Home Forums Reloading Big Game Rifles Sub sonic 308 load?

A friend ask me to help him find a recipe for a 308 sub sonic load . Trying to duplicate a load from Atomic that Midway sells. It lists a 175 grain bullet at 1050 fps. Those cost $1.15 per round.

Any ideas or info appreciated. Thanks.

What twist rate? That'll determine how heavy/long you can go with the bullet choices. What you're looking to do is very attainable, and something I do a lot since I like to shoot suppressed subsonic rounds.

A point that might save you a lot of headache - in rifle cartridges of this size (and larger), cast bullets are a lot easier to develop a good subsonic load for than jacketed bullets. Jacketed bullets in very low pressure loads and high volume cases like this can be picky and exhibit really high ES, as well as having much higher danger of sticking a bullet in the bore. If you do use a jacketed bullet, try to pick something with a very thin jacket, meaning a match bullet like a Berger VLD, Hornady BTHP, etc. Don't worry too much about ballistic coefficient values though; it doesn't matter nearly as much in subsonic loads.

If you proceed with cast bullets (preferably powder coated!), most of the fast pistol powders like Bullseye, Red Dot, Trail Boss, etc work pretty well and are easy to find a load for. I don't mention actual charge weights because in my experience it can vary a lot; one rifle might want 5 gr while another in the same chambering might take 6.5 gr to get the same velocity. Shoot for ~900-1,000 fps, faster than that (and especially above 1,050 fps) is technically still subsonic, but is noticeably louder as velocity increases up to the supersonic range.

Just remember to work the charge down to subsonic level, not up; you aren't worried about the load being too hot, but you don't want to start too low and stick a bullet in the bore.

Hope that helps!

Thanks for the info. I found a lot of info on Hodgdon's website on Trail Boss reduced loads. His rifle is 1-12 twist but he says it groups the Atomic 175 load well. I suggested a 170 flat nose. Up to 100 yards, there isn't much difference in trajectory or velocity, plus it's a shorter bullet.

Trailboss is what you want. We were around 10-11 grains with a 208 amax.

Yes, a 170-180gr flat nose would be a great choice there. I don't buy cast bullets since I make my own, but you may be able to find some powder coated commercial cast bullets in that range that would work really well.

Trail Boss is one good choice, but don't assume it's the best powder; you'll want to try a few different powders for your rifle, and don't be afraid of some dacron or cotton ball filler if needed. In some cases TB gives pretty high ES that is too much to be acceptable.

I use a 170 Partition 30-30 bullet. 10 grains Trailboss. It will punch right through pigs at 50 yds. Here’s some we shot with suppressed loads. My favorite pig picture!

Is that with a 308 and what's the velocity?

Look in Hodgon's annual manual Win 308 subsonic 8.0 grains TiteGroup stuff I use a 168 gr Sierra HPBT in my 15" encore one hole at 25 yards haven't had the time or weather to try any longer but I think other than drop I found my best load !, I do some other stuff to insure perfect ignition though, since its not in the manual I'll PM it to you. haven't chrono graphed it and don't care, Hodgon manual states 1080 with a 24" barrel

I'd be reaching for Unique or Red Dot...myself....