide will go the frame, lapping them to their final fit is next. I use Aluminum Oxide Lapping Compounds, that has 600 and 800 grit compounds in one kit. Start with 600 and finish with the 800 grit, of course. What you want to achieve here is the slide to move freely throughout its travel, smoothly and without any binding. Go slowly and check often, you can lap them so they are too loose. If that happens, you can follow the second part this article to tighten them back up! No play at all, but free travel is what you are looking for. You will have around a .001 of an inch clearance with careful work.

If you have a Milling machine, the procedure is the same, of course, just easier. It’s just a motorized file, maybe more accurate discounting human error. So that’s what it was when I misread the dial!

If you have started with a slide and frame that fits together but has a lot of play and is going to be a match pistol tightening them to remove excess play will be needed. Take your measurements as before.

On a carry pistol a little play is acceptable and perhaps preferable, your life or someone else’s may depend on it. We’re striving for 100% reliability in both!

The method I use is to peen or tap down the frame rails first. You will want to hold the frame in a sturdy bench vise with padded jaws and I use a magazine well filler to prevent crushing the frame. I have been using the Super-Hold Vise Jaw Pads for years and haven’t torn them up yet! I took a piece of Delrin and made a support to go thru the trigger guard to help hold the frame in place.

I then slowly tap them down with a 2oz hammer, with a mirror polished face. I like the 2 oz. Ballpeen Hammer, Model HP2 (56.7 grams). Don’t tap the rails down where the magazine opening is in the frame. The frame will collapse inward and the magazine won’t go in until you file it back open or the rails will crack. Peen the rails down from about 1 inch from the front of the front rails and about _ of an inch forward from the back on the rear part of the frame. As you peen down the rails a wire edge will form on the outside edge of the rails, this will have to be filed off as you proceed. Here again trial fit often and go slow.

Remember the measurements you took, there are hardened rail spacers you can use during the peen down procedure. You can get the Brownells 1911 Auto Slide Fitting Bar Set, or they are available separately, too. These are held into the groove on the frame as you peen them down and control how far to go. They correlate to those measurements you took. If you need a .115 inch frame groove to make the slide fit tight, just insert the correct spacer and tap away!

You can tighten the slide also; we have the Power Custom Slide Rail Tool.This is designed to allow you to SLOWLY tighten the slide by squeezing it so it will fit tighter on the frame rails. Here again do not try to squeeze the slide in the area of the ejection port. On the rear of the slide go slowly as the thumb safety notch is prone to cracking or breaking off. I prefer to peen down the frame only to tighten them up and leave the slide alone if I can. That’s probably because I have a Colt Gold Cup slide in my work bench drawer with a cracked left rear corner. But I have done a bunch of them.

You are working for just the opposite in the Peen down method versus the oversize component metal removal. But the end result will be the same. When the slide will just go on the frame a little too tight, and then follow the lapping procedure for that smooth travel of the slide without any binding.

Next month we’re on to step #3 – barrel and bushing fitting. There’s lots more to come and we’ll keep moving until we’ve got a complete pistol!


Building A 1911 - Part III