D.B. Cooper
Member
- Joined
- Oct 2, 2016
- Messages
- 4,400
Choose. But choose wisely.
I'm putting together a load for caribou for my 243 Winchester using an 85 grain Barnes TSX HPBT (not the tipped) projectile and Hodgdon Superperformance powder. I need to choose between the most accurate load or the fastest load.
My best accuracy was about 1/2 MOA from 42.7 grains. That's near the starting charge of 41.2 grains. I didn't have a chronograph then, so I don't know the velocity, but I estimate it to be about 2900 fps. (I seem to gain or lose about 75 fps for every 0.5 grain change in powder charge.) Next-best accuracy was just over 1 MOA from 43.7 grains at 3052 fps.
Barns recommends a terminal velocity of at least 2000 fps for proper expansion. According to my ballistics calculator, the 2900 fps load drops to 2000 at 350 yards and is still supersonic at 850 yrds.; the 3052 fps load (is 150 fps even enough to worry about?) drops to 2000 fps at 400 yards and is still supersonic at 900 yards.
SO...the slower, more accurate charge works out to be a max effective range of 350, and at 350 and half MOA, that's a roughly 1-3/4 group. (I'm not that good of a shooter to hole 1/2 MOA from a field position.) The kill zone on a caribou is roughly 12-14 inches.
The faster, less accurate charge works out to be a max effective range of 400 yards, and at 400 and just over 1 MOA, that's roughly a 4" group.
Just from typing this up and re-reading it, I'm wondering if there is enough difference between these two to make a difference. Both are probably sufficient for my purpose. (Neither are what I would call stellar.) I also have to ask myself if I would even shoot a caribou at 350 or 400 yards.
Anyway. Tanks for reading my lengthy post, and I look forward to hearing your thoughts.
I'm putting together a load for caribou for my 243 Winchester using an 85 grain Barnes TSX HPBT (not the tipped) projectile and Hodgdon Superperformance powder. I need to choose between the most accurate load or the fastest load.
My best accuracy was about 1/2 MOA from 42.7 grains. That's near the starting charge of 41.2 grains. I didn't have a chronograph then, so I don't know the velocity, but I estimate it to be about 2900 fps. (I seem to gain or lose about 75 fps for every 0.5 grain change in powder charge.) Next-best accuracy was just over 1 MOA from 43.7 grains at 3052 fps.
Barns recommends a terminal velocity of at least 2000 fps for proper expansion. According to my ballistics calculator, the 2900 fps load drops to 2000 at 350 yards and is still supersonic at 850 yrds.; the 3052 fps load (is 150 fps even enough to worry about?) drops to 2000 fps at 400 yards and is still supersonic at 900 yards.
SO...the slower, more accurate charge works out to be a max effective range of 350, and at 350 and half MOA, that's a roughly 1-3/4 group. (I'm not that good of a shooter to hole 1/2 MOA from a field position.) The kill zone on a caribou is roughly 12-14 inches.
The faster, less accurate charge works out to be a max effective range of 400 yards, and at 400 and just over 1 MOA, that's roughly a 4" group.
Just from typing this up and re-reading it, I'm wondering if there is enough difference between these two to make a difference. Both are probably sufficient for my purpose. (Neither are what I would call stellar.) I also have to ask myself if I would even shoot a caribou at 350 or 400 yards.
Anyway. Tanks for reading my lengthy post, and I look forward to hearing your thoughts.