No, but I've shot patched stainless steel ball bearings once out of .56cal. smoothbore just for fun.....
Years ago I had a 69 cal smoothbore. Paint balls are 68. 7 grains of 2F card over powder, soft Kleenex lightly tamped, paint ball, 1/2 Kleenex to stop it from rolling out, good for about 40 feet.
I've seen those nylon balls lying up on the berm and wondered what they were!Forget the "less lethal" thing.
1st, "less lethal" doesn't mean always not lethal. 2nd, in most places if you don't have the right to use lethal force in a situation,,, that does not mean you have the right to use something like rubber bullets.
If you are justified to shoot,,,, shoot for real,,, if not but you do with a rubber bullet, chances are you will be charged just like you shot with real ammo.
I can verify that shooting a ramrod generates a fearsome amount of recoil. Let's just say, I knew a guy who did that one time.Patched marbles'd be my choice. "Cats; Eye" for shooting at night.
Rubber buckshot and 37 mm solid rubber cylinder loads are useful for crowd control. 12 ga. rubber also for chasing critters. Beanbag rounds are effective and pretty accurate, but deadly at close range (won't bounce back, either).
Stuffing stuff into guns other than lead ain't new but results vary widely. When hunting squirrels, a buddy launched his ramrod by mistake. Far as I know, it may still be circling the earth. Recoil bruised his shoulder, missed the squirrel.