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Discussion Starter #1
So this is kinda the opposite problem every1 has been having.

Background Info:
Just for some background info I just bought a MP40 full size about a month ago. I've only put 100 rounds through it; no failures to feed or failure to fire so the gun will fire correctly.

Problem:
I do have one problem/question. My magazines will not drop free when the slide is locked back and there is ammunition in the magazine (it will drop free if it is empty). Now I can pull the magagzine out on my own, but I was wondering if this was a built in feature or I need to send my gun back to Smith and Wesson. I can think of anything that would cause this problem. Does anyone know a quick fix for this? Is this actually a feature on the gun? I haven't been any info on it yet any info would help thanks.
 

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More than one mag, or just one of your mags? Do the mags fall free empty and with certain amounts of ammo, or anywhere from one round to full they stick?
 

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1st of all, welcome to the forum from Texas! 2nd, I haven't had that problem or hadn't noticed it. I usually shoot my mags empty, but I'll bet you get an answer! :yes
 

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Discussion Starter #4
Thank you for the welcome TX!! Glad I found the forum.

It happens with all three of my mags and it will happen as long as I have 1 round in the magazine. I have tried to see if it would act any different with a empty, full, half full and no difference, it just wont fall free. So this isn't a feature? Does you magazine drop free loaded with the slide locked back? Thanks for he help!
 

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Your bullets are getting hung up on the feed ramp. Not very common, but it does happen, more frequently on 9mm reloads though.

Probably want to give S&W a call on that one (1-800-331-0852), or at least a gunsmith that does work specifically on M&P pistols (Burwell, Cyrwus, Bowie, ect).
 

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Discussion Starter #6
I checked that after you mentioned it and from what I see there is still some space between front of the rounds and the feed ramp. Thanks for the advice though I think im going to have to call S&W on this one
 

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I checked that after you mentioned it and from what I see there is still some space between front of the rounds and the feed ramp. Thanks for the advice though I think im going to have to call S&W on this one
Did you check position of the round after shooting or did you just insert a loaded magazine to check clearance? Is there a possibility the last round is being pushed forward under recoil when the gun is fired then hanging up on the ramp?

What ammo are you using and what is it's overall length.

If you are manualy locking the slide back with ammo remaining you may, if not very positive in locking it open, be causing the remaining round to push forward a bit resulting in the problem.
 

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Discussion Starter #8
Did you check position of the round after shooting or did you just insert a loaded magazine to check clearance? Is there a possibility the last round is being pushed forward under recoil when the gun is fired then hanging up on the ramp?

What ammo are you using and what is it's overall length.

If you are manualy locking the slide back with ammo remaining you may, if not very positive in locking it open, be causing the remaining round to push forward a bit resulting in the problem.
Nope im just talking about not even firing it. I just cleaned and oiled the gun. Then I insert a magazine pulled back and locked the slide. So i can visibly see the round. Then I hit the mag release and nothing... I have to pull on it a bit (or tap the top of gun) for it to fall free. It really is odd, the magazine will fall free if I release and close the slide but not while its open. Just for the info I am using Winchester PDX1 defender 165 grain .40 cal ammunition in the magazine.
 

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FYI

Just checked mine when I spotted this post. FS 40. My fully loaded 15 round mag does drop out freely with slide locked back. Using Federal Guard dog Home defense rounds 135 gr. Also new and about 100 rounds through it.
 

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You are welcome. I'm a newbie, so I'm trying to pay back some of the help I have had already.:eek:n2long:
 

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Try locking the slide back without a mag in place then try inserting and removing a partialy or fully loaded mag then an empty one and let us know what happens.

Try to detect a point of lockup if it does.
 

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Hello all, newbie here as well. (Just picked up my M&P40 yesterday, haven't even shot it yet). I too have noticed the same issue and I am also located in CA. I suspect it might have something to do with our magazine disconnect since those out of CA don't seem to have the same issue. This is just my guess based on the info in this thread so take it for what its worth haha
 

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Odd. Perhaps in the empty mag, the follower is pushing up enough on the slide stop to push the mag free, but with a round in the mag, the disconnect or something else has enough friction to grip it?
 

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O.P., you wouldn't happen to have an FDE (tan) frame would you.
 

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Well, I got two new 10 round mags from Midway today and I can now say this is a mag problem.

With the slide closed, both new mags drop free, empty or loaded. With the slide open, one will drop free with 9 or less rounds, the other with 6 or less. More than that and it appears that the body of the mag is bulging slightly, causing them to stick. I will try to figure out where and either relieve the high point in the magwell, or put the mags in a vice to reshape them a bit.

The good news is both new mags easily hold 10 rounds and have enough slack to be seated with the slide closed without major effort. No need for follower mods or spring clipping on this batch.

Edit: I should add, these stick in a non-mag safety FS 40.
 

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Those of us living in free states have little to no experience with 10 round mags except for 45's. About all we can do for you is offer our condolences.
 

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I checked my FS 40 today after reading this thread. My CA compliant 10 rd magazines as well fail to drop freely when loaded with the slide open or closed. They can easily be removed by hand and drop freely when unloaded. It appears that the magazine is bulging with a full load and rubbing against the sides of the magwell. I was going to measure the size of the bulge but the battery died in my digital calipers and I didn't have a spare on me :rant:. I made a quick go-no go gauge out of the calipers and there is definitely a bulge in a loaded magazine. I tried it with both snap caps and Federal 165 gn FMJ. Both of my factory mags that came with the gun did this. Feeding doesn't seem to be an issue. Is this something that S&W customer service would handle?
 

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The question is, would they even consider it a flaw? So far mine all drop empty (they better) and they drop partially filled with the slide closed (something you do often enough in competition). If it wasn't for this thread, I don't know how long it would have taken me to even realize there was an issue since I wouldn't normally lock the slide back on a loaded mag before dropping it.

If yours don't drop with the slide closed, it could be worth a phone call to see what they say.
 
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