My Husqvarna Model 610 (hammerless) in 12 gauage is from 1948(?) and is stamped 12 - 18.5 which I think (?) indicates 2-3/4" chambers. It appears to me to be a "Sauer-like" action with swedish steel barels.

It chambers and fires 2-3/4" standard American ammo, with no problems.

JERRY