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Marine Spacer Tube - Mossberg 930
Competition Forearm Retainer - Mossberg 930
Enhanced Competition Follower - Mossberg 930
Competition Spring Plunger - Mossberg 930
Enhanced Bolt Release - Mossberg 930
Competition Part Combos - Mossberg 930

Competition Parts - Mossberg 940

Glock Sight Saddle - Mossberg

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OR3GUN™ Marine Spacer Tube for Mossberg® 930/935

The OR3GUN Marine Spacer Tube (MST-930) for Mossberg 930/935 series shotguns is a major enhancement to the reliable function of your firearm in all weather conditions.

Natural Habitat Application Comparison Color Price Status ORDER



Sporting Clays

Light Weight
(2 & 3/4 Loads)

Bright Color
(Comp Ready)

Marine Blue
$49.95 In Stock

Gun Sports



OEM Weight
(Magnum Ready)

Teflon® Finish
(Easier to Clean)

Storm Gray
$54.95 In Stock

For years, competition shooters like ourselves have battled seemingly random cycling malfunctions with the gas systems in Mossberg's 930 series. This has been a point of personal frustration for most of the OR3GUN team, as we invested heavily in the 930 platform due to the reasonable cost of running duplicates and the 'lefty friendly' nature of the guns. Our products are not only the solution for many of these frustrating cycling issues, they are the first to acknowledge there is a problem that needs to be addressed in the first place.

OR3GUN Marine Spacer Tube

The OR3GUN Marine Spacer Tube replaces the Mossberg OEM ‘Gas Piston Spacer Tube’ (located inside the forend) during the course of a normal shotgun cleaning. This OEM spacer is where you typically find a buildup of carbon fouling, dirt and in many environments, water. Moisture from humidity, condensation, dew point and precipitation is the often ignored component in the 'random' malfunctions experienced with the 930 platform. Most people don't think to consult their local meteorologist to help troubleshoot their shotgun. In addition to the functional issues created by the changes in weather conditions, often times the resulting moisture is only discovered hours or days later when it has also begun to corrode the magazine tube.

Sample of Typical 930 Magazine Tube Corrosion

The factory OEM spacer tube exists only to passively transfer the energy of the gas piston to the pusher assembly. Mossberg utilizes a tightly fitted aluminum tube over the existing steel magazine tube. A number of unforeseen problems are set in motion by this component as humidity and round count can conspire to slow the cycling of the gas system to the point of malfunction.

The MST-930 was engineered to be an active component in keeping your gas system functioning at peak reliability. This was accomplished by designing an entirely new part with a carefully engineered feature set. This cutaway of one of our original production prototypes highlights some of these features in detail.

OR3GUN Marine Spacer Tube Cutaway

A relief is incorporated within the center section of the tube in order to minimize contact between dissimilar metals, greatly reducing the amount of condensation formed. This relief also reduces contact of friction surfaces by more than 75% for smoother cycling. In addition, the oversized outside diameter of our Marine Tube is stronger and more durable while the Marine Blue Competition version is engineered to be lower in overall weight for faster cycling shot to shot. Our Multi-Use version is OEM weight to properly buffer Magnum Slugs & Buckshot.

A matrix of holes in the relieved center section of the tube allows transient gas pressure to actively expel moisture, carbon and dirt during normal cycling of the gas system. The holes also allow the part to vent while cooling, greatly reducing trapped moisture which can lead to corrosion if cleaning is delayed.

OR3GUN Marine Spacer Tube Contact Points

The end sections of the tube are the same inside diameter as the OEM part, creating narrow contact rings that squeegee the buildup of moisture, carbon fouling, dirt and excessive lubrication from the magazine tube. This debris would otherwise form slurry and slow the OEM part through hydraulic friction or resistance. Instead, this debris comes to rest inside the plastic forend of the shotgun where it harmlessly awaits the next regular cleaning. Each ring is designed so that it will travel further than its length during cycling for the most effective shedding of debris.

The anodized finish of the OR3GUN MSTs help protect the parts themselves from corrosion and is resistant to flaking, chipping or peeling over the lifetime of the component. The finish also enhances the durability and efficient heat-transfer properties of the MST. Our new Storm Gray Multi-Use version additionally features a proprietary Teflon coating that greatly eases cleaning of the part and reduces friction even more.

If you still aren't convinced that our Marine Spacer Tube is a necessary component for a reliably cycling 930, take a look at the new 940 JM PRO from Mossberg. See any gas system improvements that look familiar? Don't let your 930 go another day without our Marine Spacer Tube.

Check out our classic YouTube video, detailing one of the common problems that can be fixed by installing the OR3GUN Marine Spacer Tube in your Mossberg 930 Jm-Pro.

The OR3GUN Marine Spacer Tube for Mossberg 930/935 series shotguns is an active component in keeping your gas system functioning at peak reliability.

Due to the maze of ITAR and export regulations on firearm parts, only a specific few of ours are currently for sale outside of the United States to select countries. As most non-combat shotgun parts are exempt from ITAR and conform to the EAR99 category for export, we have begun selling specific combinations of our parts to customers in Canada, Germany and the United Kingdom. If you reside in one of these countries, please make your purchase from our International page only. International orders generated from elsewhere will be cancelled. While shipping charges are calculated and included when you complete your purchase, localized customs fees may be levied at the destination.

Mossberg®, 930, 935 and 940 are trademarks of O.F. Mossberg & Sons, Inc. All rights reserved.
OR3GUN™ and The OR3GUN Project™ are trademarks of Logistix Productions, Inc. All rights reserved.
Specifications are subject to change without notice.