Leroy James Sullivan (June 27, 1933 – September 22, 2024) was an American firearms inventor. Going by Jim Sullivan, he designed several "scaled-down" versions of larger firearms.
Early life Sullivan was born on June 27, 1933, in Nome, Alaska. Sullivan lived in Nome until he was seven years old, concerned that World War II would spread to Alaska, Sullivan's family moved to Seattle, Washington.
Education Sullivan attended the public schools of Seattle, and later in Kennewick, Washington. Sullivan went on to study engineering, for two years, at the University of Washington in Seattle. Aware that he was about to be drafted to fight in the Korean War Sullivan wanted to become an Army diver, so he left the University of Washington to attend the Sparling School of Deep Sea Diving in Long Beach, California.
Military service Sullivan served in the US Army, from 1953 to 1955, although he was trained by the Army to be a telephone installer and repairman. Due to his civilian training he went overseas to Korea in 1954, where he was assigned by the Army to be a diver to repair oil pipelines and other facilities damaged during the US invasion of Inchon Harbor.
Small arms designer Sullivan is largely responsible for the Ultimax 100 light machine gun and the SureFire MGX. He also contributed to the Ruger M77 rifle, M16, Stoner 63, and Ruger Mini-14 rifles (scaled from the AR-10, Stoner 62, and M14 rifle respectively).
Armwest LLC M4 In 2014, Sullivan provided a video interview regarding his contributions to the M16/M4 family of rifles while working for Armalite. A noted critic of the M4, he illustrates the deficiencies found in the rifle in its current configuration. In the video, he demonstrates his "Arm West LLC modified M4", with enhancements he believes necessary to rectify the issues with the weapon. Proprietary issues aside, the weapon is said to borrow features in his prior development, the Ultimax. Sullivan has stated (without exact details as to how) the weapon can fire from the closed bolt in semi-automatic and switch to open bolt when firing in fully automatic, improving accuracy. The weight of the cyclic components of the gun has been doubled (while retaining the weapon's weight at less than eight pounds). Compared to the standard M4, which in automatic fires 750-950 rounds a minute, the rate of fire of the Arm West M4 is heavily reduced both to save ammunition and reduce barrel wear. The reduced rate also renders the weapon more controllable and accurate in automatic firing.
Armwest/SureFire Advanced Rifle Operating Core (AROC) In 2012, Sullivan filed a patent for a modified operating "core" for the M16/M4 family of weapons. It was dubbed the Advanced Rifle Operating Core (AROC) and featured several changes to the TDP specifications. The AROC consists of a new upper receiver, including bolt carrier group, as well as action spring and buffer, all of which can be used with existing lower receivers. The AROC bolt lugs are 30% longer than the TDP spec, making them twice as strong as a standard mil-spec bolt. Although requiring a longer proprietary barrel extension, the longer barrel extension reduces the steep feed ramp angle as found on a standard M4, for smoother and more reliable feeding of ammunition. The AROC bolt carrier has an additional .400" of travel into the receiver extension requiring a shorter buffer. Along with the additional bolt carrier travel, there is a spring loaded weight in the rear of the carrier that acts as a counter weight to increase dwell time, reducing the cyclic rate to 590-610 rpm depending on ammunition. This makes the weapon easy to control on full automatic fire, increasing accuracy and effectiveness of the weapon. The AROC's Bolt also has a set of interlocking inconel gas rings that are effectively indestructible in the context of the weapon's service life. The AROC also has a heavy duty gas tube to handle full automatic fire. The delayed unlocking of the bolt reduces carbon fouling allowing the AROC to fire thousands of rounds without cleaning or lubrication. In 2016, Sullivan licensed the AROC's bolt carrier group technology to SureFire as a drop-in upgrade for standard AR-15 pattern rifles. Sold as the SureFire Optimized Bolt Carrier (OBC), it features the modified cam path, gas key, and proprietary buffer system of the AROC. However, it lacks the longer bolt lugs and inconel gas rings. In 2017, Sullivan write a letter to then Commandant of the U.S. Marine Corps, Robert Neller offering the AROC to the USMC. This was in response to an article published by the Marine Corp Times in which Neller expressed interest in finding improved infantry rifles to replace the M4. In the letter, Sullivan promoted the AROC as a single weapon to replace the M4 Carbine, M249 SAW, and Heckler & Koch M27. Along with the letter, Sullivan included a DVD showing relevance and proof to his claims. In 2020, SureFire partnered with Geissele Automatics to make a weapons platform combining the AROC operating system with Geissele's 'Super Duty' rifle. In 2022, the joint SureFire-Geissele AROC rifle was reportedly selected by the U.S. Army's Delta Force to replace their inventory of Heckler & Koch HK416s. However, due to contract disputes between SureFire and Geissele, the rifles were never delivered. The SIG Sauer MCX Spear LT, which was the runner-up in the competition, was selected instead. In 2023, SureFire adapted the design principles from the AROC into the creation of the Intermediate Combat Advanced Rifle (ICAR), an AR-pattern rifle chambered in 6mm ARC. Unveiled to the public in 2025, the ICAR is reportedly undergoing test and evaluation by Joint Special Operations Command as part of a medium-range assault rifle program. Much like the AROC, the ICAR features longer bolt lugs, barrel extension, and a modified cam path. This effectively eliminates the issue of stunted bolt life seen in drop-in 6mm ARC bolts for commercial off-the-shelf AR-15 rifles.
Death Sullivan died on September 22, 2024, at the age of 91.
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