C'mon guys. This search took every bit of 90 seconds. From the Blaser website ..........

Triplex Bore Design The extremely flat forcing cone of the F3 with an angle of 2,5 degrees, the "overbore" inner diameter of 18,65 mm (0,735") and the magnum and steel proofed caliber 12/76 (3") ensure the perfect combination of optimal muzzle velocity, homogenous shot pattern and moderate recoil.

SRH


May God bless America and those who defend her.