Gas check dimensions for Lee C358-158-SWC? Don't have mold yet to try.

Never have cast or reloaded gas checked slugs, but want the advantage of them in my Ruger 77/357 carbine and GP100 revolver in higher velocity. I've ordered the mold, but am unsure where to buy the checks. Found "DJ's Gaschecks" and Sage Outdoors online (any vendor here make and sell checks too maybe? That was my first hope), but understand there may be a need to determine size of the bullet's base rebate against the size of the check before buying. What size difference do I need? I'll be sizing and applying checks using my Lee press and sizing die, and tumble lubing as learned here. Unsure about aluminum vs copper checks too--only found a few threads about the newer aluminum checks. Sure would, as before, appreciate guidance as to how to proceed. I've scanned two pages of thread hits from a search here, but didn't find this information. Hope I'm not just recovering old turf. Thread links appreciated.Thanks as always. Don.
* Placed a note in another thread to explain my long absence from the forum. Hoping to be welcomed back into the fold.

I don't have the mould you mention, but I do have 3 other Lee moulds in that calibre and all brands of checks fit well. In regard to Copper vs Aluminium, I think price is the big decider, I now use Aluminium checks and find them to be very good indeed and much cheaper. I will say that the Gattor checks I used are one of the best fitting checks I have used. Regards Stephen

Thank you so much. I hope t have the mold and be casting later this week. Must order the checks as soon as I can. Don.

I have a Lee, six cavity, 358-180RF that I use Hornady gas checks with and the work fine. I anneal all gas checks.

I hope you have better luck with that bullet in your 77/357 than I did. My C358-158-SWC mold drops COWW alloy boolits at 0.3575" - 0.358" and my Ruger's throat starts at 0.3615". They went everywhere except my POA. Got a NOE 360-154-WFN GC AN1 recently and am hoping for better results with boolits from it.

I make my own aluminum checks work fine if you have a mold designed for a check. However for handguns and carbines, I would have suggested you get into to powder coating instead and save the money on gas checks because they are not needed when you powder coat. Also the coating can increase the diameter if a mold is dropping undersize.

The gas check shank can be way out of wack with your gas checks, this dimension can be machined wrong on most any makers molds, although maybe a little more common with Lee. Noe offers some inexpensive products to flare bullet base and/or seat checks that don't fit right.