wow! you ever think of writing your own book? Unfortunitly i only have brass that has been " messed with" . But i do understand what you are telling me. basiclly, don't work the brass so that it moves excessivly in the chamber, but work it enough that it feeds in and out with out resistance. so maybe I should re examine my resizing die ?
Primer Problems
- Thread starter browndusti
- Start date
- Location
- Somewhere on the Hudson Bay Coast
This is all fine and good but does not really address why the primer backed out of the case. Even if there is excessive head space caused by full length resizing, the case will stretch until the case head contacts the bolt face, or until the case fails. I would be interested in seeing a fired case to see if there are signs of excessive stretching which is evidenced by the appearance of a bright ring around the web of the case. If there is no sign of excessive stretching, chances are that the head space is close enough.
Lets go through the stages of what happens when the cartridge fires. First the primer goes off, and the force of the primer forces the powder column against the base of the bullet which moves forward until it contacts the rifling. The powder column then ignites, and gas pressure increases which expands the brass case until it fits tightly against the walls of the chamber creating a gas seal, and the primer backs out of the primer pocket from gas pressure through the flash hole. The pressure continues to build, and the case is driven backwards until it stops against the bolt face. The case stretches forwards until the shoulder of the case contacts the shoulder of the chamber. At this point in the process, the bullet begins to move down the bore.
Therefore, if sufficient pressure is created by the expanding gases of the powder charge, the primer is set back into the primer pocket when the case head contacts the bolt face. If the primer is not driven back into the primer pocket, the only answer can be a lack of sufficient pressure. this can create a dangerous situation if there is not enough pressure for the cartridge case to expand to make a gas seal in the chamber. The gas can collapse the cartridge case and flow back into the action.
Lets go through the stages of what happens when the cartridge fires. First the primer goes off, and the force of the primer forces the powder column against the base of the bullet which moves forward until it contacts the rifling. The powder column then ignites, and gas pressure increases which expands the brass case until it fits tightly against the walls of the chamber creating a gas seal, and the primer backs out of the primer pocket from gas pressure through the flash hole. The pressure continues to build, and the case is driven backwards until it stops against the bolt face. The case stretches forwards until the shoulder of the case contacts the shoulder of the chamber. At this point in the process, the bullet begins to move down the bore.
Therefore, if sufficient pressure is created by the expanding gases of the powder charge, the primer is set back into the primer pocket when the case head contacts the bolt face. If the primer is not driven back into the primer pocket, the only answer can be a lack of sufficient pressure. this can create a dangerous situation if there is not enough pressure for the cartridge case to expand to make a gas seal in the chamber. The gas can collapse the cartridge case and flow back into the action.
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Boomer; normally your explanation is what I would expect to happen too. But he was using a minimum load from the book. Enough pressure so the brass clings to the chamber but not enough to stretch it fully. It actually happens quite a bit with reduced pressure loads and cast bullet shooters run into from time to time. The case probably is stretching a bit but not all the way . From there it sounds like he has maintained a resized case shoulder length established from a case that has not fully fire formed to length on the first firing. Consequently his next re-sizing compounded that and shortened it a bit more.
Unless he gets it back to the right length soon he will see a web top separation sooner than later. If I had his brass I would load it with a cast bullet that was a force fit in the lands and that would certainly hold the case to the bolt face and move the shoulder back forward. It could be done with jacketed bullets as well with a minimum load provided the bullet was simply seated to be firm against the lands
Unless he gets it back to the right length soon he will see a web top separation sooner than later. If I had his brass I would load it with a cast bullet that was a force fit in the lands and that would certainly hold the case to the bolt face and move the shoulder back forward. It could be done with jacketed bullets as well with a minimum load provided the bullet was simply seated to be firm against the lands
Boomer; actually we are in agreement on the need to increase the load and get the pressures up and the firing occurences in the chamber. I think he does have to reset his sizing die and whether he is ready to get his current batch of brass fire formed correctly I can't answer. He might be better off to get a new batch and start over and reserve the old stuff until he is confident in his procedures and do it then.
- Location
- Somewhere on the Hudson Bay Coast
Yes, and I agree, that once his brass has stretched to match the length of his chamber there is no need to full length resize. Perhaps the brass used for light loads should be kept for that purpose and only neck sized. I generally prefer to bump the shoulder back slightly when I load for accuracy with normal powered loads.
OK, Is there any other signs of low pressure problems that i can look for on my brass? also, my brass does not seem to grow very much (001-0015) if that helps you with my problem or not. so are we in agreeance i should make up a lot working up my loads and see if there is any changes?
browndusti: That is what I would do. I know Nosler refers to the .005 -.006 set back but that would be with a fully fire formed case. At that I believe it to be excessive and about .002 is probably a better way to go as long as the brass chambers freely. Not that Nosler's comment is so out of line that it is dangerous as it isn't. Only that case life and accuracy will be enhanced by doing the minimum amount of brass working. Unless you have one of the Stony Point tools that actually measure to the datum line I think you are best to do it by feel. The short case stretch you mention is about what I thought you might be getting and the reason you have primer protrusion. Have you tried measuring the protrusion by the way? It might give you an idea of how much to reduce your re-sizing.
When oversizing, case stretch will eventually accumulate near the rear of the case leaving a thin spot inside the case and that is where separation can occur. I think Nosler has a cross sectioned case picture that will show you this although it may not have occurred from the identical circumstance.
When oversizing, case stretch will eventually accumulate near the rear of the case leaving a thin spot inside the case and that is where separation can occur. I think Nosler has a cross sectioned case picture that will show you this although it may not have occurred from the identical circumstance.
ok i shot my way up to the max listed load with no primer problems. BUT that was with the CCI primers, so now i am going to shoot my way up with win primers and see if there is any differance. the only noticable change that i seen was my casings seemed to get a lilttle bit blacker. i did not find any golden rings on my casings.
