Hey folks, another head scratcher for me. I have used a comparator for my sizing for along time and never blew myself up. I was recently introduced to head spacing using the RCBS Precision Mic. I could t wait to use it on some already sized 22-250 bras. To my surprise I had .010 - .012 variances. I set up and sized more brass, measuring each one and low and behold, I cannot keep my size consistent. One will be +.005 and the very next one may be -.005. I am hoeing RCBS ram with Hornady dies. My Buddy was doing the same and decided to buy precision shell holders. His are now precise consistently. Can anyone explain to me why the shell holders would make such a dramatic difference?
Precision mic
- Thread starter Kentucky
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KyCarl
Well-Known Member
Does it come with a standard? How do you know if it's repeating?
Yes it does. It is set at zero for SAMI minimum case length.
ShtrRdy
Well-Known Member
Are you saying a shell holder is making the difference? If so, the only thing I can think of is if your friend has adjusted the die with a little "cam over" in the stroke.
The other thing that comes to mind not related to a shell holder is the brass may be work hardened and in need of annealing.
The other thing that comes to mind not related to a shell holder is the brass may be work hardened and in need of annealing.
I think you are talking about the Redding competition shell holders. These are useful in setting the shoulder bump. There are five in a pack, each is .002" higher than the other. Start with the small one, work up until the brass fits the chamber snuggly. The Precision Mic measures the amount of bump, if you also buy the dial indicator.
I have not done that, it's worth a try. Thank you
Yes that is the set I am talking about. I'm trying to wrap my head around why these shell holders are so precise on length and my Hornady ( and his ) are so erratic. Going from a .010 variance to a consistent.002. I guess I will just have to accept the facts and stop trying to figure it out. Thanks for your time and help
misterc01
Well-Known Member
I use my RCBS precision mic to measure and set headspace to .001-.002 back. The RPMic at zero is at min SAMMI spec. I am not using the Redding shell holders as what I am doing works for me. I have found that As part of the process, I have my headspace where I want it. Then I use a Hornady concentricity tool to get them at concentric. IMHO it sounds like a consistency issue. Once I get a case sized, all the following are the same.
Andrew Cowling
Well-Known Member
Inside neck lube too. If the case neck doesn't slip over the expander button freely it can pull the shoulder out with it.
misterc01
Well-Known Member
In my case, I am neck sizing, so I do not lube the neck. Match grade neck sizing die with insert.
