Thanks for the replies.
I'm wanting commercial thicknesses of gas checks as I use them for 454 Casull and 303 brit. I do already powder coat everything but feel like on these high pressure rounds it's a good idea to have a check in place as well. As far as non gas check bullets, I just powder coat and it's fine so really not concerned due to the low pressures. Seriously, powder coating the best thing since sliced bread when it comes to cast bullets as it keeps everything so clean.
I was thinking about making a cutter in the style of a drilled block of steel and punches. One hole to cut, one to cup. I don't have a lathe so I was trying to figure out something simple that I could build here with ease. Drilling a few holes and using a drill press as a makeshift punch lathe I figured I could make something that gives a close enough size to be usable after running through the sizer. Not the best solution but I've honestly been a bit perplexed by the lack of commercial availability of gas check dies given how many bullets are designed for them.