M&P 40c extended magazine does not drop

[archerross]

I just purchased my first S&W last week and today joined the S&W Forum. I immediately gave my new carry piece a good cleaning before heading to the range. I noticed that after the final shot from the extended mag, and the slide still retracted, the magazine will not drop reliably. It will disengage, moving approx. 1/8 in., and stop. If the action is closed, the ext. magazine will drop perfectly. I returned home, gave the ext. mag and mag well a wipe down and light lubrication, but it still does not function properly. I can reproduced this at home simply by locking back the slide. About 75% of the time the ext. mag will not drop. The flush magazine works perfectly.

Has anyone else had this issue? Is there a reliable fix or will I need to call S&W?

[alde]

First welcome to the forum.

Does you extended magazine have a spacer to fill in the space between the bottom of the grip and the magazine base plate? If so have you tried the magazine without the spacer?

[robkarrob]

First don't oil/lube the mag or mag well. Just more ways for crud to stick to it and more likely it will hang. Especially do not lube the inside of the mag or the follower. You have figured that the slide location effects the dropping of the mag. Something has to be interfering when the slide is open. Does it happen with a cartridge or two still in the magazine? Does it happen when the mag is empty? Check the operation of the mag releasing with the slide removed. Hard to diagnose without seeing it. Could be the mag catch still holding it, but the location of the slide should have no bearing on that. Check closely for interference and advise.

Bob

[robkarrob]

Another idea. Check the followers on both mags, comparing them as to how far they are raised up. The follower exerts the pressure to "snap" the mag out. Could be the follower is either sticking or is not formed properly to contact the slide lock correctly. With the slide closed the slide lock is down, which causes it to produce more pressure on the follower. With the slide open, the slide lock is raised, which produces less pressure on the follower, less pressure to snap the mag out. If the mag only drops a little, then the pressure of the mag catch will hold the mag from fully dropping out.

Bob