Gentlemen: I sized and trimmed a bunch of brass, using rcbs dies, and a Lee shell holder. my guess is things wound up a bit short as I am getting head separation, so I think I need to make them a little longer. there is no other sign of pressure. so... my seemingly best idea is that I can do this by setting the die with a shim on top of the tool holder. any other suggestions would be appreciated.
Making 308 norma magnum brass out of 300 win brass.
- Thread starter 22to45
- Start date
Only size the cases back to where they are hard to close the bolt on in your rifle. Then trim to length. - dan
- Location
- Western Manitoba
As mentioned above - the most common cause of head separation is air gap between bolt face and wherever that cartridge is meant to headspace - that might be the shoulder area; or that might be the forward face of the belt - usually your best bet is to oversize the neck, then bring down the correct sized die a bit at a time and keep trying in your rifle. You are trying to create a "false shoulder" that has minimal end-play - then fire form to blow out the shoulder, and then neck size, or partially full length size, carefully, going forward. Case head separation, especially on home made cartridges, usually has not much to do with the shell holder used.
As mentioned above, you want to end up with your re-formed case hard on your bolt face and snug to your headspace point. In theory, most rimmed cases and belted cases do not normally headspace on their shoulders - although some can be made to do so. In most cases, the rim or the belt was added to create or improve the headspace of that cartridge. I believe that your 308 Norma Magnum is a case that might benefit from "head spacing" on its shoulder, instead of it's belt. Since the belt will no longer be involved in controlling headspace, and apparently does nothing about case or case head "strength", it becomes entirely superfluous.
FYI - a shell holder does not need a shim on top - is common enough to see light between the top surface of a shell holder and the bottom surface of the sizing die.
A Norma brand 308 Norma Mag on left and Norma brand 300 Win Mag on right
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