DickK
05-17-2009, 05:12 PM
I stopped reloading October 23, 1983. I didn’t intend to but that day I blew a primer. The gases came back through the bolt and out the back, hitting me in the face. In shock, I tried to figure out what I had done wrong. I stopped shooting at that point.
This was my first test of IMR 4831 in my 257 Roberts Remington 722. Previously, all my loads were with IMR 4320 with 60, 75, 87, and 90 grain bullets. I never load cartridges to maximum pressure, no need to. My “regular” Loads were about halfway between “suggested” and “maximum”. I had done my research and thought 4831 would be a good choice for the 117 grain Sierra Spitzer Flat Base bullet. The suggested starting load was 40.0 grains and maximum was 45.0. Using new Winchester cases, I loaded up 5 rounds with 40.0 grains, 5 rounds with 40.5, 5 rounds with 41.0, and 5 rounds with 41.5.
When I began firing and inspecting the cases after firing, I began to be suspicious. All the primers indicated high pressure. The 40.0 grain batch had pretty well flattened primers. The 40.5 grain batch were the same but one had a raised crater. The 41.0 grain batch had one with a raised crater. The fifth round in this batch was the one that blew.
Here I am 26 years later trying to pickup where I left off. I’ve begun setting up shop for casting and reloading. I cleaned my lubricator and sizer. I’ve bought some moulds, a furnace, and some metal for boolits. I’m pretty satisfied with jacked bullet loads and decided I wanted to focus on cast boolits.
I’ve been refreshing my knowledge and memory about casting, reloading, and shooting. I was going through my inventory of ammunition and components when I found that box with the last unfired batch of 5 cartridges with 41.5 grains of 4831. I set up my press and pulled the bullets on 3 of the cartridges to check the powder weight. They had 39.6, 39.4, and 39.6 grains, just a bit less than the suggested starting load of 40.0 grains. I cannot explain why the weights are less by 2 grains than what the cases are marked. I weighed one of the bullets. It’s precisely 117 grains. I know there is a certain amount of solvent in powders that after 26 years may have evaporated but I don’t think it would amount to 2 grains. Also, the larger weight increments on the scale’s beam is 5 grains, I would have had to set at 40 grains. That means the smaller weight would have been at zero. I just can’t explain this difference.
Since the loads were pretty close to suggested starting loads, I cannot come up with a cause of the high pressure.
There is one other possibility, I mentioned above that the cases were new Winchester cases. The difference between them and the other cases I have is that they are marked “+P”. I tried to find out more about the Winchester +P cases without any success. I’m thinking the brass is significantly thicker than regular cases, such as the older Remington and Winchester ones I have. If it is thicker, then the case volume would be reduced and subsequently might cause high pressures. It is interesting to note Winchester sells only 257 Roberts +P ammunition.
Any thoughts?
This was my first test of IMR 4831 in my 257 Roberts Remington 722. Previously, all my loads were with IMR 4320 with 60, 75, 87, and 90 grain bullets. I never load cartridges to maximum pressure, no need to. My “regular” Loads were about halfway between “suggested” and “maximum”. I had done my research and thought 4831 would be a good choice for the 117 grain Sierra Spitzer Flat Base bullet. The suggested starting load was 40.0 grains and maximum was 45.0. Using new Winchester cases, I loaded up 5 rounds with 40.0 grains, 5 rounds with 40.5, 5 rounds with 41.0, and 5 rounds with 41.5.
When I began firing and inspecting the cases after firing, I began to be suspicious. All the primers indicated high pressure. The 40.0 grain batch had pretty well flattened primers. The 40.5 grain batch were the same but one had a raised crater. The 41.0 grain batch had one with a raised crater. The fifth round in this batch was the one that blew.
Here I am 26 years later trying to pickup where I left off. I’ve begun setting up shop for casting and reloading. I cleaned my lubricator and sizer. I’ve bought some moulds, a furnace, and some metal for boolits. I’m pretty satisfied with jacked bullet loads and decided I wanted to focus on cast boolits.
I’ve been refreshing my knowledge and memory about casting, reloading, and shooting. I was going through my inventory of ammunition and components when I found that box with the last unfired batch of 5 cartridges with 41.5 grains of 4831. I set up my press and pulled the bullets on 3 of the cartridges to check the powder weight. They had 39.6, 39.4, and 39.6 grains, just a bit less than the suggested starting load of 40.0 grains. I cannot explain why the weights are less by 2 grains than what the cases are marked. I weighed one of the bullets. It’s precisely 117 grains. I know there is a certain amount of solvent in powders that after 26 years may have evaporated but I don’t think it would amount to 2 grains. Also, the larger weight increments on the scale’s beam is 5 grains, I would have had to set at 40 grains. That means the smaller weight would have been at zero. I just can’t explain this difference.
Since the loads were pretty close to suggested starting loads, I cannot come up with a cause of the high pressure.
There is one other possibility, I mentioned above that the cases were new Winchester cases. The difference between them and the other cases I have is that they are marked “+P”. I tried to find out more about the Winchester +P cases without any success. I’m thinking the brass is significantly thicker than regular cases, such as the older Remington and Winchester ones I have. If it is thicker, then the case volume would be reduced and subsequently might cause high pressures. It is interesting to note Winchester sells only 257 Roberts +P ammunition.
Any thoughts?