I bought a brand new M&P40 Pro Series with the 5-inch barrel, and fiber optic sights, and finally took it out shooting today.
The first rounds I fired out of it were some 3 year old Federal 135g RHT Frangible rounds. I had multiple failures to return to battery with this ammo.....around 5-6 out of 50 rounds.
I then fired 50 rounds of Federal 180g HST JHP, and had no issues, followed by 50 rounds of Winchester Ranger-T 180g JHP, again, with no issues.
Fluke, or something to worry about?
I wonder if this particular M&P just hated the Frangible rounds?

Originally Posted By Mach:
frangible rounds are known to be very lightly loaded.
My H&K USPc .40 ( only gun I ever shoot frangible with, requal required ) fails to return to battery after about 150 rounds of frangible. It's the light loaded ammo combined with a not-so oiled (or greased ) gun and some carbon build up.
If it functions with standard FMJ or carry ammo, I wouldn't give it a second thought.
Well, the other 100 rounds were JHP, and they fed and functioned fine......meh. Fluke I guess....
Probably not enough grunt to run a brand new gun but it could also be overall cartridge length.
I reloaded some 155 grain bullets slightly short and would get failures to feed about once or twice per mag in my M&P40 FS. The next batch I loaded .020" longer and they run 100%