DPMS upper on M&P lower

Paints-n-cows · Mar 9, 2013

Today, a neighbor of mine and I were talking about his M&P10 that he just bought. He was looking for some magazines so I found him a few. I had not tried them in my DPMS prior to me giving them to him.

Anyway, long story short, one was a C-Products and the other ones had no name on the floorplate. They wouldn't insert into his lower and were overly snug in both of my DPMS .308s.

Out of curiousity, I tried to put my DPMS upper on his S&W lower and it would not go. The front pin would not slide all of the way through and you couldn't rotate the upper to 90 degree so I could look at it. When I tried to close the upper/lower together, it also would not go.

Since I didn't want to bugger up his brand new rifle, I didn't force the issue.

Also, I noticed that the DPMS lowers were wider than the M&P. It has very thin action walls in comparison to my lowers.

Anyone else notice this?

freedoom · Mar 11, 2013

I dont think the DPMS LR-308 takes the same magazine as the M&P 10. the M&P 10 uses SR-25 style magazines.

Paints-n-cows · Mar 11, 2013

Actually the M&P 10s do take the same magazine as my DPMS mags. That is how this whole thing got started.

Smitty357 · Mar 11, 2013

Paints-n-cows said:
Actually the M&P 10s do take the same magazine as my DPMS mags. That is how this whole thing got started.

They wouldn't insert into his lower and were overly snug in both of my DPMS .308s.

Did i miss something or did you just say 2 different things.

Vision Remodeling · Mar 11, 2013

AR style 308/7.62 rifles do not interchange uppers and lowers by brand. The DPMS/SR-25 pattern mags are being used by most. I have found that there are variations between mags that are this pattern but do not fit. I passed on a DPMS that would not accept a .308 P-Mag. I have seen other DPMS that will. I think the M&P-10 is being shipped with P-Mag. I will bet that some of the other brands will not fit properly. I went with Armalite before the M&P came out, and can only use their mags.

Paints-n-cows · Mar 12, 2013

Smitty357 said:
Did i miss something or did you just say 2 different things.

No, you didn't miss anything. I had gotten him some mags for the DPMS platform but they wouldn't fit in his mag well but would in my DPMS mag wells. Evidently, there are some dimensional differences between his M&P and my two DPMS rifles. Those 3 were C-product magazines. The actual factory DPMS mags slide right up into his mag well with no issue.

When I got home, I took a dremel tool and a sanding drum to the back narrow portion of the magazine and took off about .030" and they slide right and dropped right out of my magazine well. I suspect that the welds along the back of the mags were too thick.

His rifle shipped with a either a five or ten round magazine that was steel. I didn't really look at it very closely.

Since the mags fit, I was just surprised that the uppers wouldn't.

rojodiablo · Mar 14, 2013

Paints-n-cows said:
Since the mags fit, I was just surprised that the uppers wouldn't.

Different pin sizes? This has been an issue with a couple AR15 platforms. As to the top end not dropping in all the way, I do not know what to say without seeing them.

Vision, Armalite finally capitulated and came out with an AR10 that will accept Pmags. They rendered their proprietary setup obsolete via this, but in the end, commonality is a good thing. Not to mention, Armalite refused to play nice with Magpul and several other magazine makers in the past, and payback is a real bugger sometimes.

DPMS upper on M&P lower

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