A SIG MCX-SPEAR LT bolt and recoil spring assembly ... Unlike AR-15 designs, which require a fixed receiver extension to house the buffer and recoil spring, a design like the MCX that follows ...

the MCX VIRTUS utilizes the proven SIG Sauer short-stroke piston system and unique internal recoil system that eliminates the M4-style buffer tube. The result is a compact, light-recoiling ...

Hot off its new contract with the U.S. Army, Sig Sauer has ... s popular line of MCX gas-operated piston AR-15-style rifles. But MCX has the benefit of not needing a buffer tube in the stock ...

The MCX has a more AR-18 style layout, which allows for a folding stock. (The SIG 516 and HK416 does not support conventional folding stocks due to using a traditional AR-15 buffer tube layout.) ...