Try contacting Briley. I have a Briley straight rifled turkey trauma choke tube in my 2 3/4" 12ga Ithaca M37. It turned this gun into a true 40 yard gun with remington 1 5/8oz #5. The previous best with a win-choke extra-full and winchester 1 5/8oz #5 was solid 35 yard patterns. The straight rifled seems to have improved all loads tried . The remingtons just pattern slighty better.