22/45 Fan said:
The attraction of an Old Army with an after-market .45 Colt cylinder is that neither of them are ATF regulated items so there is no registration, no forms to fill out and you can order and ship them by regular mail
True if they are shipped separate. If it shoots a modern cartridge it is considered a modern handgun. In order for it to be considered an antique black powder firearm, it needs to be in its original form. Also, some states have restrictions in its original form but most states don't.