I've used TWO gas checks over and below a charge of shot to create a shotshell load in pistol. There really isn't anything special about what Eld suggests. I think he's got a good idea and for dang sure the gas check WILL come out the barrel with everything else when the fires starts. It couldincrease pressure a tiny amount but such a combination wouldn't be used in anything like a maximum charge to begin with...so this is really a non-issue.
I'd like to add that the HARDNESS of a cast bullet is not a guarantee of it's "leading properties." I've seen rather soft bullets driven like a bat out of hell and cause zero leading and conversely some really hard cast bullets that just paint the inside of a barrel with lead from the same or even milder loads.
If I remember correctly TIN melts at a lower temp than even lead. What bullet leads and what won't is, I'm convinced, about half witchcraft.
