If your barrel is only 26 inches, you might be better off using Pyrodex P powder, than the RS powder size. The P powder will burn hotter, and give you more velocity from that short barrel. Because Pyrodex, and the other substitute powders burn at a MUCH hotter Temperature than does BP, use a OP wad, or filler, to protect the conical bullet from gas cutting.
The Bullet does need to be going Faster to remain stable at the longer range, particularly out of a 1:48 ROT. That is generally considered a compromise ROT, because you can shoot both RB, and Short Conicals accurate from such a barrel.
Any time you lengthen a bullet, and add more weight, you generally have to increase the ROT to stabilize the longer bullet.
The Recoil can be brutal shooting heavy bullets. I join in recommending you consider shooting a RB for deer in that gun, and do some comparison penetration testing, before you decide that a RB is " inadequate" for deer.
I have been shooting deer with my .50 cal. rifle for years, and never needed a second shot. My first deer was taken at 40 yds, and the ball passed completely through the chest, breaking ribs going in and exiting, while hitting both lungs, and some of the major arteries above the heart in the middle. I don't know what MORE penetration you could possibly want from any projectile used to hunt deer.
By far, the vast majority of shots on deer are taken at well under 100 yds. I have seen deer crossing a open field more than 200 yds from my stand, but that is the rare exception. Usually they are hugging the brush lines along forests, or staying in the forest on the other side of the edge brush. :surrender: :thumbsup:
