The TAVOR itself had gone through some trials and had been in use with more than a few nations. So you can expect some of the big issues had been sorted out and the technology has matured to certain degree. Cannot say that for the XCR, if my understanding of Robarm is correct, it is made by a small shop with limited money. The whole thing is an on-going beta testing program. In a way, it is really not fair to the XCR. You cannot really use the standard of a military rifle to judge a system that is more or less marketed purely as a consumer item. In a way, if you like it -go buy one. However, if you try to elevate the XCR to a "combat" proven system, you just set yourself up for disappointment.