Ted, is correct. Just as a major ammo company developed the 3.5" 10 gauge shell in conjunction with the Ithaca 10 gauge NID over 80 years ago, Federal Ammo in 1988 developed the 12 ga. 3.5" shell for turkey and geese. The first gun chambered for this round was the Mossberg 835 Ulti-Mag pump. Other than a 12 gauge chamber, the barrel was over bored to 10 gauge. It wasn't long before other guns followed suit. Gil