In a somewhat recent thread a poster stated that his 20-ga. Repro w/26" bbls. chambers measured 3" depite them being stamped 2 3/4", he mentioned that he was the original owner of the gun.
http://parkerguns.org/forums/showthread.php?t=23036
In this same thread the original poster also claimed his gun measured and stated the same, but he wasn't sure of its originality. This prompted me to measure my 20-ga. Repro with 26" bbls and measure its chamber length -- it's stamped for 2 3/4" chambers and actually measures having 2 3/4" chambers.
In an effort to become better informed, it would be interesting to know what your 20-ga. Repro w/26" bbls. chambers actually measure in length?