I suspect the 60 gr SSS bullet (post # 12) would go too far in the case of a miss, and still be dangerous when it came down. The 20 gr bullet from the Aguila Suoer Colibri sans poudre rounds would not be as dangerous. It is about the equivalent of a #4 buck pellet. Probably not fun to get hit with, but the 60 gr SSS is about the equivalent of 00 Buck pellet, weight wise.
I found the first shot of the SC sans poudre rounds got stuck in a well-worn 18" Remington Nylon 66 bolt rifle barrel, but I ramrodded it out and ran a Boresnake through the rifle and all the rest (about twenty rounds) went through OK.
With a 25" barreled Reminton 512, no shots stuck in the barrel (about 10 rounds) but by then I had gotten smart enough to run a Boresnake through the barrel before trying it.
Both these rifles are "well broken in," having had thousands of rounds through them, so the barrels are pretty smooth by now.
The 60 gr loads seem to have fair accuracy out of my Ruger MK II pistol and do cycle, but have a tendency to not feed well.
The 20 gr loads shot about 3" to the right out of the Nylon 66 at about 30 feet. It is not impossible that this was because the rifle lost its zero at some point in transporting it. Penetration was anywhere from 150 to 200 pages of dry telephone book. Group was about 2", but the scope was not focused for this distance. I cannot find the target for the same loads out of the Remington 512, so I can't give any sighting information on the 20gr loads in that rifle.
In a pistol, even the Super Colibri sans poudre loads give a substantial report... enough to make one's ears ring indoors.
Out of the 25" barrel, the firing pin click is louder than the report, although the little 20 gr bullets do make a smack when they hit telephone books. The 18" Remington makes a moderate "pop," not enough to disturb anyone.
I am pleased to note that the Telephone Company recently was generous enough to leave more free indoor backstop material at my front door for future, more comprehensive, testing
--Terry