Being you were shooting 777 pellets before and are now going to shoot 777 loose powder you need to remember that the loose powder is much stronger then pellet powder.I personally judge it to be 15% but other claim they feel it as high as 20%. So if you were shooting 100 grains of pellets, then 85 grains of the loose should be about the same in strength. Of course you will have to try that in your rifle to be sure of the difference.

Also some rifles are not made to shoot 150 grains of loose powder, so keep that in mind. You might want to review your manual for load restrictions.