Beleg2,
I recently purchased a .50 caliber 700 Remington inline muzzleloader and measured the twist rate at one turn in 28 inches. I will use this gun out at our farm for longer range shooting on our local deer population. I have not had time to work up loads for it yet but I have had good results in the past with sabots loaded with heavy bullets powered by two 50 grain Pyrodex pellets and a 209 shotgun primer. My gun has the 209 primer nipple added to it. I don't think 150 grain loads are necessary for deer or hog sized game. I hope this helps. Bob H.