Is it necessary to have a die to seat Gas Checks?

[Tackleberry41]

I tried doing it without a sizer. Just mangled a case, you could watch the gas check wallow out the neck. Annealed ones might not do it. It was $20 for a lee sizer. Tho like alot of Lee stuff does need some work to do a good job. Out of the box it tends to put gas checks on crooked if you get in a hurry.

[kweidner]

I've tried what Dean Winchester was talking about, and I agree, it is a PITA. I used a foam plug to keep the bullet from falling through so it only crimped the GC.

A whole lot easier to get a lee push through sizer in the size you want to end up and use that to crimp on the gas check.

They don't seem to make a .312 (and custom's cost a lot more) so I'm using a .311 and it hardly touch's the bullet.
Normally just a couple of shiny spots on the driving bands. I am considering a custom sized .312 sizing die, maybe next year.

Real easy to make a .311 a .312. Get you some 400 grit wet dry sandpaper, a split wood dowel 5" long and chuck it up in a hand drill. The longest part of the process will be cutting sandpaper the right length to just fit in die when wrapped around the dowel rod. Spray paper with something like rem oil. Chuck die in vise held with your casting glove. Drill on medium speed with an in and out motion. The entire process may take ten minutes. Go slow and size one after about 5 laps in and out. Repeat until your boolit sizes the diameter you want. I purposley order my lees .001 under and lap to diameter I want. They are much smoother this way.

[26Charlie]

You may need both. For the 8x56 Hungarian, I cast, gas checked, sized and lubed .338 Lee bullets, then ran them though a Lee custom .330 push through die. Lee now makes a .332 die for this caliber, but then it was a custom item.