155s and H4895 in 308 gas guns

[jlorenzo]

What are some of your loads using this combo? I have Hornady 155 bthps, Sierra 2155 and 2156 155 smks and the best group my gun has shot was with the Berger 155.5 full bores and 42.8gr of 4895, 2.800 COAL. I am using Starline small primer match brass and Federal Gold Medal match AR primers.

For whatever reason neither of the Sierra bullets have shot very good so far. Just looking for data points to compare against my own.

Everything I've tried so far has been loaded at mag length. I have a Krieger 20" M110 barrel, 10 twist. JP high pressure bolt and SA adjustable gas block.

Is 2750 a realistic velocity goal with this setup and 155s? So far have only reached the high 2600s.

 

[kevinbritvec]

IMO, 2750 fps is fine for a 24" bolt gun, for a 20" gas gun, not so much. I used to get 2725 to 2750 fps with 150 grain bullets through my 22" M1-A barrels using Lake City brass. That would equal somewhere close to 2700 fps from a 20".

My .308 gas guns run best and group best using service rifle loads:

168 grain SMK's - Lake City or IMI brass
40.0 grains of IMR-4895
40.5 grains of IMR-4064
43.0 grains of WW-748
40.5 grains of AA-2460
41.5 grains of VihtaVuori N150

I don't worry about velocity. These loads run around 2500 fps from a 22" M1-A and work great.

My 155 grain loads are only a little higher and run around 2600 from a 22" barrel, that would average around 2550 from your 20" tube. Safety first, reliability second and tight groups last. In that order. You really want a 3:00 o'clock ejection pattern from an AR-10.

 

[SecondsCount]

The 155 SMK shoots really well in my Tikka Master Sporter, usually in the .5s