The frame shown is cut for use with a Clark/Para ramped barrel. Even ball ammo will not feed if used with the barrel shown on the frame. Rock Island Armory uses a Clark/Para ramped barrel in all calibers except 45 ACP, at least in 5” pistols. Not at a bad price either for the calibers they make them for. Finding a Clark ramped barrel in 45 ACP may not be that inexpensive since the majority of barrels made are the nonramped variety.
I stand corrected. This is the right answer.