Recently scored one of the new Steyr USA 24” LMG barrels and having a hard time finding the twist rate.  I would like to fire heavier bullets in the 70 grain weight but been told I need a 1/7 twist rate to effectively stabilize it.  TIA.

70gr will work with both 1/9 and 1/7 twist.

As for the LMG barrel the Austrian made ones were 1/7… the US made should be 1/9 IIRC but I’m not an expert

Probably 1:9 like all the others unless they are imported. My 1:9 16" barrel shoots 77gr great. Cant explain it though. Maybe it's a 1:8.5 twist, maybe some weird Florida atmospheric influence...

There are 70gr bullets that can’t be fired through 8 twists let alone 9.

I’m specifically wanting to shoot the TSX 70 grain ammo which has a longer OAL than Federal 77 grain GMM.

The default twist rate for AUG 5.56 barrels has always been 1/9 from the beginning.

The US made 24" barrels are definitely all 1/9.

It sounds like you might already know this so for others: Keep in mind that it is length not weight that determines the necessary twist rate. It just so happens to be that since the diameter is a fixed value if you have the same material heavier also means longer.

Steyr barrels are famous for successfully stabilizing heavy for twist projectiles. With the extra velocity of the 24" BBL there is no guarantee but an excellent chance that it may stabilize already anyways. Try it and see.

There are only 3 5.56 AUG barrels Steyr has ever offered with a 1/7 twist.

13.8" Austrian Commando barrel. The reason for the 1/7 twist was to ensure stabilization from the short barrel no matter the extreme cold and/or altitude (think Austrian Alps mountains). There are only between 40 to 80 in the US. Most are marked with a 7 but some were not. BEWARE there are more fakes than reals! There are some specific things to look for to make sure it is authentic including a proprietary check nut a different flash hider with no grenade ring, etc.

24" Austrian original LMG barrel. The reason for the 1/7 twist rate was for tracers in the LMG OR SAW role. There are only around 200 in the US.

16" US made by special commission from PJ aka Pete Athens. There are about 200. There were 2 limited runs. One run was marked with a 7 but the other run was not. The reason for the 1/7 twist rate on these was specifically for heavy for caliber civilian ammo.

If you really just have to have a 24" Austrian original barrel with bipod and LMG brake I might be talked out of one. I have 3.

BTW for better accuracy try removing the factory bipod.

You are a wealth of knowledge.  Thank you sir!