Jim
05-29-2013, 04:13 PM
A while back, a friend gave me a Lyman 462560 single cavity mold to play with. After running off several dozen boolits, I discovered it was dropping at .453! I got the mold fixed and it's now dropping at .460 to .461.
I ran off a bunch yesterday, sized and checked 'em and gave 'em a good coating of my Graphlox lube. They were completely dry this morning, so I decided to run a pressure test using IMR 7383.
After determining that 100% case capacity is 42 grains, I started at 43 grains and worked up 1 grain at a time. I was really surprised to find that I was able to go to 50 grains without any pressure signs.
I've done a lot of research and testing with 7383, so I'm very familiar with this powder. I've used it at 100+% case capacity charges in my .45-70 before, but the heaviest boolit I used to date is a plain based 500 gr. round nose bore rider. I didn't expect to be able to go to a 115% charge with a boolit that is 10% heavier.
If you're not familiar with 7383, DO NOT confuse the ability to run this powder at 100+% charges in tapered cases with the ability to do this in bottlenecks. This is a strange and quirky powder and it can be very spikey in bottleneck calibers.
Nothing about this test was toward accuracy. I was simply looking for the top of the pressure window. Judging by the results, I still don't think I'm there. One of the signs that 7383 exhibits when it reaches peak pressure is that all the powder burns. Prior to peak pressure, you'll see unburnt granules in the barrel. Even at 50 grains, I was still seeing a little unburnt powder. I found no difference in primer prints between 43 grains and 50 grains. I did notice, however, a detectable increase in recoil.
LOADED ROUND & BOOLIT
71922
PRIMERS, 43 grs. & 50 grs.
71923
I ran off a bunch yesterday, sized and checked 'em and gave 'em a good coating of my Graphlox lube. They were completely dry this morning, so I decided to run a pressure test using IMR 7383.
After determining that 100% case capacity is 42 grains, I started at 43 grains and worked up 1 grain at a time. I was really surprised to find that I was able to go to 50 grains without any pressure signs.
I've done a lot of research and testing with 7383, so I'm very familiar with this powder. I've used it at 100+% case capacity charges in my .45-70 before, but the heaviest boolit I used to date is a plain based 500 gr. round nose bore rider. I didn't expect to be able to go to a 115% charge with a boolit that is 10% heavier.
If you're not familiar with 7383, DO NOT confuse the ability to run this powder at 100+% charges in tapered cases with the ability to do this in bottlenecks. This is a strange and quirky powder and it can be very spikey in bottleneck calibers.
Nothing about this test was toward accuracy. I was simply looking for the top of the pressure window. Judging by the results, I still don't think I'm there. One of the signs that 7383 exhibits when it reaches peak pressure is that all the powder burns. Prior to peak pressure, you'll see unburnt granules in the barrel. Even at 50 grains, I was still seeing a little unburnt powder. I found no difference in primer prints between 43 grains and 50 grains. I did notice, however, a detectable increase in recoil.
LOADED ROUND & BOOLIT
71922
PRIMERS, 43 grs. & 50 grs.
71923