1:10 twist. I have tried h335, tac, imr4064, exterminator, imr4350 and I think it was h380. I ladder tested .5 from mid to max loads. He set the chamber for the 168s I had loaded. With the 168s, it shoots about 1/2 moa or better. I need to just order another thousand 168s now that they are back in stock.