Does anybody knows what M stands for below? Glock Barrel M/32 357 Sig Item: GLO-8665 Ample Stock Manufacturer: Glock Inc. $150.95 Product Info Specs Genuine OEM Glock replacement barrel. Barrel rifling has hexagonal profile with right hand twist. 4.02 inch - 102mm length. Fits M/23,27,32,33. Part number 15 on the Glock Schematic.