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Wild Bill Bucks
August 2, 2006, 01:19 PM
I shoot a Thompson Encore. I can shoot 1 1/2" groups with a 44 magnum pistol bullet, in a Black Thompson Max sabot, with 100 grains of 777, all day. But when I go to 150 grains, I can't get on a 3ft square peice of paper at 100 yards. I have gone up in increments of 10 grains from 100, and it seems like the breaking point is at 130 grains. Groups still hold at 130 grains, but at 140, they are totally off of the paper.

Anyone else have this problem ? and What did you do to fix it? or are some guns that are rated for 150 grains, just not capable of handling the load?

arcticap
August 2, 2006, 09:42 PM
The volume of 777 needs to be reduced by approximately 15 - 20% over the factory recommended black powder loads depending on whether the 777 is ffg or fffg. It's a hotter and faster powder, so you may be exceeding the most accurate velocity, at least with 777 anyway.
Even the volume of loose Pyrodex fffg (pistol) needs to be reduced by about 10% when compared to Pyrodex ffg to compensate for the smaller granulation.

Another way of looking at it:
15% of 150 grains of BP = 150 - 22.5 grains for 777 ffg = 127.5 grains of 777 ffg
If using 777 fffg, and you reduce the powder volume by another 10%, then 127.5 grains of 777ffg - 12.7 = 114.8 or 115 grains volume of 777 fffg.

20% of 150 grains = 120 grains of 777 powder volume.

So these may be considered rough ballpark methods of determining equivalent powder volumes for 777, especially since I've never chronographed any powders to actually compare their velocities in any barrel.

Are you getting much fouling from the amount of 777 you're using?

Once you narrow down your load to within 10 - 20 grains or so, you can experiment using 5 grain increments of powder to better pinpoint the maximum accurate load out of a cold clean barrel to simulate the 1st shot when hunting.

Wild Bill Bucks
August 11, 2006, 02:07 PM
Found my answer. On your computer, type in "Guns and Shooting online"

Go to "General Firearms and shooting page" then click onto "Muzzleloader page"

Go to " Magnum Myth "

Pretty much told me why my gun won't handle 150 grain loads very well.

Sorry about the round about way to get to this article, but I haven't quite figured out how to get the info from my computer to the forum yet.