I reloaded some ammo for a FRIEND'S STOCK S&W M&P 10 that got to be right interesting. I started out with a 150 FMJ bullet and a charge of IMR 4895 powder that works with a 168 BTHP in my Rem 700. This loading was done with the same jug of powder.
The initial load of 42.7 grains (I loaded 5 rounds) was too hot for the S&W. But the remaining rounds fired without any problems in the Rem 700. Ultimately, the load was reduced to 41.0 gr with 150 gr FMJ bullet. All the powder charges were hand weighed on an RCBS 510 scale. Two other combinations were also too hot. An experienced reloader at the range suggested buying a box of factory 150 gr FMJ and see if it shot ok. The factory ammo was not a problem.
On my third batch of test loads, I fired 4 rounds of factory 150 FMJ, 5 rounds of 150 gr FMJ reloads, 5 rounds of 150 gr plastic tipped bullet reloads, and 5 rounds of 125 gr HP reloads. The resulting target at 100 yards amazed me. I had four 3-shot clover leafs that were ~ 3/4" apart. The composite group size was under 2" diameter with 18 rounds. The one flyer was 150 gr FMJ that was my error.
The empty brass ejected to the same 6" circle on the range floor. The "high pressure" rounds were an eye opening experience that caught me by surprise. I never thought a mid-range load in a bolt gun, would be too hot for an AR style rifle.
Be careful folks.
The initial load of 42.7 grains (I loaded 5 rounds) was too hot for the S&W. But the remaining rounds fired without any problems in the Rem 700. Ultimately, the load was reduced to 41.0 gr with 150 gr FMJ bullet. All the powder charges were hand weighed on an RCBS 510 scale. Two other combinations were also too hot. An experienced reloader at the range suggested buying a box of factory 150 gr FMJ and see if it shot ok. The factory ammo was not a problem.
On my third batch of test loads, I fired 4 rounds of factory 150 FMJ, 5 rounds of 150 gr FMJ reloads, 5 rounds of 150 gr plastic tipped bullet reloads, and 5 rounds of 125 gr HP reloads. The resulting target at 100 yards amazed me. I had four 3-shot clover leafs that were ~ 3/4" apart. The composite group size was under 2" diameter with 18 rounds. The one flyer was 150 gr FMJ that was my error.
The empty brass ejected to the same 6" circle on the range floor. The "high pressure" rounds were an eye opening experience that caught me by surprise. I never thought a mid-range load in a bolt gun, would be too hot for an AR style rifle.
Be careful folks.
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