I've never had the pleasure to hunt elk with a muzzleloader. Soon I hope to change all of that. As for 100 grains and a good projectile, before all these magnum loads came out onto the black market field, most of the rifles were limited to 120 grains of powder according to the gun makers, some even less then that. A lot of elk were taken with charges around the 100 grain range. Also if extra powder causes uncomfortable recoil, then you will start to flinch which will effect accuracy. The most important thing is to put that shot in the right place and let the bullet do the rest of the work. I have no doubt it will take an elk....

Good luck!!