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MP40 Ammo Selection

fishermankw

fishermankw

Senior Member
Was running a C&R MP40 and had a couple smoke stacks when firing. Was shooting brass cased, FMJ mag tech. Was told a “hotter” ammo might help prevent this. Does anyone have any suggestions. Was looking at Winchester 9MM NATO which is a little hotter, but also don’t want to wear anything out. TIA!
 
Was this while you were using your original bolt? Or the replacement you had talked about installing?
I’ve never had a stoppage with mine even running Wolf junk through it. They are not easy to break. I’ve had it so filthy that I needed a gallon pale of mineral spirits to get all the lacquer scrapings out of it.
 
biggymu said:
Was this while you were using your original bolt? Or the replacement you had talked about installing?
I’ve never had a stoppage with mine even running Wolf junk through it. They are not easy to break. I’ve had it so filthy that I needed a gallon pale of mineral spirits to get all the lacquer scrapings out of it.
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Swapped out the original bolt and original firing pin assembly. Got a couple that worked well together and functioned fine outside of the gun. Plenty of clearance in the tube and within the bolt. When I take it out again could try another bolt and see if that makes a difference.
 
I’ve ran various kinds of 115 and 124 gr from various manufactures, steel and brass cased, never had any issues, it ate everything. If I remember correctly though the 124 gr is close to the German spec.
 
If it is feeding properly, stovepiping sounds like maybe low powered ammunition. Wolf and the like are under loaded and the MP40 likes it hot. The face / angle of your ejector is important as is the grip of the extractor. You aren’t going to wear out anything on it but the recoil spring, ejector, and extractor.
 
Hambone said:
If it is feeding properly, stovepiping sounds like maybe low powered ammunition. Wolf and the like are under loaded and the MP40 likes it hot. The face / angle of your ejector is important as is the grip of the extractor. You aren’t going to wear out anything on it but the recoil spring, ejector, and extractor.
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It was a couple boxes of lower mag tech brass case. I’ve heard it likes the hotter rounds, picked up 100 round box of Winchester NATO going to give that a try and see if the problem goes away.
 
I’ve had good luck running everything but Wolf 115 FMJ because it’s light light loaded. May even be almost subsonic. You should be able to reliably run everything but very light loads or short bullets. Win. Q4318 124 NATO should be almost a standard, that is, if your MP.40 won’t run that reliably then you’ve likely got: 1) bad / worn recoil spring; 2) bad recoil tube geometry; 3) bad ejector; 4) bad extractor.

The recoil spring is important. Too light and it may allow light loads to run without running away, but it won’t feed forcibly enough (it’s an open bolt weapon). Too stiff of a spring and it won’t run anything but +P and +P+. The mag springs are very important and the feed lips too. The mag (double stack, single feed) is the weakest part of the design. We and the Brits copied it (!) The trick is having good strong mag springs and making sure the feed lips allow the top cartridge to have a slightly nose up bullet orientation so that it leaves the magazine slightly upward into the chamber.
 
heavy_mech said:
Highly recommend. NATO headstamped and fairly hot. Just ran a few hundred rounds this Saturday.
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Everything today (except military/police not sold to the public) +P+ is loaded light. I have a stash of Federal 9mm BPLE +P+ 115 jhp and it's awesome, super accurate, super hot, but also a really nice recoil impulse. Way back in the day, like 15 years ago, I bought a bunch, like 10000 rds., of Israeli surplus 9mm they used in their Uzis, +P+ super hot. It's mixed lot, was tumbled, has some Arabic 9mm in there, for $69/1000. I'm running up on the last couple thousand rounds. It's impressive out of an SMG. MP.40 loves it. I shoot it with all my shooter parts. It would likely peel the hood off a Glock. I would never, never, never shoot tumbled rifle ammunition of any flavor like this, nor would I run this in any pistol. Maybe a Cz.75. You can definitely tell a difference shooting snappy +P and +P+ in a MP.40 over regular stuff, such was Winchester white box and regular commercial loadings which putt putt putt. Wolf 9mm 115 will make a regular MP.40 run away. That is, the recoil will drive the bolt back far enough to eject, but not far enough back to trip the sear. Thus you get a putt putt like 30 times with one pull of the trigger. That stuff sucks, but I bet on a chrono it's subsonic out of a pistol.
 
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