Point your 1911 toward the fellow on your left (just kidding). Seriously, point the muzzle left.
Let's call the muzzle the front, and the other end the rear.
As you look at the slide stop cut on the side of the slide, you will notice that the front is rounded and the back is straight, with a sharp corner of around 90 degrees at the bottom of the slide where it meets the frame. Lock the slide back and observe how the surfaces of the slide stop and slide stop cut "mate" with one another. (No giggling in the back.)
Write this down: The back of the slide stop cut must be close enough to the back of the pistol to allow the slide stop to rise easily into the cut when the mag is empty. If the cut is too small or too far toward the front of the slide, or if the slide stop is oversize, this will not be the case.
The appropriate remedy depends on the fit of the parts and whether any significant damage has been done to the (about) 90 degree corner on the back of the slide stop cut. If this corner has three sides instead of two, the slide stop is increasingly less likely to lock into the cut and lock the slide back, especially if the fit issue is not addressed. It is likely to continue to hit low on the cut, wearing away more metal on the rear of the slide cut, turning the (about) 90 degree angle into a (about) 45 degree angle.
It is preferable, if there is no damage to the slide cut, to work only on the cheaper slide stop. If you must restore the slide cut to a 90 (about) degree corner, you will need a very small square or triangular file. Metal should be taken off the rear of the cut by drawing the file down at an angle corresponding to the proper angle of the rear of the slide stop cut (about 90 degrees). This will take patience, very slow removal of material, attention to filing at the proper angle and depth of cut (don't cut into the "flat" of the cut, or add any new angles or file marks to the slide).
If you are lucky, all you need to do is to fit your slide stop. You can do this by removing enough metal at the rear of the stop, preserving the 90 degree angle there, to allow the stop to rise freely into the cut. You can also enlarge the slot in the top of the slide stop if necessary.
Removal of too much metal will result in a sloppy fit, rattling, and the slide stop falling out on its own.
It is essential that you
1. be patient,
2. remove only a small amount of metal at a time
3. reassemble the frame (with mag inserted), slide and stop frequently to check whether you are finished.
4. stop removing metal as soon as the slide stop starts functioning properly.
5. concentrateand have good light.
You will have to do this when the wife and kids are out of the house and the dog has been fed. You will need between half an hour and two hours.
I have done this twice, once on the slide cut and stop and once just on the slide stop.
Do not work on the slide unless you have to.
Regards.
[This message has been edited by Ledbetter (edited 06-09-2001).]