I was told by an AyA customer service rep some years ago when identifying my M53E gun that the M56 and M53 were essentially the same gun, with the M56 their full scale gun designed particularly for the rigors of competitiion, and the M53 a 90% or so scaled version for field duty, purposely scaled down to save weight and make for livelier handling. They consider both as "top of the line" guns.