.308W reloads in AR10

BigBoreBubba · Sep 7, 2021

Charlie98 said:
It's generally considered too fast for rifle-length barrels and match-type loads, IMR4895 is considered the entry-level powder for even 150's in hunting loads. LIke BlueJay, I have found IMR3031 to be excellent in my short-barreled M1a, better even than IMR4895. I don't think IMR3031 is a good match for 168 or heavier bullets, however, but I'm sure there are exceptions to that, somewhere. It is likely you would see velocity benefits with a slower powder, like IMR4895, in a rifle barrel vs IMR3031.

I did a quick workup with H335 and the 150's as an alternate to IMR3031 or IMR4895 in my M1a (and in the .30-06 Garand...) it worked well enough, but showed pressure signs quickly (mashed primers,) and had a pretty good blast and fireball, at least compared to the IMR flavors. If you have a bunch with no other use for it, it's not terrible, but it's not my favorite, either. I think I settled on 41.5grn H335, #34 primer, in LC brass, under a 150grn Hornady FMJ for the .308. I consider that a near max load in my M1a. It gave me 2530fps, which is right around what my equivalent loads with IMR's 3031 or 4895 give me. I don't notice a difference under 300yds... but beyond that, the lower velocity of both the load and the short barrel start to take their toll.

I quit trying to match factory velocity with my M80 duplicate load... it put me too close to the edge. I'm at about 95% of factory and everything is peachy.

Just curious, what pressure signs were you getting with H335 at that charge weight? I did a ladder from 41.0 to 43.0 when I worked up my 155gr HPBT load. I didn’t have any pressure signs in that test. 43.5 was the listed max, so I stayed 0.5 under. I settled on 42.4 in the end.

Charlie98 · Sep 7, 2021

41.8grn H335 had some mashed flat primers with 145grn Prvi bullets, but not with the Hornady bullets... which was a little odd. 42grn H335 with the Hornady was OK, the primers were mashed pretty flat, however. I know that is not the only barometer of pressure, but it's an easy one to spot. These days I have to pick my battles... and leveling off at 41.5grn H335, which is what my basic IMR3031 load is, oddly enough, seemed like a win-win. Just a reminder... this was in LC brass, with less case capacity than commercial brass.

CoalCrackerAl · Sep 7, 2021

There was a guy at the club shooting a AR 10. He had to manually load every round. I asked him if he was shooting reloads. He said no just cheap federal 308's. I suggested he checks into adjusting his gas block to cycle hunting rounds. A side note that rifle was very annoying to be next too ! The range was busy so i was stuck next to him.

Ray P · Sep 7, 2021

bluejay75 said:
This data is from a 18.5 inch barrel, 150 grain Hornady Interlock. 3031 is a winner in short barrel 308. This is in LC and FC brass. Not sure how it happened but the FC gave more compression than the LC. I think the FC was SB sized. Work up carefully. This is not max but it’s close. It shot right at an inch and it was temp sensitive. In the peak of summer this load left a slight ejector mark but held its accuracy.

View attachment 1023914

Thank you, Bluejay 75!

Ray P · Sep 7, 2021

Kaldor said:
Service rifle data is for rifles that might have physical limitations on what you can run due to some mechanical portion of the rifle cant handle the added pressure. There are no limitations like this on an AR10.
As others have pointed out here, if you have an adjustable gas block properly adjusted, you can do whatever you want, is long as you dont see pressure signs elsewhere.
I only use LC brass in my AR10, and while most places say cut back about 2gr from max load, Ive actually found that 1gr is more truthful, but you need to watch for pressure signs as your rifle isnt the same as mine. I use CCI200s, Varget, CFE 223, 8208 XBR, and probably a few others for powder.
However, while I have pushed the envelope pretty hard, my standard M80 ball cloner (150 FMJ) load only hits 2800fps. Its cheap, accurate, and easy to load. I run 168s for general plinking ammo are a bit hot, but Im shooting them at 500-700 yards on a consistent basis. My hunting loads with 175s are pushing hard and I have no concerns.

Great info, Kaldor. My adjustable gas block is on order. But while I wait for its arrival I'm gonna explore service rifle loads with the powders I have on hand. Once I find a load I like at this level, I will put on the adjustable gas block and start looking into warmer loads with 168 - 180 gr bullets.

Kaldor · Sep 7, 2021

Charlie98 said:
I quit trying to match factory velocity with my M80 duplicate load... it put me too close to the edge. I'm at about 95% of factory and everything is peachy.

I was bumping just shy of 3000 fps on my first pass with my M80 ball load from a 22" Criterion barrel in my AR10 with CFE 223. I dropped back to a much safer load of 8208 XBR and its proven to be very reliable, safe in my guns, and pretty good as far a accuracy goes. Also have seen no issues with primer pockets loosening or necks cracking. Factory M80 ball is in the neighborhood of 2700-2750 fps and is 2 MOA ammo on a good day, so Im beating that by a good margin both in velocity and accuracy.

Ray P said:
Great info, Kaldor. My adjustable gas block is on order. But while I wait for its arrival I'm gonna explore service rifle loads with the powders I have on hand. Once I find a load I like at this level, I will put on the adjustable gas block and start looking into warmer loads with 168 - 180 gr bullets.

The trick to setting a gas block so you can set it and forget it is to choose the heaviest load you plan on shooting as it will generally have the lowest port pressure. For example a 150gr load will generally use more powder than a 175gr load, thus the 175 will have a lower port pressure. Obviously, there are some exceptions to that rule, but its a place to start. Each manufacturer has their own setup instructions, but generally you can start in the middle of the adjustment range to get the gun to run and just tune it down until the gun doesnt lock back on an empty mag, and then go up one or two clicks for a bit more gas. Sometimes you may need to open it up, so just open until it locks on an empty mag. I have 4 Superlative Arms blocks, and they are fantastic.

BigBoreBubba · Sep 7, 2021

Charlie98 said:
41.8grn H335 had some mashed flat primers with 145grn Prvi bullets, but not with the Hornady bullets... which was a little odd. 42grn H335 with the Hornady was OK, the primers were mashed pretty flat, however. I know that is not the only barometer of pressure, but it's an easy one to spot. These days I have to pick my battles... and leveling off at 41.5grn H335, which is what my basic IMR3031 load is, oddly enough, seemed like a win-win. Just a reminder... this was in LC brass, with less case capacity than commercial brass.

Just thought I’d put this out there. That’s actually 4 shots. That’s the best group I’ve ever shot with that gun.

Ray P · Sep 7, 2021

Kaldor said:
the trick to setting a gas block so you can set it and forget it is to choose the heaviest load you plan on shooting as it will generally have the lowest port pressure. For example a 150gr load will generally use more powder than a 175gr load, thus the 175 will have a lower port pressure. Obviously, there are some exceptions to that rule, but its a place to start. Each manufacturer has their own setup instructions, but generally you can start in the middle of the adjustment range to get the gun to run and just tune it down until the gun doesnt lock back on an empty mag, and then go up one or two clicks for a bit more gas. Sometimes you may need to open it up, so just open until it locks on an empty mag. I have 4 Superlative Arms blocks, and they are fantastic.

I have installed one adjustable gas block a few years back on a carbine length 450 Bushmaster. I started with a closed port, and stopped opening it when the bolt would successfully cycle and load a new cartridge. That was really catch-as-catch-can. Your process sounds a bit more deliberate and thought out. Definitely will try it. Thank you!

IALoder · Sep 8, 2021

A little "faster" powder may be the ticket for the 150's in the shorter barrels. Accurate 2230 gives really good speed with 150's well within Western's "service rifle" data (for 155's, but close enough). 42.0gr gave no pressure signs, and 2750fps with mixed brass in my 20" AR10/LR308. Father in Law's FAL likes the load as well.

.308W reloads in AR10

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