Has anybody ever heard of Markwell Arms? they have an address listed as being on 2414 W Devon chicago Ill, any how I am wondering if any of you would know what you would use as a proof load, this gun is stamped .45 but it is bored at.50. this is a kit gun that i picked up at a flea market it was not put together. the gun was made in Spain any thoughts would be appreciated. Thanks In Advance checker.