I have a late twenty's standard 16 auto-5 short chambered that I have used the rst stuff in. Seems like it's good stuff. I also save some damaged crimp hulls that still have good primer pockets for whenever I decide to load for it. Just hasn't happened yet, kinda fell to the side.
Bismuth is a great answer for older shotguns. I have been using Hevi-Bismuth Upland in a vintage 20 gauge that I was given. The 5 shot is deadly on pheasants and it great to able to use such a classic shotgun again.
Honestly, I am able to shot with the 12 gauge boys thanks to the Hevi-Bismuth.