Gbro, yeah, the plastic cups.
Y'know, I've never checked for a short chamber. !!! I'd have to get it from the safe and check to see what it says on the barrel, if anything. However, no problems during several cases of ammo, so odds are "It's not that old!"
I also have a 1913 vintage Model 12; 20-gauge. Looks like 3/4 size of my 12. I had its chamber reamed for modern shells. It, too, is FC and shoots tight patterns.