Recently joined the forum, looked but did not see an answer to this question. Is Winchester Super X .22 WIN MAG 40 grain 1910fps going to function in the M&P 15-22. I called S&W, they say yes, but the size is bigger than usual 22lr.

If your talking about these: 65132 - Ammo .22 Magnum Winchester Super-X Jacketed Hollow Point 40 Grain 1910 fps 50 Round Box,
then h*** no!:eek: they would never fit in the mags or chamber.
The M&P15-22 shoots the .22lr like
7-AX22LR - .22 LR Winchester Super-X 40 Grain LRN 1255 fps 50 Round Box X22LR
these:2-FEAM22 - .22 LR Federal Champion Target AutoMatch 40 Grain Solid 1200 fps 325 Round Box AM22
7-A0021 - Ammo .22 Long Rifle High Speed Blazer Lead Round Nose 40 Grain 1235 fps 50 Round Box
7-A22LR555HP - .22 LR Winchester 36 Grain PHP 1280 fps 555 Round Pack 22LR555HP

All of these have shot fine in my 15-22. Can't go wrong with just about any CCI products. Just make sure it has at least 1250 fps and it should cycle fine.

Thanks. I guess the customer service rep at the 800 number was going to lunch and in a hurry. I gave him the same info. appreciate your reply.

No problem and by the way, welcome to the forum.

I've had no function problems in my 15-22 even using some ammo on the 'do not use' list in the manual (had to see...)

The CCI stingers are the most accurate, solid nose (gonna try HP too). My 11 year old is getting 1.2" groups prone, no sling, 6X scope at 50 yards with them.

Where are you finding CCI Stinger solid nose?

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CSM, U S Army(Ret) 1963-1990

I like the CCI tactical. You can get a box of 375 for about $24. Not the cheapest but seems to shoot pretty clean (for a .22 round anyway) and I have had only one FTE with well over 2000 rnds done the pipe. If you stick with what is recommend in the mannual and stock up when on sale you should be fine.