Remington now markets what they call 'CBees' in .22Long Rifle; a 33gr. truncated cone HP bullet @ 740fps. These should fill up a chamber pretty well. They also make their 'Sub-Sonic' in LR which work really well for me, but Im in the country.
I have the Sportster barrel with open sites for fun/plinkin', if I were going to snipe little varmints I'd have a scope for sure.
BTW, I have shot .22CB Shorts in it and didnt have any trouble, but a youngster might. If the rim slips past the extractor and it gets slammed shut it could go off without the breech locked.