I am currently only shooting 100 grains of triple 7 pellets (2) along with a 250 grain bullet out of my muzzleloader. If I change the amount of powder up to 150 grains, how much would my shot be off, say at 100 yards? I know that I should go to the range, and I will, but I was just curious to what I should expect at the range.

I'm gonna guess the velocity alone will cause a decrease of about 1" in total drop @ 100yds. Your sight height and sight-in distance and all that good stuff will be your other variables. So you'll probably have more than a 1" raise in impact. Hit the range, give us a report.

The only way to know will be to shoot it. Why do you think that you need 150 grain charges? There really is no need for such a large load for deer.

Mike

The problem is the group might open up to 6-8 inches, no way to know without shooting...The other problem, it's going to kick the snot out of you...

I shoot 80grs of FFF Goex in my flintlock and have over 20 years...I use 90grs of FFF Goex in my Knight with a 250 Shockwave...I'm 3 inches high at 100 yards and 3 inches low at 150, that's far enough...

Remember the 45/70??? It was a .45 caliber lead bullet with 70grs of black powder behind it...Many, many buffalo were killed with that caliber...

curt - This would be better asked in the blackpowder forum but I can probably help you out. When I had my inline, I called the manufacturer and he told me that although the rifle can easily handle a 150 grain charge, 100 gr is plenty. With 150 gr you will just be wasting powder.
And if the 100 gr charge is working for you that is plenty for deer or black bear with the 250 gr bullet. No, IMO, although the pellets are OK, you may be better served with the loose powder and a volumetric measurer. With these, you can adjust your powder in 10 or 5 grain increments until you find the most accurate charge for your rifle/bullet combo. Start with 80 gr of 777 and work up. I would say to no more than 110 or 120 grs.

.......bronko is right...this really belongs in the "blackpowder" forum. But I, too, will offer a little advice here... I shoot a CVA Wolf inline when season allows here in PA. I've tried 150 gr. of Pyrodex in it, just because it's capable of handling it. Aside from loosening several molars and causing my eyes to rotate in opposite directions, I quickly went back to a 100 gr. load that shot goooood in my gun. The 150 load opened up dramatically, and just beat the livin' bejeesus out of me. Nooooo need for it here on a whitetail or black bear...period.