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9mm Feed Problem - Case Mouth Catching Chamber Face?


jlat32

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I finally got around to testing lighter recoil springs (8 lb only) vs the stock recoil spring in my 9mm Limited. Made the gun feel completely different, and I like it! Problem is that the 350 or so rounds I've tested with so far have resulted in three failures to feed. The first one happened in a match, so I slapped it back into battery and kept going. Didn't get a close look at it. The other two happened in practice, so I got a chance to take a closer look. It appears both times that the edge of the brass case mouth hit perfectly on the top of the chamber face and stopped the slide from going into battery. I haven't seen this malf with my stock recoil spring, so the only thing I can think of is that the 8 lb spring can't overcome the resistance of the case mouth hitting the top of the chamber face. To be clear, I'm not talking about the malf where the cartridge is pinned completely against the feed ramp and the nose of the bullet is hitting the chamber face or stove-piping.

I have run a mix of 147 and 124 handloads, as well as 124 and 115 gr factory loads. The two failures I observed closely were with a 147 handload and a Fiocchi 115 gr factory load. I haven't had any magazine-related malfunctions (that I can recall) with the stock recoil spring, but I decided to check the feed lip spacing. My "well used" mags were about 0.360" at the front and 0.355" at the rear. My newer, less used (less than 10 times) were pretty consistently parallel at 0.355". One malf happened with a "well used" mag, the other happened with a newer mag.

Total round count on the gun is around 4500 +/- rounds.

Anyone ever experience this? Any recommendations? I was considering polishing the feed ramp and inside edges of the chamber face, but wanted to make sure this was the direction I should go or if I have a completely different problem all-together.

Thanks.

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I was going to suggest that it could possibly be too little "crimping", but you had the

same problem with a factory load.

Suggest you try a 9 lb spring??

Frustrating, isn't it? So many possible causes ... Just have to check them out

one by one. :cheers:

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A more heavily sprung gun will be more forgiving of rought spots in the action; if you want your gun to run with light springs you need to smooth it out wherever you can.

It's amazing how different a really smooth action feels when shooting.

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I had the same problem with an Elite. Check the round below the round that is jammed. There may be a gouge in the case where the bottom of the slide has had a chance to dig in due to the slower slide speed. I slightly rounded and polished this edge and no more jams. When the gun is jammed drop the mag and if the round chambers this could be the problem.

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  • 2 weeks later...

Update: I detail stripped and cleaned the whole gun as it was long overdue. Then I slightly rounded the edges of the chamber mouth and kept the 8# recoil spring in. During a practice session where I fired about 200 rounds, I had two hangups where the bullet nose was stuck on the feed ramp. I had recently tightened up the feed lips on my mags a bit, so I could have shallowed out the "approach angle" of the bullet being stripped out of the mag, causing it to wedge against the feed ramp and the 8# spring couldn't push it through.

I ordered some 9, 10, and 11 lb recoil springs to play with, but for the mean time I went back to my factory recoil spring until I get some free time to check the feed angles of my mags again and test other springs. I shoot it a lot better with the lighter spring, but I'll take reliability over marginal performance improvements at my level. Over running shooting positions or not being up and ready entering a position cost me more time than the tenths I'll gain with a perfectly sprung gun. At least that's what I'm telling myself...

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This sounds like a reloading issue. What die are you using to resize? If you have some Glock bulged brass, this can happen. The 8# recoil spring is the correct one for what you are doing. In EVERY case I've seen where there are loading failures, its the ammo. Rounds loaded way too long, not enough crimp on the mouth, and sizing die not going down far enough on the case are some of the reason why an 8# won't work, so check those.

Putting a heavier spring in just makes the gun run like crap.

Edited by Nealio
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Nealio,

I haven't had the "catching the chamber mouth issue" since I rounded and polished the perimeter of it. With that malf I would agree that it might have been ammo, then I had it happen on a factory load too. At any rate, smoothed the chamber mouth and haven't had a rim catch...yet. The recent malfs with 8# spring were similar to nose dives, so I was going to check feed lips again and polish the feed ramp, which I haven't done. If you think I should look elsewhere, please advise.

I reload with a Dillon SDB, so they are the SDB proprietary dies, I guess. The recent batch of 124 and 147 loads using Xtreme bullets round nose were OAL 1.168" and crimped at 0.377". I've had one fail to go into battery as a result of bulged case bottom over about 3k rounds, and that was with the stock recoil spring.

Putting a heavier spring in just makes the gun run like crap.

No doubt there! Love this gun even more with the light spring! Just being conservative as next week I have my last big match for the year. After that I'll tinker all day. Still going to check my mags again though. Edited by jlat32
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too long for me too.

Yeah seriously I' have a newer stock II, It will not chamber my 135's if I load them much longer than 1.100. I understand that the older stock II's have a more forgiving chamber.

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  • 2 months later...

Update:

Over the past couple months I shot somewhere between 750-1000 rounds of the "long handloads" mentioned earlier, as well as factory ammo. Probably around 70/30 in favor of the handloads. I had polished the feed ramp and changed out to a 9-lb spring and have had zero feed malfunctions during this time. Have not tried any lighter springs as it seemed reliable for how little I shot it, and felt pretty good with the 9-lb spring.

I am planning to shorten up my reloads in the future, but haven't loaded much in the last couple months.

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