Stan, the center short 10 lifter breech walls are not as thick as the Quality D lifter to its left because the D is a 4 frame.

Excellent ! I tried a bunch of ways to fit a disc/wafer in the bottom of the old brass hulls so they’d work well with smokeless and pretty much had no luck .

#4 frame #1 frame comparison:
 

Not a fair comparison, this is a Quality G 12 gauge from 1888. It’s a #1 frame.
I’m not sure if #1 frame 12’s are common but it’s very petite compared to the #4 frame 10.

Craig, can you explain the "web" and the need for a disc or wafer to make a brass shell work well with smokeless? What kind of brass shells can we use with smokeless? Is there a safety situation?

To me, it’s a simple aspect of the shell manufacturers business philosophy to sell shotgun shells. Why would they recommend the reuse of all brass cases when they can be reused indefinitely. That would not be a sound business model.
Has anyone ever worn out a 45 ACP brass? I didn’t think so.
As a side note I measured the head thickness of the Parker Bros reproduction brass at approximately 1/8”. In contrast, the balloon head imported 12 gauge all brass case measured approximately 1/2 the thickness of the Parker repro brass.
I also believe the “disk” in the head of modern shells is a protective measure to cover junction of the plastic case wall and the brass head.

A couple of points: What brand are these "imported" brass cases you mention? What brand are the "reproduction Parker" cases? What brass cases are suitable for using with smokeless powder? Are my beautiful Rocky Mountain Cartridge cases suitable for smokeless powder loads? If not, why not?

Magteck are the imported ones from Brazil. I have those in 16 and 12 gauge. They aren’t the quality of the TOW or RMC.
https://www.ballisticproducts.com/Br.../products/202/
Track of the wolf Parker reproduction brass:
https://www.trackofthewolf.com/Categ...-shell-10-2-58
Bill, your Rocky Mountain brass, as you know are top quality.
I don’t know why smokeless powders are not recommended for brass shells.
Like you, I would like to know.
I have shot and reloaded countless brass shells with BP and they have always worked flawlessly.

I have read of the brass shells cracking sometimes from the pressure of smokeless powder. I would assume that is probably more of an issue with the cheaper Magtech brass.

Smokeless Brass Shotshells
 

Factory examples of smokeless brass shells.
Note: These are Not Damascus friendly, however, with the proper amount of powder and velocity perhaps they could be safely used. I would never use a roll crimp.

Impressive group Bruce.