In 2012, AR-15 designer Jim Sullivan applied for a patent for a new rifle design. Apparently based on his Ultimax 100 light machine gun, the rifle features a quick-change barrel, a guide-rail-less receiver with a “backbone” guide rod attached to the lower receiver, a modular trigger pack, and dual firing modes in the open and closed bolt positions.

The rifle carries over elements from many of Sullivan’s other projects:

• The unified machine gun/rifle concept from the Stoner 63
• The Stoner-Johnson bolt of the AR-15
• The quick-change barrel and basic operating mechanism and construction of the Ultimax 100
• Open bolt full auto/closed bolt semiauto operation shared with the Ultimax 100 Mk. V and later, and Sullivan’s modified M4.
• Utilizes the Sullivan-designed Surefire 60 and 100 round magazines

In this way, it’s a quintessentially “Sullivan” design:

Image from the Sullivan rifle patent, showing the closed bolt/open bolt trigger mechanism.

There’s no doubt in my mind that the design is well thought-out; Sullivan is perhaps the most accomplished small arms designer alive today (and hopefully will continue to be for many years to come), having had a hand in several iconic and popular rifle and machine gun designs, such as the Mini-14, Stoner 63, Ultimax 100, Ruger M77, and most famously the AR-15. It would be very exciting to see this rifle enter production and – of course – I’d love to shoot it!

EDIT: Commenter mechamaster has posted a link to a prototype of this rifle (apparently called “MGX”) being test fired by Sullivan’s company Armwest. The video, embedded below, shows the weapon firing 100 rounds of 5.56mm ammunition, changing bolt and barrel assemblies, and the firing 100 rounds of 6.8mm ammunition in less than 53 seconds total: