This is #1 of the two 5.45 barrels US MGA asked me to make, #2 is currently waiting on backordered blanks. They are using M27 links, but they did make a simple machine to expand them so the belt wouldn't be too stiff. I had to bore out the bolt face about .020 and they had to make some adjustments to the feed tray, but other than that - pretty strait forward. The barrel I made using a true 5.45 blank from Green Mountain, gas block and extension was reclaimed from a standard 18" barrel. Bolt is a true MK46 with the hard chrome treatment, supposedly made for the seals or something, whatever - nice bolt though for sure. It's 17" long, 1/2 X 28 muzzle threads, not much else to it. I am also making a couple in 6.8 SPC2 and one for me in 6.5 Grendel, both of those will feed from RPD belts with the conversion package the MGA already makes for their 7.62 x 39mm kits.