While we were at the gigantic and bustling SIG Sauer booth checking out the MCX/MPX rifle family, the SIG rep hinted that we might want to goover to the suppressor display and talk to the wizard behind thecounter. We were introduced to none other than John Hollister, a legendin the suppressor world and one of the co-inventors of the .300 Blackoutround.
At one point during our impromptu but fantastically informative15-minute master class on suppressors and internal ballistics from theSuppressor Gnome himself, he got a mischievous expression on his faceand suggested that we would be interested in the hardware beingdisplayed in a low-key way at the back of his counter. He was excitedto show us how the MCX upper, which does not require a standard ARbuffer tube, was direct-fit compatible with conventional AR lowers.
SIG will be offering a complete MCX upper conversion kit in .300Blackout with an integrated (not integral) pinned-and-welded SIGsuppressor, coming in a 16.1 inches barrel length. This makes it asingle tax stamp gun, reducing cost and making it legal in jurisdictionswhich permit suppressors but prohibit SBRs. Interestingly, theconversion kit also includes a SIG folding stock to mount in place ofthe buffer tube, something which normally costs at least $200 toretrofit to a conventional AR.
Hollister explained that the 300 Blackout round was designed tocompletely burn its powder charge in only 9 inches of barrel, comparedto the 5.56 round which was designed and optimized for the 20-inchbarrel of the M16A1. This means that the MCX integral suppressed upper,despite having a relatively short barrel behind the suppressor, willshoot cleanly and reliably at full-rated velocity with both subsonic andsupersonic ammunition.
The SIG MCX integral suppressor complete upper kit is expected to becommercially available in the first half of 2019, with pricing to beannounced.