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

Akron Nov12 2026 Lede1
Akron Nov12 2026 Lede1

Collegiate Rifle: Akron Turns Up the Heat in Fairbanks

Akron sets two school records in Alaska as the red-hot Zips climb to No. 9.

Peterson Crushes DMR Field, Wins 2026 Gas Gun Show Series Finale

Scott Peterson won the overall and DMR titles at the Gas Gun Show Series Finale in Oklahoma while Kalani Laker took Recce.

Collegiate Rifle: VMI Shatters Six Program Records in Win Over John Jay

VMI broke six program records against John Jay, led by a 4623-233X mixed aggregate and Darian Tweedell’s school-record 593-41X in air rifle.

Geoff Bushelle Wins Third Illinois F-Class State Championship

Geoff Bushelle fired a score of 1000-79X to win F-Open and Mike Catena topped F-T/R at the 2026 Illinois F-Class State Championship.

New: Springfield Armory Echelon 4.0FC Comp 9 mm

Springfield Armory’s new Echelon 4.0FC Comp 9 mm handgun combines a full-size grip, compact slide and integral compensator.

Familiar Faces, Fresh Records: 2001 National Matches

The 2001 National Matches saw Brian Zins continue his pistol dominance, David Tubb win a record ninth high power title and Gallagher earn a third long-range crown.



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