I know the rules.
You might want to re-read them yourself............since there is a handgun cartridge spec.
1.16" min case length...........and .243 min bullet dia.
Not all rifle cartridges fit that spec.
Some may fit the spec but are called out specifically as a "no go".......example: 30 carbine (there are others).
FWIW I prefer wheelguns (iron sighted) for handgunning deer.
I don't know what the hell i was thinking... Duh... Now an AR in .450 Marlin! Yeah... I wonder if it would be possible with a belted case?44 Rem mag is rimmed case, proly have to go .44 automag.