Home Forums Reloading Big Game Rifles Loading for 18" AR10 in .308 for medium to long range shooting

My current 308 load is 44 grains of Varget under a 175SMK in a Win case. Gets me around 2675 fps in my 24" Savage bolt action and makes a ragged hole at 100 yards. I shoot steel from 300-1000 yards.

I am in process of building a suppressed 18" AR10 and would like to be able to shoot the same targets. I know 18" is not ideal for this application but its definitely possible. Can I safely shoot this same load in my new gas gun? Or will the pressure be too high?

I am told that I can expect a velocity loss of roughly 25 fps/ inch of barrel. So 6 inches = 150fps loss = let's call it 2500fps at 18". Will the 175 grain bullet still be effective at this velocity beyond 500+ yards? Would I be better off from a ballistic standpoint shooting something like a 155 grain Scenar or ELD-M at say 2650fps?

Don't get me wrong, my 5R 308 loves the 175 SMK. Per Quickload and Hodgdon (42-45) you are approaching max. I would look at the 169 SMK.

It will depend on your rifle and chamber as to what will work.

In my 18" .308 gas gun, my standard load from my Remington 700 will be slightly over-pressure. Primer pockets get loose much sooner and the ejector puts a good gouge in the brass. Occasionally, there will also be bent rimmed from the extractor. I would recommend you work up a specific load for the gas gun. For my rifle, the next node down was 0.4 gr down with Varget and a 175gr SMK.

Every rifle is a little different, so I’d work up a new load.

I’ve been shooting a Remington and a Tikka lately, both with 20” barrels. Either will do 2,700 with several 165-grain handloads. Factory 150s tend to run 2,650 to 2,700 fps and 180s tend to run 2,450 to 2,500 fps. One or two run a bit faster. Careful load work might match those speeds in an 18” barrel, but you’ll be near max. Even in a 308 that can burn up a barrel faster than you’d think.

For hunting, the Barnes factory 130-grain TTSX does right at 3,000 fps in both rifles with superb accuracy. Handloads are about 100 fps faster.

“Better off” depends on a lot of things. The 155 Scenar is an excellent bullet, but a lot of the long-range records that it holds were set in Palma matches, which prohibited anything other than 155-grain .308” bullets for decades. If I were going to shoot beyond 400 yards regularly, then I’d look at bullets with higher BCs.


Okie John