DoubleStar Inc is located here in Winchester KY. I have 2 DPMS, a RRA and 2 DoubleStars. Fit/Finish on the DoubleStars are perfect (much better than the DPMS, on par with RRA) and haven't had a problem with either of them yet. Owned them for about 2 yrs and several thousand rounds through each. Neither have chrome lined barrels, but that doesn't bother me much.
I believe KYTechMike is correct about the J&T parts, except for the guts--they're all Colt IIRC. The only thing I don't like about 'em is the goofy DoubleStar logo on the lower receiver