first major manufacturer to offer a 6.8 mm Remington SPC chambered version of the AR-15 was Barrett Firearms Company, offering the Barrett REC7. By 2007, most major manufacturers of AR-15 type rifles for the civilian gun market (including Olympic Arms, Bushmaster Firearms International, LMT, LWRC, DPMS Panther Arms, Rock River Arms, Stag Arms, Ruger, Bison Armory, AR15 Performance, Dedicated Technology, Yankee Hill Machine, Ambush Firearms, Wilson Combat, Daniel Defense, and Remington Arms) were offering rifles in this caliber. Dedicated AR upper receiver assemblies chambered for the round are produced by a number of smaller firms. Ruger Firearms produces a 6.8 mm for their Ruger SR-556 piston-driven AR-15 variant.[17] The Stag Arms Hunter and Tactical models utilize the newer chambers and specified twist rates to accommodate higher pressure loadings. Microtech Small Arms Research offers their version of the Steyr AUG in 6.8. Robinson Armament Co. offers the XCR-L in 6.8, which can be easily converted between 6.8, 5.56, and 7.62x39. Bushmaster offers a 6.8 chamber and barrel along with 5.56 for the ACR also. Ruger Firearms chambered their Mini-14 Ranch Rifle in this round for several years; however, it has been discontinued.