Martin- we've been loading 12 bores with round balls using a similar approach but the wad over top of the ball you say the Russians use, if not needed. The cupped wad at the rear centres the undersized ball in the tube as it's being driven down the barrel.

I use a normal folded crimp on my round ball loads, except when using brass cases, which have a heavy handgun-bullet-type crimp to hold the ball.

E-mail Jeff Tanner for any mould size you want. They are not expensive, compared to any other custom mould maker - barely more than Lee moulds & 1/2 the price of a Lyman mould. Lee makes a .690 RB ball mould, btw.

I use .684", .710" and .722" RB's depending on the gun I'm loading for. I use the plastic gas check cut off the bottom of trapsload wads. I puck up wads at the local club, using side cutters to snip off the fingers and shot cups. then, I use normal card and fibre filler wads to the height I need.

Powder in the case, then a hard card or cut-off shotcup gas check on the powder, then filler wads to get proper height, then shotcup gas check, cup-up underneath the ball, then crimp. The cup underneath the ball holds the ball in the middle of the bore as it travels out the tube. Another wad is not needed at the front due to the driving force from behind, holds the ball in the middle of the bore. This is the concept you posted above.