durbin6 wrote:
I had a similar problem with my XD .45 GAP. To test the mags I loaded my .40 S&W mags with .45 GAP rounds and the problem went away. I bought two new mags and havn't had any trouble since. I took my old mags to a friend of mine who works in a machine shop and had him compare them to the new ones and he said the lip spread was different. He adjusted them and now they work fine too.
I once had a 9mm that would occasionally have a failure to feed on certain magazines. A sharp tap on the rear of the slide would feed it into battery. Holding the slide, I very slowly (and carefully!) let the slide ride forward, and watched what happened. What I found was on the ‘bad’ magazine, the round would run into the feed ramp and stop! On the ‘good’ magazine, the nose of the round would start to rise up before it got to the feed ramp. The lips of the magazine weren’t letting the round come up soon enough. I spread front edge of the lips of the magazine slightly, to let the nose rise up earlier and haven’t had a problem since (several years, maybe 1000 rounds).
The shape, width etc. of the feed lips can be critical. As an example, I have a High Standard .22lr pistol. The breech face is almost completely flat. No feed ramp or other guide features. The round has to be guided into the chamber entirely by the shape of the magazine. I recently bought some magazines for it. Most of them work fine, but one keeps jamming. By running the rounds manually and slowly. I can see that the nose of the bullet is running into the top edge of the chamber. That tells me that the front lips need to be squeezed (to lower the nose) or the rear needs to be spread (raising the rear, lowering the nose).
I would suggest you do the same thing (maybe use snap-caps if you want) and see what is/isn’t happening between working/nonworking magazines. That should give you some clues. A little observation and common sense can take you a long way, and you often learn something in the process!
