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My favorite .45 Colt load is a 230 grain lead bullet (you could use a 250) with 7.5 grains of Promo powder (cheap variant of Red Dot.) This is hotter than a standard load, but not by a lot, and it is *really* cheap to shoot -- especially cuz I cast the bullets using free scrap lead.
A couple of loads for that rhino you mentioned: 250 or 255 grain cast bullet with 12.2 grains of Herco or 16.5 grains of Blue Dot. You can go even higher with 2400, AA#9, Enforcer, or 296 powders, but 296 is tricky to work with. All of these loads are fun to shoot maybe a dozen rounds, then the fun wears off really quickly. The Red Dot load I gave or some of the midrange Unique or Universal loads, you can shoot them all day.
Also try some blackpowder. .45 Colt was made for blackpowder. But wash the gun with hot water when you're done and then clean it really well.