Although Bullseye is a really fast powder for the 44 Magnum, unless you are already at maximum safe pressures, the use of magnum primers is not going to be a problem.

I will say that a huge potential problem with Bullseye, AA#2, W-231/HP-38 and any similar fast burning powder is that safe charges take up very little room in those huge cases. This makes the accidental double charging of a case a real possibility, so extra care must be used to make certain that no case receives a double charge.

Personally, I stick with medium burning rate powders in the magnum cases when I want less than magnum velocities. In these cases, Unique is my friend.