.22LR Ammo bulging


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fireman5069
September 13, 2010, 09:14 PM
I shot a brand new Phoenix Arms HP22A today( yeah, I know). Noticed the bottoms of the rims opposite the firing pin strike were bulged. Anyone know what causes this? Ammo was CCI Minimag 1280 fps and they worked fine in my other ones with no bulging. See attached photos if they will load.

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dawico
September 13, 2010, 09:21 PM
It appears to be a chamber issue. Does that bulge line up with the feed ramp? It looks like the case isn't supported right there.

fireman5069
September 13, 2010, 09:32 PM
I'll have to check that. I've heard that I should be using standard velocity rounds in it but others are using the same as me with no problems. I have other .22's so it's not a major setback.

GLOOB
September 13, 2010, 10:00 PM
I had the exact same thing happen with my HP22A when new, using Federal Auto Match. So I know that if you turn the brass over, you'll find the FP dot on the opposite side of the rim from the bulge. I did some tweaks to my gun, and this went away. I'm not 100% sure about how or why, but I have a pretty solid theory.

Check the notch that is cut out of the breech where the extractor fits. It's a tight fit. On mine, you could see where the extractor actually got pushed out a little by this notch when the slide was returned to full battery. But if the slide was slowed by the chambering of a round, it is conceivable that instead of the extractor getting pushed out, the slide might get hung up just a tiny hair out of battery, instead. I took a file and deepened this notch just a tad so that it wouldn't contact the extractor. Actually, if memory serves, I didn't have a file thin enough to fit, so I ended up using a Dremel, a cutting disk, and a really light touch.

Yes, it seems ironic. To stop the brass from bulging you have to remove a little bit of the chamber support. :) But I am pretty sure that was the cause in mine.

Check the jimenez arms forums for more info on tuning up this pistol.

fireman5069
September 15, 2010, 04:10 PM
Shot again today with Remington standard vel. rounds and did not have the problem. Think I will keep it for a while and see how it does with other standard rounds.

writerinmo
September 15, 2010, 05:20 PM
Never had this problem with mine, but never shot the hot stuff.

rcmodel
September 15, 2010, 05:33 PM
Looks for sure like an unsupported chamber due to the feed ramp cutting into it.

Don't shoot any more of that ammo in it for sure.

rc

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