I do with 350 grain FPB in my CVA Optima. For brush load for whitetails. small hole in, big hole going out and leaking blood really fast.

After reading a number of articles on velocity and pressure I came to the conclusion that any load over 120 grains is counter productive. One article measured velocity and pressure of loads Starting low and increasing by as I recall 10 grains or possibly 20 grains. From the starting point each increase in velocity was by about 200 fps and as expected a gradual and constant increase in pressure. That is till the 120 grain load. From 120 to 150 grains the increase in velocity was averaged at 85 fps but the pressure and resulting recoil was increased manyfold. Rifles can be produced to be reliable with those shoulder bruising loads but unless the barrel is long enough to completely burn that much powder all one does with more than 120 grains is blow more smoke.

Ive also heard that when you get up to around 150 grains the accuracy starts to suffer.  Faster isn't necessarily better when it comes to muzzle loaders.

I use three pellets of 777 with a 250gr bullet/sabot in my Omega with a Nikon Omega BDC at 100yds 1" groups. But big rig is right with some guns more isn't better. You have to work up a load that best suits YOUR gun. Your Omega may not shoot like mine with the same load.

GutPile: Your right on with your comment. I also have a newer Omega Z5 with a Nikon 3x9 on it. I have tried loads with Pyrodex "P", "RS" Triple Seven FFg, and FFFg, Jim Shocky Gold "Crap", and 777 50 gr Pellets behind many different bullets. I found the 150 grain loads were less accurate off the bench with ALL bullets tested than was 130 gr of 777 FFg powder, behind the 295 gr powerbelt with a 777 primer. (Remington Standard 209 primers also worked well & Cheaper) The only problem was the powerbelts had a 3" group at 200 yds, but blew apart on deer closer than 150 yds. Yes they killed the deer, with a considerable amount of damage, but ruined a lot of meat! I know, shot placement has everything to do with it! But sometimes the perfect shot, doesn't go perfect! I ended up using The Hornady MAG Express sabots with a 250 gr jacketed bullet. WOW these are almost as accurate as the powerbelt bullet, (still working that load for more accuracy) but perform much better when they encounter venison!
   Every rifle is different and working up loads is part of the experience with Black Powder hunting! Good Luck!

IMHO Powerbelts are junk. I shot a big doe at 130yds shot placement was right on. Dropped her in her tracks. When I got up to her one of the first things I noticed was the snow behind her was pritine. No hair no blood. On futher inspection I found no exit wound. However when I opened her chest cavity the lungs and heart were full off holes from 1/4" to 2" litterally destroyed. The only sign of the Powerbelt was the plastic skirt lodged in the entrance wound. None of the people I know that used them at ranges from 75-150yds had any exit wound all deer were recovered. I switched over to the TC Shockwave 250gr and on the range could shoot groups of three almost touching at 100yds. When an oppurtunity arose I hit a buck in a cornfield at 200yds. He ran 25yds and died. The bullet passed through. When I got into his chest the wound channel was huge. Pretty much turned his lungs to jello. Because I'm A Vet Tech doing a post mortem on a kill is second nature for me.

I drop three pellets behind a 405 grain powerbelt. I deer hunt in South Jersey. My CVA Optium is sighted in at 50 yards, which is about the farthest I can see in the woods. I own 7 muzzel loaders. All 50 calib. Started shooting black powder about 22 years ago. Use to melt my own lead and pour Pydrex down the barrel. Started with side locks and then went to a Knight MK85 when they came out. Bought the Optium to shoot 150 grains as the knight was maxed out at 100 grains.
Joe Termite

Never found the extra ump on the shoulder an advantage with a ML on groups .And a deer hit with half that powder is DOA . Use 75 FF BP with the flint lock and 90 FF Trip 7 with the Knight (Knight is super tight at 100 with that) older one 120 max .

I have played on the range with 150 grain loads. Shooting 3 pellets in my T/C Black Diamond XR I got very good accuracy with the 250 grain shockwaves, but never used that load hunting. No need for it really. When shooting loose powder I like to say under 120 grains but again, have just for the experience of the kick, fired off 150 grains of loose powder. Other then being kicked badly, and laughing about it.. there was no need for that either.

A common load in the longer barrel rifles is 110 grains of loose powder. But in my short barrel rifles like my Knights.. 85 grains is an excellent load. 100 grains is a nice powerful load with sabots. And I have shot as little as 65 grains of powder when shooting large conicals. All of this is hunting loads.

If you want to shoot 150 grains of powder, and it is accurate, just make sure the bullet you use is made for those kind of velocities. Bullets such as Thor, Barnes, Nosler, Lehigh, even Parker.. they can handle those kind of charges. Others tend to fragment too quickly according to my testing. But let me state.. my testing is not into live flesh. So how that same bullet would react in a deer for instance.. only in the field experience can tell.