I have a H&R single shot 45LC Carbine with a pretty thick 18" or so barrel.  Do you think it can handle 45LC+P ammo? Loaded almost like a 454 Casull it seems.  The particular load is made by Buffalo Bore and its 325 grain coming out 1,300fps.  The barrel looks very stout. but I'm not sure if H&R uses cheap steel or not. The box of ammo says just to use it in T/C, ruger revolvers and marlin leverguns.  What do ya think? thanks

This one, however, is a different animal than the 77/44.  You might talk to H&R first, but I know I'd feel confident shooting a hot load out of my H&R Handirifle .44 Magnum.

These rifles are available in various high powered rifle calibers and the 500 S&W.

.45 Colt +P isn't going to faze it.  Contact H&R/Marlin/Remington for peace of mind.

Warhawk, good point as I did see a 500 SW.