The question of why magazine catches don't function smoothly and easily are not uncommon. So, I thought I'd put together a simple pictorial guide to help folks out. It's the little things that make a difference and elevate your pistol above the ordinary.
The magazine catch consists of three parts: the catch, the lock, and the spring. Each of them interact with the other two parts as the magazine catch is pushed in by the thumb or magazine and then returned to its starting position by the spring.
The key to smooth operation is careful filing and sanding of the sharp edges of the contact surfaces.
The Magazine Catch
In my experience it's rare that a magazine catch will not fit into the frame. To test this remove the lock and spring then insert the catch into the frame. If it will not drop in and drop out of its own accord, you will need to determine where the contact is happening and eliminate that contact using a dowel or punch wrapped with a piece of 320 grit or finer sandpaper if you're working inside the frame or a flat file wrapped with sandpaper if you're working on the magazine catch.
That was the easy part.
Now we shift our attention to the inside of the magazine catch.
In the image below we're looking into the machined hole into which the spring and lock fit. That interior surface should not have any edges that can cause roughness as the lock and spring move across them. A dowel or punch wrapped with sandpaper will take care of any roughness in the hole. Progressing from 320 grit up to 2000 grit sandpaper will result in a very smooth surface although going beyond 800 grit may not be necessary.
The next surfaces to address are the sides of the slot that run from the opening of the hole into the magazine catch. These surfaces are in constant contact with the lock tab as the catch moves in and out. Once again, we want to eliminate any roughness. A flat piece of steel such as a feeler gauge can be wrapped with sandpaper to take care of these surfaces.
One note. The six sharp corners where the slot meets the rounded portion of the catch should be lightly rounded just enough to break the edges. I've found Grobet 6'' Die Sinker Riffler files to be very handy when working inside confined spaces. Here are links to some of the files I use:
31.845 - Cut 6
31.8646 - Cut 6
31.875 - Cut 6
Below is close up from a different angle of the two slots into which the lock tab fits and travels. The orange lines highlight the 90° edges that should be slightly rounded and smoothed to prevent the edges of the lock tab from hanging up as the catch moves left and right in the frame.
The Lock
Next is the lock. This is the most difficult part to address because of its size. The yellow shaded areas all need to be smoothed since they all make contact with either the catch or the spring. Once again gently rounding the sharp edge where the area meets the next feature will pay dividends. In this case the sharp edge is where the wide part of the lock meets the spring shaft.
Often the very end of the lock that is inserted into the spring will not be adequately round to avoid the edge from snagging on the spring coils. Here the end has simply been beveled. I always round the end into a dome shape with a smooth transition between the dome and the shaft. No sharp corners anywhere.
The tab that bears against the slot in the catch also needs to be flat and smooth with no sharp corners.
Magazine Catch Interaction with the Magazine
Sometimes seating a magazine in the pistol will require more effort than should be necessary because of the geometry of the catch at the yellow area seen below. That are can be a simple bevel as shown below or it can be more complicated by rounding, smoothing, and polishing the area. Examples can be seen here:
https://forum.m1911.org/showthread.p...agazine-Catch) ,
https://www.1911forum.com/threads/an...#post-13771171
When modifying the catch care must be taken to insure that magazine support is not compromised by removing too much of the catch shelf. You can check the amount of catch engagement with the magazine slot by removing the slide, removing all the magazine guts, seating the magazine in the frame, then looking down into the magazine tube and observing the catch shelf.
Sometimes the magazine catch will prevent the magazine from dropping free when it is pushed fully inward. Instead it will make contact with the magazine and pin it against right side of the frame. The fix is straightforward. Relieve the yellow area seen below. As with all other fitting operations it is best to proceed slowly with frequent test fitting.
The Spring
Last up is the spring. The end coils often have sharp edges. These can be removed. Some folks will actually run cylindrical felt bobs covered with polishing compound through the length of the spring. I've never tried it so can't comment on its effectiveness.
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