gotcha (I'm too cheap for a decidated .22 upper for now); I tend to do a full clean after most shooting, but was honestly curious as to how much junk gets past the .22 conversion.
The .22 conversion shouldn't affect the chamber at all. The end of it replaces the chamber with basically a hollow .223 shell casing.
I have a cmmg dedicated upper and like it. You can build one fairly easily since the don't require a gas system.