I have a 12.5" arp barrel as well and its very accurate. I run a yhm titanium suppressor on it. I get 2420 with the hornady 120 sst and 2680 with the factory federal 90 grain xm6.8. Im getting same velocity out of my 12.5" barrel wth 120 grain sst that my dad is getting out of his 18" 300 blackout using the 110 barnes. I bought a bunch of the federal xm6.8 for 12.99 a box and its surprisingly accurate.
Wife slaying the first animal with it!
The 120 hornady sst is on left and the federal xm6.8 that uses a 90 grain speer gold dot is on the right(2 shots). Shot into water at 100 yards.