Years ago, Kevin, the CdA Muzzleloaders enacted a rule that limited shooters to .58 caliber.
It kinda irked me, as I really enjoyed shooting my .62, but rules be rules, so I always shot their shoots with my .54.
Ironically, the only one of their silhouettes that I ever broke was a rabbit
- wait for it -
with that .54 loaded with 85 grains of Ffg.
If you are shooting 20 ga smoothies, me thinks that rule has been long forgotten. I would guess it was voted on in 2006 or maybe 2007. It might be good to ask about it and see if anyone remembers that, beside me.