That is a post-WW2 Colt and is generally considered safe to at least 20k PSI loads in 45LC.
These include various maker's "modern combat loads" that are NOT marked "+P", such as a 200gr JHP doing 1,100fps, a 250gr JHP doing 900fps or a 250gr hardcast lead doing 1,000fps. There's a fair number of these loads out there as standard factory loads. Maximum ft/lbs of energy will be around 500 or so - at or slightly under modern high-end 40S&W loads but stronger (in raw energy terms) than anything in 9mm+P.
"Cowboy action loads" will be milder yet, and you might well consider doing most of your shooting with these. But you don't have to - that gun isn't "weak" by most standards.
See...loads that do NOT bulge or crack the cylinder in 45LC won't tend to do a lot of "cumulative damage". The cylinder either holds or it doesn't. If it holds, the rest of the energy applied to the frame and action parts are quite mild in 45LC with 20k PSI range loads.
Take the same gun in 357Magnum (which is usually a factory option) and you can raise the cylinder pressure to 43.5k PSI or more - because the cylinder walls are thicker. Top-end 357 loads can hit 800ft/lbs of bullet energy. But at this point you're putting more shock, crash and stress on the frame and action parts (that are the same as in your 45LC gun) and will actually wear the gun out faster on a "per shot" basis than high-end-but-still-safe 45LC loads for that gun.
Now, 45LC+P loads are another story entirely. DO NOT go there. These were made for large-frame Ruger single actions with much more cylinder wall beef than your Colt. They run up to 33k PSI chamber pressure and bullet energies sometimes up into 44Mag territory - over 1,000ft/lbs of energy.
Just ONE of the best of these can grenade your gun.
SAAMI spec for the 45LC is 14k PSI. Only pre-war Colt SAAs and some breakopen or otherwise abnormally weak 45LC guns (cartridge conversions, etc.) need to stay down in this power range. This is what the "cowboy action loads" are.
