I dont know about TSE, but I know Epps and Wolverine, at the top of the page have them,supporting dealers as well. Or you can just call TSE. I went with the .223 upper because I can utilize my mags(Pmags, LAR, GI). I think you can only use Cproducts mags with the 7.62, of which I detest and had only complete failures with the .223 one. I could be totally wrong as I have not bothered looking into a 7.62 upper.It is something worth looking into. Mag availability is tops for me. My cz is for the bulk cheap sh!t corrosive milsurp. Buy it from a reputable dealer, I believe Wolverine is the source and heard great things about them fixing XCR complaints. I hope to not have to send mine to them. I have 600 rnds through mine and nothing wrong except said garbage mag. I just tightened all the bolts up when i first got it, no loctite yet, and it seems to hold for now. Its a great gun. (maybe not a combat first choice)lol. And dont listen to the haters that are assuredly ready to chime in. Good luck....
Ohh I dont want to make it seem like a problematic rifle, but some new designs go through teething issues, I have heard better reciews of the newer versions of the XCR versus initial run offs. QC seems to have improved.