To pick a nit, "caliber" refers to the bore diameter.
Best choice, to my thinking, is to get an adapter to allow shooting a .22LR in the .223, maybe a second one to dedicate to CB caps?
(Wiki is really getting useful):
http://en.wikipedia.org/wiki/Caliber_conversion_sleeveCaliber conversion sleeve
From Wikipedia, the free encyclopedia
A number of different devices exist whose function is to non-permanently alter a firearm to allow it to fire a different cartridge than the one it was originally designed to fire. These devices are called by many names, including caliber conversion sleeve, cartridge conversion sleeve, supplemental chamber, chamber insert, and subgauge inserts or subgauge tubes. This article will break the various conversions down into types by the degree to which they alter the cartridge used by the firearm.
(Snip whole bunch more good stuff)