When they shoot those 150 grain loads most of that is done with 3 pellets.

As for powder choice, Triple Se7en 2f is a great powder without question. The thing you might experience using it is a hard crud ring build up down in the breech. That should be removed after every shot so that means you are swabbing the barrel before reloading each time. That is not all that big a deal actually and after a while it becomes second nature to you.

Pyrodex RS is another great powder. Very consistant. Very cost effective when you compare it to other powders and even better when you get it on sale. It will fowl a barrel, but the fowling is much softer. It is also recommended that you swab that fowling out between shots.

Another powder that sometimes shoots real well out of rifles is Amercian Pioneer Powder a.k.a. APP. It is a sugar based powder that you do not have to swab between shots. It loads easy, cleans easy, but some people do not get the kind of accuracy they want. Jim Shockey has a powder out called Shockey Gold which is APP powder. He shoots a Pro Hunter I believe. APP is kind of expensive where I live, and in some of my rifles works fine, in others not worth a hoot. APP is also not very corrosive. I ran some tests on different powders where I tried to rust a lawn mower blade. It was interesting to see which powders really start to effect the metal fastest.

So when I purchase powder I look for consistancy shot to shot, ease of swabbing, and cost. My choice is Pyrodex RS and Triple Se7en 2f. I shoot a lot of Pyrodex RS and Pyrodex P. I think a lot of people get the Triple Se7en because it is a little more powerful the Pyrodex RS and easier to clean up. If you count a couple minutes of your time with a rifle as that important. Also Pyrodex RS is very corrosive. You shoot it, you clean that rifle. Triple Se7en is not as nasty and will give you some time between shooting and cleaning if say you are in a situation where you can not clean the rifle right away.