2"= 63.5mm; 2 9/16" = 65.09; 2 5/8" = 66.68"; 2 3/4" = 69.85mm
As long as the gun has a forcing cone of at least 3/8" rather than a Step there should be no problem shooting 67mm shells as long as the pressure is proper for the gun. Do not shoot shells loaded to higher pressures than the gun was designed for, regardless of the length.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra