I've never loaded mine with more than 150 grains by volume of propellant but with more I bet they hit hard both ways!
Speaking of hitting hard, a friend and fellow gun club member was shooting his old Winchester Epex(?) muzzleloader this morning and became distracted, causing him to double-charge it with 220 grains of Blackhorn 209. The scope's ocular lens cut into his nose, his shoulder hurts and the action is frozen but the gun didn't grenade. I loaned him my T/C Encore ProHunter for next week on the condition that he load it with no more than 100 grains of Alliant's Black MZ.
If you haven't tried that propellant, you should. It smokes less than anything but Blackhorn 209 (and it doesn't smoke a lot more than 209), doesn't leave a Pyrodex/Triple 7 "crud ring" in the chamber, cleans up with regular water-based black powder solvents, is non-corrosive, is as accurate in my two guns as 209 and costs a whole lot less. Around here, a pound of Black MZ costs about $25.00 while 209 is $38.00 for just 10 ounces! If you're opposed to using loose powder, Alliant also sells Blue MZ, basically the same thing in pellet form.
Ed