I had a chance finally try my new M&P 9 uninterrupted recently and noticed something and wanted to know if it's functioning correctly.

Upon emptying the first magazine, the slide stays open as it's supposed to. After dropping the empty mag and placing the second full mag in the weapon, if I slowly lock the mag in, I have to manually pull the slide back then release to chamber a round.

Here is what surprised me, if I slammed the second mag in place, the slide would automatically release and chamber the first round. Is this normal?

Yes it is.

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Science plus Art

Awesome. Thanks!

It's been discussed many times. S&W calls it normal, many people (me included) see it as abnormal due to inconsistency - pick what you like

I saw that too and thought it was odd also. I am used to a 1911.

Not sure how to answer but mine auto forwards the slide about 85% of the time my M&P 40C does not although I just got it, but it does seem that if you forcefully insert a new mag especially at about a 45 degree angle it will auto forward and you are ready to blast away!

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59,M&P9,40,40C,357,(2)45,G26

My M&P9 does this and I do not mind it at all when shooting a match. Friend has a M&P9L that will do this also but will not always pick up the next round.

Thanks for all the replies. I did try to do a thorough search prior to posting.

I don't see a latch or mechanical means for this to be intentional, however for a true M&P situation, I see where this would be a desirable function.

As long as it does this consistently, I think I'll like it. I'm pretty sure my Sigma did not do this, however I don't think I ever tried this with it. I'm practicing keeping the weapon in my sight picture and bringing the magazine up to it, and "positively" seating the magazine.

Just curious, did you read your manual thoroughly?

Why, yes, I did. There is a warning that this can happen, surely put there at the request of some scum sucking trial lawyer.

This is not just something that happens with the M&P or S&W, FWIW.

I have only put about 250 rounds through my M&P40C and usually it does not self forward, however today at the range after I had finished shooting and was replacing my hollow points into it I slammed the magazine and it auto forwarded.

My M&P9 full size auto forwards about 85% of the time but for my 40C this is a first, so this makes me wonder if it is supposed to auto forward because it is not 100% reliable!

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59,M&P9,40,40C,357,(2)45,G26

To use a metaphor, I remember hearing once that a software feature is a bug with seniority. The auto forward may seem to save a step, which could be desirable, but be ready to perform an immediate action drill if your pistol goes "click" when you were expecting a "bang."

Your cue is in the use of the word "slammed". It is neither necessary nor desireable to "slam" the magazine home. Excessive force in seating the magazine can cause a round to jump free of the feed lips, which will cause a double feed. This is not something you need to happen either in a match or during an armed confrontation.

I've seen several AR mags vomit their entire contents out the ejection port as a result of excessive force. Cracked magazine tubes caused by the excessive battering over time allowed the mags to empty, a history of excessive seating force was the root cause.

Yes, and if slamming the mag home consistently chambers the first round, it can be deemed a benefit.

Excuse me but if I am in a fight for my life I will definitely slam the magazine, I am not at the range I am in a gun fight and my purpose is to come in first place, this bug or feature could be a life saver IMO!

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59,M&P9,40,40C,357,(2)45,G26