A query to the guys who are feeding both, an AR10 and a M1A/14. Can you run the same .308 ammo in both? I’m curious about ammo compatibility between the two platforms. I understand that each rifle is unique and a load that is a tack driver in one may not be doodly in another rifle. But in general are you finding that you need a hotter load for one semi than the other? A heavier bullet? Etc. I’ve begun building loads for my Seekins AR in 300blkout in preparation for my Ruger mini 300blkout T20 garand build completion. I’m sure that there will be a difference in loads with the gas systems being so different on the rifles but just curious about what you’ve found reloading for the AR and garand/ruger platforms.

It would be difficult to extrapolate vis a vis data on a non-standard cartridge, in non standard rifles.
What I can say, is that the M1A/M14, and the AR10/SR25/M110 are designed to operate on the following: M80 ball, and it's derivatives, M852 special ball, and M118LR, and it's derivatives.

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The M1A/M14/M1 Garand is all about port pressure at the gas block.

These guns above need faster burning powders/ammo in the .308 Win burn rate range to allow the gas port pressure to drop low enough to safely cycle the action to the proper amount.

For 7.62 NATO, that is why those making this ammo stick to the wc748, h4895, imr4064 range of powders.

It has to work 100% with a wide range of rifles that are built to function with NATO spec ammo in their gas systems.

In short, for gas guns that can tolerate slower burning powders, use what ammo you want in .308 Win except in short barrel situations (less than 20 inches).

For shorter barrels, one should avoid certain powders that burn too slowly. One would do a lot of wear on a AR10 with a 16 inch barrel shooting slow burning Hornady super performance .308 Win ammo without adjusting the gas port down alot.

For the listed above firearms (m1a/m14/M1 Garand), use ammo loaded to military specifications for that rifle to avoid damage.

You can't know if some off the shelf .308 Win ammo is safe with your M1A gas system or not unless it discloses that info.

If you reload, you are looking for reloading data for service rifle, not standard data.

Hornady I believe does have a section in one of their manual revisions for .308 Service rifle load data.

Interestingly enough, Hodgdon recommends CFE223 for .308 Winchester, but specifically NOT for 7.62x51MM out of a gas gun, even though it and BLC(2) are next to each other on burn charts, and the scuttlebutt is that CFE223 IS BLC(2) with a decoppering agent(bismuth) added to it.
You can't make this stuff up.
I inquired with Ron Reiber at hodgdon(indirectly so), and he said CFE223 was not recommended for 7.62 NATO in a gas gun.
Go figure. But BLC(2) is, as it is generally accepted that WC846 and BLC(2) are more or less the same powders, although WC-846 is the non-cannister version, w/ flash retardant.

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I can attest to WC846, at least the lot I have burns faster than BLC-2, it is very close to Winchester 748 in burn rate.

Other than the amount of powder is different to achieve the same velocity/pressure, they print nearly the same groups and average velocity for my M80 ball reloads.

Speaking for the AR 10 platform. My RRA LAR8 chambered in 7.62 and a mid length gas system, eats everything, NATO, MSR hunting rounds.

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Appreciate the input guys. Looks like it will be trial and error with the bullet, powder and recoil springs as the variables on the ruger. I shouldn’t have the op rod issues that the M1 has as the 300 is alot less juice but I’ll still have to pick the correct powder. My smith has the bbl done for the gas cylinder and should have the op rods done next month. Then we can do some ammo testing to see what works. Currently I’m building loads for my AR in 300blkout. Starting light and working up.

You're doing load development for Ruger Mini 14 300 blackout?

If so, then it is a whole different discussion although some of the accuracy culprits of the gas system causing point of impact shifts are exaggerated with 300 blackout in Ruger Mini 14.

I have never shot a single round of factory ammo out of mine.

Cold bore shots depending on the quality of ammo has yielded me anywhere from 2 MOA to 4 MOA from the center where most shots land.

That might be my rifle being a lemon, haven't gotten around to wanting to put factory match ammo.

I should be able to squeeze out consistent 1.5 ish MOA 3 shot groups using match bullets with at least one powder, but to no avail.

Regarding blackout ammo, you can run as heavy pills as the 1/7 twist will allow.

Powders, any of the blackout powders will work in making the bullet go "pew".

The issue is gas port pressure for subs. Use the slowest burning blackout powder.

CFE BLK powder will cycle 200gr or 220gr subs in the Ruger Mini without a suppresor.

I don't plan on shooting any more subs, so I'm going to replace gas port bushing to smaller and op rod bushing and see if I can get more consistently better accuracy.

If it is still a turd on accuracy, I'll probably buy a box of factory match, test it, and if it fails I'll sell it for a Ruger American ranch AR mag in 300 blackout or possible get out of blackout and stick with 7.62x39.

To clarify, I’m doing load development using my AR 300blkout for my Ruger mini14 build that’s been rebarreled to 300blkout and will hopefully be reconfigured into a T20 Garand using the Garand’s gas cylinder/op rod gas system instead of the ruger’s gas block system. I understand that it’s apples to oranges which is why I asked what I did initially hoping that another shooter might have an AR and a M1a that could be somewhat compared to each other ammowise. Supersonic ammo only, no subs.

Usually, this type of weapon and ammunition requires faster gunpowder.