I put about 200 rounds through my 15-22 every week, mostly CCI SV. The chamber does accumulate a carbon ring that can cause malfunctions. I give the rifle a good cleaning every week starting by putting a brake cleaner soaked gun cleaning q-tip in the chamber to soften the carbon. This is followed by brushing the chamber with a 25 cal brush. Even this doesn’t remove all of the carbon so I hit it with the Flexhone every couple of months. By following this cleaning regimen I keep my 15-22 100% reliable.