I have Ackley improved rifles in 4 different calibers. Head space can be a serious problem relating to over pressure. Other then my latest 280 ai which is reamed to the new nosler sammi specs. The reamers are based on the gun Smith's specs for the reamer. When I fire form my brass I use trail boss powder for the initial fire form and then a light load for the second load. This ensures the best case forming to the chamber eliminating head space problems