I am trying to find out the differences between the 311, the 311C and the 311D. I just bought a 311C which was on the rack next to a 311, and 311D, The 311C was a much heavier gun with thicker barrels, even though they were the same length. I am wondering if it was originally a longer cut and the barrels were cut down to 28". The barrels on the 311C are farther apart at the muzzle than the other two guns. Is there a resource that describes the various models of the 311 doubles?