I tried installing an AEG bucking in mine and the lips from the bucking protrude too far in and block enough of the feed hole for the bbs to cause serious jamming issues. The chamber itself doesn't lock into the gun tight and can be rotaded in the receiver. If you do not put it in correctly, it will jam. I could buy a new Echo1 chamber, but I would rather give the G&P a try if it will fit correctly because I like the way the hop adjuster works. I read that a Classic Army chamber will fit, but I am not sure if the CA and G&P are compatible.