I do not know of any drums for the 5.45. The noise level on the shorter barrel is considerable compared to the longer barrel, I am not sure about the short 7.62 vs the 5.45. The recoil on the 5.45 seemed like a 22, its so controllable to me. The question of caliber was easy in my mind. The bulgarian krink was really built as a 5.45 gun, I could not see building one in 7.62 or 5.56. they just dont seem natural. On the other hand many people just love the other calibers, so its a matter of building what you think you want.