Preview: JP Variable Mass Operating System

by
posted on October 19, 2016
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
vmos-a.jpg
JP Enterprises new Variable Mass Operating System (VMOS) bolt carrier enables rifles to be easily tuned for a wider range of applications, such as suppressed rifles or exotic calibers.

"There's no such thing as 'one size fits all' in AR operating systems," states JP founder John Paul. "Tuning your rifle is the only way to realize its potential and provide the performance you want. That's why we pioneered the adjustable gas block concept more than two decades ago. Tuning can be the difference between reliable function and reliable frustration."
null
JP says, "The VMOS bolt carrier ensures reliable function, especially for systems without an adjustable gas block."

Like JP's other carriers, the VMOS models increase bearing surface. The cocking pad is longer, and exterior bearing surfaces are polished before the carrier undergoes a multi-vendor QPQ (Quench-Polish-Quench) process.

The VMOS is available now for large-frame (.308) AR-type rifles starting at $319.95. This standard version of the large-frame VMOS carrier includes three steel weights. Two weights can be exchanged for heavier tungsten ones. JP plans to release a small frame (.223) version early next year.

Latest

2026 Usashooting Jrriflechamps 1
2026 Usashooting Jrriflechamps 1

Preview: 2026 USA Shooting Rifle Junior Olympic Championships in Alabama

The 2026 USA Shooting Rifle Junior Olympic Championships kick off this week in Alabama with athletes competing in both smallbore (50m) and air rifle (10m) events.

New: Springfield Armory SA-35 4" Model

Springfield Armory’s SA-35 4" pistol chambered in 9 mm Luger offers all the benefits of the original SA-35, plus a shorter, more compact barrel. 

Federal All-American 20-Gauge Target Loads Now Shipping

Federal Ammunition’s All-American competition shotshell line is now shipping in 20-gauge with two new target loads in No. 7.5 and No. 8 shot at $15.99 per box.

NRA America’s Rifle Challenge: Three Divisions of Competition

Ryan Muller walks through the optics, accessories and caliber rules that define NRA ARC’s Stock, Limited and Open divisions.

Registration Open for 2026 NRA National High Power Long-Range Championship

NRA High Power Long-Range Nationals return to Alliance Rifle Club in Malvern, Ohio, with five days of competition at 800, 900 and 1,000 yards.

The Hand Cannon: The First Handheld Firearm

ARTV explores the hand cannon—the first handheld firearm in Europe—from its documented origins around 1326 through three distinct types to the eventual development of the matchlock.

Interests



Get the best of Shooting Sports USA delivered to your inbox.