Howdy - hopefully this is an educational topic.
I am one of those reloaders who shoulder bumps AR-15s .003" and my bolt actions .002" instead of following the manual (touching shell holder then quarter turn). This has extended the life of my brass and reduced the need to trim (though it happens infrequently that I need to trim).
I spend a significant amount of time setting up the sizing die to get the shoulder bumped. I use all LE Wilson tools for measurements (case gauge and case gauge depth micrometer). I don't trim my 6.8 to 1.676", I trim to flush with the LE Wilson case gauge (which will account somewhat for my specific chamber). The reason I spend a lot of time setting up the dies is because, after I get the proper shoulder bump set up ono the first case, I got to the next 4 cases and it's anywhere between .001" and .005" off from the first case. I initially decided to just let it go and keep them consistently set on the same setting of the die, but I'm running into a problem. Some cases don't bump as much as the 1st one or the 5th and and, because these tolerances are so tight, I'm getting cases that are getting stuck in the chamber because apparently they didn't bump at all (a little cratering will get them out). I thought at first I would just start bumping the shoulder back further, but that's just a bandaid to a problem. So I researched it and found this article. It's a long article and the meat of it is lower in the thread. But the bottom line is two things that cause this 1) press flex 2) when we do minimal shoulder bumps, there is sometimes a gap between the bottom of the die and the shell holder and this gap is inconsistent. Ideally, each piece of brass would require a cam over, which is why the instructions lead you to that.
Two solutions are recommended: 1) buy an Iron Press 2) buy Redding's Competition Shell Holders which are adjustable and allow you to adjust the gap out of the shell holder<>die. Better explained by Redding:
I am one of those reloaders who shoulder bumps AR-15s .003" and my bolt actions .002" instead of following the manual (touching shell holder then quarter turn). This has extended the life of my brass and reduced the need to trim (though it happens infrequently that I need to trim).
I spend a significant amount of time setting up the sizing die to get the shoulder bumped. I use all LE Wilson tools for measurements (case gauge and case gauge depth micrometer). I don't trim my 6.8 to 1.676", I trim to flush with the LE Wilson case gauge (which will account somewhat for my specific chamber). The reason I spend a lot of time setting up the dies is because, after I get the proper shoulder bump set up ono the first case, I got to the next 4 cases and it's anywhere between .001" and .005" off from the first case. I initially decided to just let it go and keep them consistently set on the same setting of the die, but I'm running into a problem. Some cases don't bump as much as the 1st one or the 5th and and, because these tolerances are so tight, I'm getting cases that are getting stuck in the chamber because apparently they didn't bump at all (a little cratering will get them out). I thought at first I would just start bumping the shoulder back further, but that's just a bandaid to a problem. So I researched it and found this article. It's a long article and the meat of it is lower in the thread. But the bottom line is two things that cause this 1) press flex 2) when we do minimal shoulder bumps, there is sometimes a gap between the bottom of the die and the shell holder and this gap is inconsistent. Ideally, each piece of brass would require a cam over, which is why the instructions lead you to that.
Two solutions are recommended: 1) buy an Iron Press 2) buy Redding's Competition Shell Holders which are adjustable and allow you to adjust the gap out of the shell holder<>die. Better explained by Redding:
Thank you for using Redding Reloading Equipment. If your Full Length Sizing Die is adjusted to just make contact with the shell holder, and you run a case up into the die. You will see a gap between the bottom of the die and the top of the shellholder. What happens is when the case pushes up on inside of the die and it removes the play between the threads of the die and the threads of the press. There is also some flex in the press itself, even Redding Ultramag Press will flex. Each piece of brass will have a different amount of resistance to resizing. So this gap will vary, which gives you a variation in shoulder setback.
Redding's Competition Shellholders allow you to adjust your die for a cam-over (screw the die down another 1/8 to 1/4 of a turn) and eliminate this gap. You then adjust the shoulder set back by using the Competition Shellholders. You start with the +.010 and work back toward the +.002 shellholder until you achieve the shoulder set back you want or your bolt handle will close freely. You may still see some variation due to difference in spring back of each piece of brass.
I hope this helps.
Regards
Chris Fox
Customer Service
Redding Reloading Equipment
What say you? Looking for input/experience from folks on this forum.
Redding's Competition Shellholders allow you to adjust your die for a cam-over (screw the die down another 1/8 to 1/4 of a turn) and eliminate this gap. You then adjust the shoulder set back by using the Competition Shellholders. You start with the +.010 and work back toward the +.002 shellholder until you achieve the shoulder set back you want or your bolt handle will close freely. You may still see some variation due to difference in spring back of each piece of brass.
I hope this helps.
Regards
Chris Fox
Customer Service
Redding Reloading Equipment
What say you? Looking for input/experience from folks on this forum.