Just like to add to what Farmerbrown32 said. I have two rifles in the 223A.I. and KNOW he is telling the truth about one hole groups! What he hasn't said is what velocity increase you can get. I'm shooting a 55gr Sierra to 3600 over the chrono! And it's scary accurate. Oh, my twist rate is 14, don't know his. But that is one heckofa cartridge. Looks like he has a great rifle too at a nice price.