In answer to a question posted by Fly both here and on AR15.com (BTW, Sorry I didn't see that post on here.), yes, the XCR will function without a recoil buffer. In fact, on a low gas setting, the buffer isn't even touched. If you fire your rifle without a buffer, you will experience an increased kick, and depending on the gas setting, you could even damage your lower a bit. nothing major, but you'd definitely ding parts up. Firing the rifle without a recoil buffer installed isn't a good idea, and we don't recommend you do it. These words are straight from the mouth of the guy who designed the XCR.