The width of these receivers is the same, at 1.3 inches, but as you would expect, the M56 is longer in order to accommodate the magnum cartridges. The quarter-inch the M56 has on the M52 long-action is an expensive bit of material. The base cost of the M56 rifles is about $1,000 more than those built on the M54 or M52. The rifle I tested--a Jackson Game Rifle in .300 Win. Mag.--carries a price tag just south of $3,000, serious money by any measure.