Help with a S&W MP40?

Question

I have had my MP40 for sometime and lately it is not feeding the last round of all 5 factory mags...
It locks open like last round has been fired..But still has one round in the mag.........

Answer 1

Do you keep your mags loaded up at al times?
Could be weak mag springs, but since you have 5 doing the same thing I would suspect the gun... but if the gun is locking open with one round still in the mag, you would think the follower isn't pushing up the slide release, but on 5 mags that is kinda hard to imagine, especially all at once.

Hmmmm

Answer 2

sounds like the catch on the slide release is bent down (or toward the rear) and is catching the follower to soon or the followers are defective and the round has somehow shifted and is sitting diagonally across the follower. if you look into the breach (slide locked open obviously) the catch arm should be on the right side next to the feed ramp, should be slightly higher than the bottom of the feed ramp.

regardless send it back to smith they are good about honoring their warranty, the customer service reps aren't very informative or helpful but the gunsmiths are good about fixing it and getting it back to you quickly, I got mine back in 2 weeks (who knew you could wear out a mag release spring in 2 months and 4000 rounds, guess I shouldn't expect a smith to hold up like a sig).

Answer 3

I had a problem with my S&W Sigma everythird round not feeding properly. Take a look at the extractor and ramp. I had a gunsmith file the extractor a little and re-polished the ramp.
It worked great for about two range sessions and then did the same thing. I made the change to Beretta. I will never get another S&W semi-auto. Good Luck.

Answer 4

Nikomat has the right idea send it back to Smith & Wesson. This seems to be a problem common to the S&W MP 40 I remember reading about a police departrment having a similar problem with their 40. cal MP pistols. Sig's work first time and every time I love mine.