Tenmilephenom

That is probably a good idea...

If you had a chrono you could clock you load then start backing down in 10 grain increments and if the velocity dropped you would know you are getting the most out of your powder but if stays the same you are getting a good burn.

Another way as some of the old timers tell me you could shoot it across snow and if it is spitting out unburnt powder you would see it in the snow in front of you...

But the real result of this is if it is working why fool with it... powder is not that expensive - results are..

Yeah - you are pushing it. 90 grains 777 FFFis more than enough out-to 150 yards. The 300 XTP was built for magnum-like pistol speeds. Like the Powerbelts, they prefer sub-100 grains.

I used a 300gr XTP and 100gr Pyrodex R/S to drop a deer in it's tracks this year. My rifle shoots to approximatelythe same POI @ 100 yards with 100gr Pyrodex or 80gr T-7. Just happened to be using Pyrodex that day since it was pouring rain and I didn't know how moisture might affect the T-7. [&:]
I guessed the shot to be about 80 yards, but it was actually closer to 100. Quartering-towards me and I put the bullet in front of the shoulder. No exit & a dead deer dropped on the spot!
Unfortunately it was pouring rain, I had my 7 year old with me, it was getting dark, and the creeks were rising fast (and we had to cross one), so I field dressed it as quickly as possible and got it out of there! No time for an autopsy, but I could tellthe lungs were destroyed!