my first non hunting load test (pre break down)

[corey012778]

I have been post on a test i am going to do in the near future. conical out of a sabot.

Break down of what I have done before shooting one:

Pushed out a load that I had in for 2 week (I was being lazy)
pushed a great planes 45cal 285 gr in a mmp hph 24 black sabot thru the barrel. (went down pretty well)
wiped the lube off of four of them (only had 4 tubes lift to load). edit moved it up to 5. I was going to work on some shockwave but changed my mind.
?

The only problem I am having. can't deside how much of a charge to use. I am thinking of 70grs, 75grs, 80grs, or 85grs (pet charge right now) of pyrodex p.
edit: I went with 70grs of pyrodex p.

so I am going to pole yall, which one would you use with this test?

note: it is going to be at 50 yrds with a knight usak