".45LC+P" happened when Ruger first built 45LC SAs on a 44Mag frame around 1973 - and gave the frame/cylinder the same heat-treat AND did the same hand/ratchet/innards. S&W doesn't do this; their 45LC N-Frames are weaker than their 44Mags. (Colt Anacondas have the same heat-treat between both calibers, ditto Dan Wesson.)
45LC is classically able to deal with about 15,000psi (in older guns) and modern guns can run up to 20,000 "without trying hard" (more or less anything made in the latter half of the 20th century with a solid frame). That's why you can run Cor-Bon's 200grain JHP @ 1,100fps even in an Italian SAA clone...although not a steady diet.
The Rugers can be pushed to 35,000psi and loads that will kick the rumps of most 44Mags. Bufallo Bore sells a 325grain @ 1,300+ and if you stick this in anything of lesser strength it'll grenade. Ruger DAs (RedHawks/SuperRedHawks) are as strong as the SAs.
Everybody who deals with the 45LC knows this, and the various packagings are quite clear.