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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™ Competition Spring Plunger for Mossberg® 930/935

The OR3GUN Competition Spring Plunger™ (CSP-930) for Mossberg 930/935 series shotguns assists in the reliable cycling of the lightest possible loads in competition or field environments. The companion Adjustable Spring Retainer™ (ASR-930) line allows for additional fine tuning of spring rate at the other end of the recoil assembly.

Natural Habitat Application Features Color Price Status ORDER



Spring Capture
(Maintains Geometry)

Light Loads
(Lowers ESR ~ 10%)


Marine Blue

$27.95 In Stock

Gun Sports


Spring Capture
(Maintains Geometry)

Magnum Ready
(Lowers ESR ~ 5%)


Storm Gray

$28.95 In Stock

Gun Sports


(1 Lighter, 3 Heavier)

Fixed Setting
(R&R Buttstock)


Marine Blue

$25.95 Low Stock

Gun Sports


(1 Light, 1 Heavy)

Quick Change
(R&R Recoil Pad)


Damp Earth

$28.95 In Stock

The OR3GUN Competition Spring Plunger (CSP) replaces the factory plunger in your 930’s recoil spring assembly. Utilizing your factory spring, our CSP’s refined dimensions result in a reduction of the recoil system’s Effective Spring Rate for more reliable cycling of the lightest competition loads. The CSP’s unique tail design provides partial capture of the recoil spring to both improve recoil assembly geometry and help prevent scoring of the recoil tube wall. The CSP installs in the recoil spring tube inside your stock and interfaces with your bolt carrier link.

OR3GUN Parts in Blue (Trigger Group Removed)
(Trigger group removed to show relationship of parts in a Mossberg 930.)

The companion Adjustable Spring Retainer (ASR) replaces the factory return spring retainer in your recoil spring assembly. Depending upon which position the ASR is secured by the factory pin, your spring rate can be further lowered or can be adjusted back up to allow tuning for the variety of loads you need to run in your gun.

OR3GUN Adjustable Spring Retainer

In competition guns, there is a delicate balance between load weight and reliable cycling. The factory 930/935 is designed to run loads as heavy as magnum buckshot and turkey loads. If the competitor is willing to give up some of the heaviest end of the load spectrum, ground can be gained in the lighter end.

12 Gauge Load Shot Weight Velocity Power Factor
Low Recoil Target 7/8 Oz 980 FPS 375
Low Recoil Slug 1 Oz 1200 FPS 525
Light Target 1 & 1/8 Oz 1145 FPS 564
Bulk Field & Target 1 & 1/8 Oz 1200 FPS 591
Super-Handicap 1 & 1/8 Oz 1250 FPS 615
Super Sport 1 & 1/8 Oz 1300 FPS 640
Standard Slug 1 Oz 1600 FPS 700
High-Brass Field 1 & 1/4 Oz 1330 FPS 727
Magnum Slug 1 Oz 1760 FPS 770
Magnum Turkey 2 Oz 1300 FPS 1138

While a Marine Spacer Tube equipped 930 has a broader selection of shell types that will reliably cycle, not every gun will consistently cycle the same light loads as others. While some of this is due to barrel length (and ‘dwell time’), tolerances and build quality from gun to gun are the biggest factors in how light of loads each specific gun will ultimately cycle.

In addition to gas system issues, the OEM method of mating the factory return spring to the factory return spring plunger has caused scoring of the plunger and recoil spring tubes in some guns. The resulting drag of the assembly will also affect proper cycling of light loads.

OEM Spring & Plunger Fitment OEM vs OR3GUN Spring & Plunger OR3GUN Spring & Plunger Fitment

Regardless of the tolerances of your gun's build, some of the lightest loads simply cannot generate enough gas pressure to cycle the OEM parts in the gas and recoil systems against the weight of the factory springs. Cycling the extreme 'power factor' spread of 12 Gauge shot shells is a challenge not asked of any other single caliber platform.

OR3GUN Competition Spring Plunger

The OR3GUN CSPs are CNC machined from 6061 T6 Alloy. The unique tail captures and guides the spring in addition to producing an effective spring rate reduction equal to cutting 3 coils from the factory spring for the Competition version. The spring weight reduction in our testing of the Competition CSP was found to be nearly 10% in all guns. (Trigger groups were removed for isolation of the recoil assembly.) No modification is required to the factory spring and the plunger can be changed as simply as detail cleaning the recoil system.

The Competition version may be just what your MST equipped gun needs to cycle the lightest loads reliably, turning those all clays stages into lighting fast runs while still maintaining the ability to reliably run 1300+ FPS bird shot and standard slugs in other match stages with the same set-up. When paired with the Competition ASR, the effective spring rate can be incrementally adjusted to fit your particular load range.

Competition vs Multi-Use Comparison

The Multi-Use version of our CSP was created to meet the demands of those wanting to run magnum loads, yet gain the benefits of the refined spring capture. The Multi-Use Plunger has an effective spring-rate reduction of only 5% at the peak tension. It is also slightly heavier (~10%) than the OEM part to better buffer magnum loads during the entire recoil cycle. This is the plunger for those running a steady diet of full power loads through their shotgun.

Plunger Model Part Weight Effective Spring Rate w/ Matching ASR
OR3GUN Competition 13.2 grams -10% average 0%, -5%, -10%, & -15%
OR3GUN Multi-Use 15.0 grams -5% average N/A
Mossberg OEM 13.5 grams N/A N/A

The Field ASR (Quick-Adjust) is for those running two distinct types of loads (hunting/practice) through their 930/935 in different sessions with time between to change the setting. When used with a Multi-Use Plunger, the spring pre-load can be changed from -10% (for light field loads) to full OEM weight (for slugs and turkey loads) by simply removing the shotgun's recoil pad (two screws) and turning the setting with a small punch or the tip of a pen.

OR3GUN Field CSP/ASR Set OR3GUN Field ASR Animation OR3GUN Field ASR - Quick Adjust

Check out our CSP YouTube video, detailing the 930/935 recoil spring assembly maintenance.

Due to the maze of ITAR and export regulations on firearm parts, those on this page are not currently for sale outside of the United States.

Mossberg®, 930 and 935 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. Spring rates are averages in properly lubed guns with new factory springs and are rounded to the nearest 5%.