The barrel on the XCR can be changed just by loosening the barrel bolt. You would have to replace the bolt, barrel and magazine, thet can also be change to 6.8 spc and they are working on 6.5 grendel. I have one in 5.56, wonderful gun. They are currently taking about 6 months if you order one. they have also come out with a pistol version and if you want SBR if you go to the trouble of getting a tax stamp. I blame the members of the forum for making me by mine. If you get one you won"t be sorry. The first time you fire it and there is no sproing in your ear from the ar recoil buffer will make it worth every cent you pay. Go to XCRFORUM.COM or robarms.com.