I have roughly 500 rounds through the rifle and the final round in the magazine tends to stovepipe probably 30 - 40% of the time.

I have a factory 10 round short mag, and pay attention to ammo staggering, so I don't think that is the issue. It only happens on the last round.

I've tried cci and federal auto-match ammo with similar results.

Is it a defective mag, or is there something else I should check?

My guess would be the Mag Spring. It could be several other things, but a bad mag spring would be my first guess. Have you tired multiple mags?

I need to try another mag. I live in Cali and we are restricted to 10 round mags. Short mags have been tough to find at reasonable prices.

Thanks for the input.

YW, if you can't get one easy, order a spring for the mag and replace just the spring.

I'm confused, you mean the round before the last one stove pipes?

The mag should lock the bolt back on the last round, making a stove pipe impossible - sorry I must be missing something.

Doc: PM me with your address and I will send you a short ten round model that has had a little use, and works well in my rifle.

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Uva Uvam Vivendo Varia Fit

I just picked up 2 from Midway, 3 weeks ago. They weren't P-Mags and are stainless steel. Bright orange follower, hold open feature works and cost $13.99 per regular price. I scarfed them up when they were on sale for $10.99.

C Products Defense Mag AR-15 223 Remington 10-Round Orange Anti-Tilt

Those aren't for a M&P 15-22

My bad. Wrong thread!! (But they do work well!, just not in a 15/22)

Midwayusa does have some 10rd long bodies in stock. For the 15/22.

Smith & Wesson Mag S&W M&P 15-22 22 Long Rifle 10-Round Long Body

Sorry if I was confusing. The last round out of the mag stovepipes while loading. It hasnt been fired. When the last round does fire, the bolt remains open as expected. I managed to find another mag to try. Once I receive it, I'll give it a shot to see if it's the mag causing the problem.

I assume you are talking about a 22.

Drop the mag with one round in the chamber and one in the mag. This is the 'tactical' way to handle ANY mag fed semi.

Aside from how these things should be operated, you have a magazine function problem or a dirty gun.