In addition to what Doug commented, I found that at about every 500 rounds or so the .22 chambers are gummed up. Use JB bore and use a good brass brush and chuck up in a power drill. Only work the chamber area. Be sure to clean out the JB. .22's build up a shellac that is pretty tough. Simple cleaning solutions aren't strong enough. Hopes this helps, .22's build up a lot gunk.
art mc.