the range and last but most important, that old bugaboo, shot placement
.
Yes it's the load too. For example a 60 grain load is the minimum here in Maryland, and at 50 yards with a .440 patched round ball, no worries, but at 100 yards with that round ball, I'd opt for 80 - 90 grains of 3Fg..., IF as Mykeal mentions, I can place the ball where it needs to go at that range.
The largest deer that I ever shot I got two Saturdays ago..., with a .54 at 60 yards, but he went 100 yards before he dropped, and it was a through and through lung shot. No blood either, which was odd. On the other hand I have had deer drop where shot or go less than 30 yards with the same load hit in the same spot at a longer range.
Some folks with the .440 RB use bullet alloy round ball instead of all lead, and a heavy charge, to get a through and through shot, not worrying about deformation as much as penetration. It is, after all, a .44 hole even without "mushrooming".
Now in your case a TC .45 should have a 1:48 twist, and a .45 caliber maxi-ball should up the mass of your lead-launching if you are worried or going out toward 100 yards.
Lyman , offers a mold as it seems they are no longer sold as pre-cast projectiles. They are not cheap molds, but it will solve your problem and with normal care will last generations. You are very close to doubling the lead you are shooting by going to a conical.
LD