Some years back, I wanted to shoot unsized bullets, with a gas check.
What I did, was drilled an old set of pliers that had a wire cutting attachment on the side.
I clamped the pliers shut in the vise, and drilled it in the middle of the wire cutters to the diameter of a properly crimped gas check. I figured it wouldn't work, that I'd never get it centered, but surprise, it worked very well.
The hardest part was making sure that the gas check was straight on the bullet before crimping.