Reloading for a 308 Gas Gun

[HK Dave]

Howdy folks... going to start working up a load for my Larue OBR with 18" barrel.

I've got 175 smk and 168 smk for projectiles. I'm using either Reloader 15 or Varget for Powder.

I've read that people run less powder in gas guns than bolt actions.

Can someone explain why?

[FMJBT]

Howdy folks... going to start working up a load for my Larue OBR with 18" barrel.

I've got 175 smk and 168 smk for projectiles. I'm using either Reloader 15 or Varget for Powder.

I've read that people run less powder in gas guns than bolt actions.

Can someone explain why?

It has to do with how the brass is sized. The full length sizing required for functioning in a semi auto means the brass will expand more inside the chamber than a neck sized case will in a bolt gun. The guys running really hot loads in bolt rifles are typically just neck sizing their brass. Most bolt action rifles will also contain a catstrophic failure more safely than semi autos, so the confidence factor is a bit higher when running hot loads. FWIW, I full length size for both. For the sake of having a somewhat standardized load for all my rifles, I tailor my reloads for best performance out of the semi autos.

[FLIGHT762]

Just the nature of the beast. Gas port pressure due to propellant speed, bolt/carrier weight and buffer weight can effect the timing of the unlocking of the bolt. An adjustable gas block can help this.

I've found powders in the burning rate of 4064/Varget, RE-15, 4895, AR Comp, 8208 XBR etc. to be good. In ball powders, nothing slower than BLC-2, H335 or so, not Winchester 760, it's closer to IMR 4350, which is too slow.

In my rifle (a first production run SR-25), I have to drop powder charges about 2 or so grains compared to my bolt gun loads or my gun will beat the brass to smithereens. Galling and most importantly, it will enlarge the primer pocket and ruin the brass in one firing if I'm not careful. Different brass types will help. I've found Federal to be the worst. Remington is some of the best. I only get about 4-5 firings and then toss the brass. Some newer gas guns can run a littler better than my gun.

I can still get acceptable velocities, but nothing like I can get from the bolt rifles.

[HK Dave]

Hmm I wonder if the Larue gas selector would work for something like this... it seems to be just an on off suppressed switch.

[micro911]

I use 42 grains of IMR 4064 for both 168s and 175s in my M-1A, and have never had a problem.

For gas guns, I full length size, and use the brass for 5 - 8 times max. For bolt guns, I neck size and I use the brass more than gas guns.

[FMJBT]

Hmm I wonder if the Larue gas selector would work for something like this... it seems to be just an on off suppressed switch.

Whats the OD on the barrel where the gas block sits on the OBR? For .750 barrels, the SLR Rifleworks adjustable block would be one of the better options available. It has a detent adjustment screw that adjusts from the front like the Syrac adjustable block, but doesn't require a second tool and 3 hands to depress a tiny plunger to adjust:

[highpower790]

varget works great in m14.i load 40gr with a 168 for 2 and 300 yds and 42-43gr with a 175 for 600-1000yds.i dont know about your rifle,but a good 168 will shoot great out of anything i suspect.try the speer 125 tnt,feels like an a r.also varget is temperature stable,becareful with ball powder as groups will open up above70degrees.