Yeah...i knew that already, but i meant more in terms of the stated size. Eg: a 30caliber rifle could be a 30.06, .308, 30.30,....etc..that kind of deal. So a kit requiring a .40 engine, could use .40 or .46 etc...right..? Or am i completely off still?[] Oh well..as long as you guys say i can use a .46 in my MKII, i will. Theres so much to learn, so little brain space to learn it all. Hehe. Well, once again, thanks for all info. Peace---Nathaniel