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Enhanced Bolt Release - Mossberg 930
Cast/Drop Adapter - Mossberg 930
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OR3GUN™ Cast/Drop Adapter for Mossberg® 930/935

The OR3GUN Cast/Drop Adapter™ (CDA-93X) for Mossberg 930/935 series shotguns is designed to properly bias factory polymer stock fitment for left/right handed shooters. The CDA also allows for an additional rise/drop in the stock with modified use of the factory receiver shims included with your 930/935. Our companion Recoil Pad Spacer (RPS-93X) allows for a longer Length of Pull than the factory stock, improves balance of the gun and allows simple installation of additional weight.

Natural Habitat Application Features Color Price Status ORDER
Cast/Drop Kit



Complete Set
(CDA, Nut &
Drop Shim Set)

(Left/Right Handed)

Storm Gray

Shims are
Pitch Black






Adds to LOP
(0.375" per plate)

Adds Balance
(3.5 Oz per plate)

Pitch Black


Having YOUR shotgun fit YOUR body is critical to maintaining proper sight picture and repeatability in quickly mounting the gun. Adjusting your position and craning your head on the clock doesn't help your order in the prize table line.

Mossberg Factory Shim on Receiver Mossberg Factory Shims Mossberg Factory Plate in Stock

Mossberg 930/935 Series shotguns with factory polymer stocks include a set of receiver shims and stock plates that allow for up to .375" of Rise adjustment and .250" of Drop adjustment. While this is a good start for many to fit the gun to their body, it often isn't quite enough and ignores critical cast adjustment. After analyzing the space left on the table (or inside the stock) for additional adjustment, we designed a system to take full advantage of every last bit we could find without requiring modification to the factory stock. As the CDA can be slid up or down inside the polymer stock, the full amount of rise/drop will depend on the tolerances of your gun's polymer stock internals and your tolerance for making minor internal modifications to your polymer stock.

CDA Plate Installed in Stock

Primarily, the CDA allows easy adjustment of the factory polymer stock for CAST, which is the often overlooked left/right placement of the stock in relation to the centerline of the barrel. The Mossberg 930/935 has a fairly neutral stock, which can be improved for fitment of both left and right-handed shooters (with our CDA) by installing the core parts (Adapter & Receiver Shim) oriented in either left or right handed configuration. When viewed from the rear, lefties should start with the small holes of each part on the left, while righties should orient them to the right. These components alone create .125" of cast on or off, depending on the installation. Factory Rise/Drop shims can be combined with either Cast setting of the CDA.

Orientation for Left/Right Handed Use

The DROP feature of the CDA allows additional (over factory) Drop/Rise when combined with modified factory stock shims and retention plates. In most cases, the CDA can increase the amount of drop possible when used with our optional Alloy Drop Shims or allow stacking of the factory .375" and .125" Rise Shims. If you will be utilizing any rise or drop with your stock you will need our Short Stock Nut Spacer in order to have adequate threads for tightening your stock. This is also critical to have if you are using a thick sling adapter between your receiver and stock, with or without the CDA kit.

Stock/Receiver Sling Mount

Combining factory Rise shims at the stock/receiver joint (such as a .375" & .125") would allow additional rise when the CDA's adapter plate is slid into position to match and locked in with the included set screws. This is handy for a 930 with an optic on it and/or tall sights like an SPX. The length of the alignment pin on the back of your receiver and thickness of your factory shims will also determine the amount of rise or drop that is practical with your gun. Consideration must also be made for how 'true' the recoil tube is machined into your receiver. Our alloy Drop Shims are thinner (while still at the correct angle), allowing you to take advantage of the full drop capabilities of your factory stock and still maintain alignment with the factory pin. Full drop may also require minor modification to the polymer stock's recoil tube channel.

It is important to note that not all Cast, Drop, Rise and or sling mounting plate combinations are possible with the amount of 'play' in the factory tolerances.

Shim Stack - No Alignment Pin

For instance, while stacking the cast shim, an OEM .250" drop and an OEM .125" rise would in theory yield a .125" drop with cast adjustment, the stack of polymer shims would be too thick to allow the receiver's pin to engage the stock. This shim stack would also increase the shotgun's Length of Pull.

Recoil Pad Spacer - Marine Blue

If you are one of those that would benefit from a longer Length of Pull, our Recoil Pad Spacer (RPS) offers a number of features. Each of these 6061 alloy spacers adds 0.375" to your LOP and 3.5 oz of weight to better balance your shotgun. Adding to your Length of Pull is another way to get additional Drop, as this is a natural effect of doing so.

Complete RPS Kit RPS Installed - Marine Blue RPS w/ Optional Weights

Up to 3 RPS plates can be stacked and secured with the included bolt and nylon locknut. Alternately, the bolt and nut can be used to secure a stack of 3/4" fender washers for additional weight. More than one RPS will require that longer recoil pad screws be sourced from a local hardware store.

The complete process for configuring these components will be detailed soon over a series of 930/935 fitment videos on our YouTube channel.

The CDA plate, RPS plate and short stock nut spacer are machined entirely from 6061 T6 aluminum. Shims are either ECO-ABS or 6061 T6, depending on the kit and application.

Watch Part I in our YouTube series on fitting your 930/935, featuring our Cast/Drop Adapter!

Watch Part II in our YouTube series on fitting your 930/935, featuring our new Recoil Pad Spacer!

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.