Use the non magnum 45 caliber XTP's for lower powered loads. They open up very nicely indeed! The 250 grain is rated from 750-1500 fps. I've clobbered 8 deer with that bullet driven by 70 grains of Swiss 3f. Chrono'd velocity 1600 fps. Nothing went past 50 yards. Those that moved at all were wobbling like a drunk.
One deer I shot with a Winchester 230 grain hp at 1450fps. Tore her chest UP! And exited too. She went a wobbly 30 feet or so. NEVER saw a bullet hold its core like those. Fired one into the dirt at 20 feet. There it was. A lead donut inside a FLAT jacket. Locked in there good and tight too! 200 grains remaining...
Something to keep in mind when shooting handgun bullets from muzzleloaders at higher velocities than they were ever meant to go. As they do not engage the rifling and their jackets are undeformed in any way, they CAN withstand higher velocities because there are no stress risers cut into the jacket by the rifling. You can read of some bullets being shot at 500 to1000 fps faster than rated and they perform well. The 250 and 300 grain non magnum 45' s and the 200 grain 40 caliber comes to mind. I'll put a vote in for the 180 grain 40 as well. I hit an 8 pointer with a 180 at 1750 fps. He was bent like a banana and the little pea got the left lung, the tip of the right, followed the abdominal cavity and wound up, (sans jacket) under the hide on the outside of the right ham. Still weighed 122 grains. I got one with a 200 grain 40 XTP at 1800 fps ( rated max 1250). 25 yard BOOMflop. IIRC, it got the ball of the shoulder, a rib, went like a blender through the lungs and wasn't found but did not exist. Not a bullet fail at all after hitting bone like that. She went 3 feet. Straight down. For economy, accuracy, consistency and lethality, it's VERY difficult to beat a well placed XTP. That Hornady is kind enough to publish expansion parameters is extremely helpful in choosing loads and very much appreciated!