Seating 8mm gas checks with a seating die and a lee sizing ram

Here’s a cool trick that I figured out over the last few days. I’m sure someone else thought this up before me, and has been doing the same thing for years. But this method is new to me.

1. Use a Lee deburring tool to clean up the bottom of my gas check shank.
2. Partially seat a gas check.
3. Thread the seating stem into the seating die backwards, and install the die into the press upside down.
4. Install the Lee sizing ram onto the press.
5. Seat the check slowly rotating a quarter turn three or four times until the check is seated.
6. Dip lube in 50/40/10 beeswax/Lar’s Xlox/paraffin.
7. Size to .323” on Lee sizer.
8. Size again to .318 on a honed out Lee sizer.
9. Tumble lube in 45/45/10 Lar’s Xlox/Johnson’s PW/paint thinner.


A little backstory. I have a mold, an NOE 325 365 that drops a boolit that measures .302” at the gas check shank. My checks I.D. measures .300”. I can get the checks started by hand, and sometimes seated, but almost always crooked.

A little more backstory, I had an Lee 324-175 that was even worse. It’s shank was even larger. I gave up on that mold, and drilled it out to make a plain base mold. I posted about it and multiple people mentioned the NOE check seating tool. I watched a video about this tool, and this is what got me thinking about a way to seat these checks with tools that I already had on hand. Both of these bullets that I’m working on are for my 7.7x58mm Japanese T99, that has a .3165”. I’m sizing them down to .318” in a honed out .314 Lee sizing die.

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Took a minute to understand until i saw your pics what was going on. I have run into the same problem, but with the .224 Lee six cavity mould/boolit design. Thanks for posting; the .22 cal checks are tiny in my fat paws and I am gonna try this as it looks as if it might be a solution. I think NOE makes a check expander but this may be the way to get by without one.

Quote:

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Originally Posted by wmitty

Took a minute to understand until i saw your pics what was going on. I have run into the same problem, but with the .224 Lee six cavity mould/boolit design. Thanks for posting; the .22 cal checks are tiny in my fat paws and I am gonna try this as it looks as if it might be a solution. I think NOE makes a check expander but this may be the way to get by without one.

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NOE does makes a tool that presses the gas checks on. It uses Lyman style sizing top punches that match the bullets nose profile.

I was lucky that my seating stem was a close enough match to my boolits nose profile. If it hadn’t been I could have used epoxy putty to create a proper seating stem to boolit nose interface.

I hope this method works for you. I’m happy with my results.

JM

Great idea. I used an old die that I put jb weld in with an oiled top punch (to change them out) and do the very same thing.