H335/150gr bullets/M&P10 ???

[LDBennett]

I own this M&P10, a FAL, and a PTR91, all 308. My load in the FAL and PTR91 work great. Can I expect this load to operate the M&P10? I'm using a 150 gr bullet and 41.0 grs of H335 which is a mid power level load. The brass is prepared Lake City Mil Surp.

I worry about to much gas pressure that will beat up the gun and too little gas which may not operate the gun. I have yet to find the time and weather to be able to test it myself. I am most worried about too much gas pressure.

Another limitation is that I want to stay with H335 as it is a spherical powder that meters well through my Dillon RL550B powder measure. Extruded powders do not meter well for me. H335 is an acceptable powder for use in gas guns according to reloading data I have seen published and the FAL and PTR91 have no trouble with it nor do either of my two Garands.

Any one got some experience with 41.0 grs/H335/150 gr bullets in LC brass in the S&W M&P10?

LDBennett

 

[MichiganScott]

I've used H335 in my Garands and found that it is actually on the fast side and I have to load it close to max for adequate functioning. The problem with gas guns and faster powders is that they short stroke.

Don't be concerned. The .308 AR's have problems with opening early before pressure drops during the cycle with regular loads. I'd bet the faster powders may actually function quite well at midrange levels.

 

[LDBennett]

Hmmmm..............The above reloads that work fine in my FAL an PTR91 don't particularly like my M&P10 for accuracy. 100 yard groups are not all that good. They ought to be better with the mounted 3 to 9 scope! They are poor enough to consider just putting a red dot on the gun and call it a short range shooter.

Guess I'll have to do some load development. I was hoping to be able to use one reload for all three guns (FAL, PTR91, and the M&P10). Maybe not. Darn.

I'll have to review my reloading notes to see how I got to the reload combo I have. And my eyes were giving me fits today. I think I need to see an eye doctor as my right eye has gotten funny in the last couple years. Getting old is getting in the way of my shooting!

Anyway the gun operated flawlessly. I used the S&W mag and two Magpul plastic mags. The Magpuls are superior for insertion and removal. But more work is necessary for better accuracy. These guns are not know for bad accuracy but the opposite.

LDBennett

 

[wpriest]

Just got back from the range--40.5 gr of H335 with 150 FMJ shot better than the 41 & 41.5 grain selections. Used a standard (non-mag) winchester primer. No issues-no FTE, short cycling or FTF. Used a Magpul mag.
Willy

 

[wpriest]

Just got back from the range--40.5 gr of H335 with 150 FMJ shot better than the 41 & 41.5 grain selections. Used a standard (non-mag) winchester primer. No issues-no FTE, short cycling or FTF. Used a Magpul mag.
Willy

Chronographed the loads-- 40.5 gr w/ 150 FMJ 2551 fps (avg);
42.0 gr 2754 fps (avg) out of M&P 10

Same loads in M1A about 150-200 fps faster.