I just discovered a potential problem with both of my 9mm S&W M&P pistols - an M&P 9 fullsize and an M&P 9c compact pistol.

I normally leave a snap-cap in the chamber of those two pistols, since they have the old-style firing pins which are subject to breakage if dry-fired without a snap-cap in place. (Happened to me once on the M&P 9).

Well, this evening I was starting to practice some loading and clearance drills with the fullsize. Normally, I use dummy ammo for this -- cases that have been sized, but not decapped, and a bullet seated to correct OAL and no powder in the case. However, this evening, I was lazy and grabbed some snap-caps, which were at the moment handier than the dummy ammo. The snap caps are the type with a clear red plastic body (.40s are blue) and a brass base. There is a movable piece where the primer goes, and you can see through the red case and see the spring inside the snap-cap that the "primer" area pushes against when the firing pin hits it.

Lo and behold, my M&P wouldn't extract/eject the snap-caps when I racked the slide, regardless of whether I racked it medium speed or very quickly. The slide locked back (mag was empty) and the snap-cap was left lying with its rear end on top of the magazine and its nose still in the chamber. I tried it with several snap-caps, some used and some brand new. I tried different racking speeds. All with the same result - no extraction/ejection of the snap-cap.
My first thought was that I possible had a broken/worn part in the pistol. So I got out my M&P 9c compact and tried it. Same exact thing.

So I then tried my carry ammo, which is 9mm PowerBall. It performed perfectly, extracting/ejecting properly in both the M&P 9 and the M&P 9c. Distance it flew was proportion to slide racking speed. I then tried a bunch of different live ammo, including: PMC (Korean) FMJ, Win FMJ, Win JHP, and my reloads using various brand cases. All of the live ammo functioned properly, as did my dummy ammo, in both guns.
So, while the "real" ammo seems to function properly, the snap-caps don't extract/eject in either of my M&P pistols.

I then tried the snap-caps in two of my 9mm Glock pistols - a G19 and a G26. The snap-caps extracted/ejected fine in both of them.

I examined the bases of the snap-caps. I didn't use a mircometer, but the diameter of the base of the snap-caps appeaars to be the same as the diameter of the base of my carry ammo. The only difference is that the rim thickness of the snap-caps appears to be thinner than the rim thickness of any of my "real" ammo.

Any ideal? Thanks,

Bob

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NRA, IACP, INEOA, MCRGO