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OR3GUN Competition Forearm Retainer (Alloy) Fitment Guide

Discussion in 'OR3GUN' started by OR3GUN, Feb 23, 2015.

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What version is your 930 receiver's 'roll mark'?

  1. Eagle Pass (No Mossberg Graphic)

    0 vote(s)
    0.0%
  2. North Haven (No Mossberg Graphic)

    18.2%
  3. North Haven (Mossberg Graphic)

    63.6%
  4. Other

    18.2%
  1. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    195
    So, which receiver version do YOU have? (Poll available above...)

    The OR3GUN Alloy CFR was designed around as many receivers as we could get our hands on. In order for the part to fit each of them as tightly as possible, we had to design it around the smallest. The smallest and easiest to fit receivers appear to be the Eagle Pass factory guns from a few years ago.


    [​IMG]

    The Eagle Pass guns with the above marking (or what's left of it) should accept the Alloy CFR with zero to minimal modification. All of the Eagle Pass guns we tested with the above version of the roll mark accepted the part without issue.


    [​IMG]

    The North Haven guns with the above marking (or what's left of it) should also accept the Alloy CFR with zero to minimal modification. Only one of the North Haven guns with the above version of the roll mark required any fitting. The only fitting required was a couple of passes at the corners of the CFR's receiver overhang with a flat file as shown below:

    [​IMG]

    This simple modification was all that was necessary to fit the Alloy CFR to the North Haven guns we have run across with the traditional 'Mossberg 930' embossing on the side of the gun, under the loading port, directly behind the bolt release.

    [​IMG]

    While the above receiver style is what the bulk of Mossberg's 930 line looks like, the JM-Pro appears to be exclusively made from the North Haven style of receiver as shown below.

    [​IMG]

    The newer North Haven guns with the above marking (or what's left of it) required the most fitting in our testing. Every one of these we have run across has been a JM Pro, with the laser etched receiver rather than the embossed 'Mossberg 930' labeling on the side. The following is what the initial fit test of the Alloy CFR looks like on one of these guns:

    [​IMG]

    As you can see, we are not quite there on this gun. While a few simple swipes of the flat file will fit the Alloy CFR to the receiver on other 930s, the factory changes to the JM Pro (and possibly other recent) North Haven receivers require that a small portion of the end of the inner edges of the Alloy CFR's receiver overlap be taken off with a dremel or similar tool:

    [​IMG]

    The CFR should FIRST be fitted to the receiver before attempting to fit it to the forearm. Once the CFR to receiver fitment is complete and your forearm modifications (if any are done) you can proceed with fitting the CFR to the forearm itself.

    [​IMG]

    If you will not be modifying your forearm beyond that of a typical JM Pro, you will need to round the hard corners of the CFR in order to draw the forearm closest to the receiver when installed. This will allow the tightest overall fit for weak hand and/or some load two loading methods. This rounding (as shown on the left CFR) is easily done by dragging the corners over a sharp flat file.

    [​IMG]

    The Mossberg 930's receiver is fairly squared off, as are both the OEM and OR3GUN Forearm Retainers. The inside of the Mossberg 930 Forearm is quite rounded, presenting us with an opportunity to make them match within the confines of the CFR. There is a critical element to doing this while maintaining proper cycling of the gas system. The pusher assembly must have proper clearance. You can check the amount of room you have to work with by placing the fitted CFR on your receiver's magazine tube and installing the pusher assembly WITHOUT the spring. This will show you the absolute limits of the modifications that can be done to improve your loading port and forearm fitment. This is a judgement call that will need to be made as you profile the forearm and Alloy CFR. That said, DO NOT modify the peak at the apex of the part, as this must be maintained for absolute minimum clearance standards.

    [​IMG]

    As you can see from the image below, completing the rounding process to draw the forearm closer the the receiver is done with the removed forearm as your template. It is absolutely CRITICAL for proper cycling of the gas system that you not modify the slight 'peak' visible at the bottom of the unmodified part.

    [​IMG]

    It is best to modify the profile of the Alloy CFR to blend with the bottom of the forearm BEFORE adjusting the tangs at the top of the Alloy CFR for fitment into the retention rails. The Mossberg 930's Forearm, regardless of your loading modifications will rely on this geometric relationship as visible above. If there is a gap between the top of the CFR's retention tangs and the forearm's retention rails when disassembled from the gun, it will result in play once installed. At the same time, if it is nearly impossible to force the CFR into the loose forearm, you run the risk of forcing the forearm on the gun for assembly and potentially drawing it down into the pusher assembly. Simply put, don't mess up the cycling of your gun in the pursuit of an additional 0.010" worth of forearm reduction.

    [​IMG]

    For extreme levels of modification you may need to take a look at your OEM Pusher Assembly to ensure that there are no burrs or molding marks that will drag against your forearm innards while cycling.

    [​IMG]

    Once your Alloy CFR is properly fitted, installed and tested you can taper it to blend from receiver to installed forearm. Hopefully, the above fitment guide should be all a qualified gunsmith needs to properly incorporate the Alloy CFR into any 930 currently on the market. Please let us know if you run across one that differs from those identified in this fitment guide.

    Hopefully this helps 930 owners see what they are getting into with the Competition Forearm Retainer. We hope you will also take our poll and help us determine what receiver versions are most common and help us find any others that may be out there. Thanks!

    [​IMG]

    - William

    http://www.OR3GUN.com
    Waitster and DHonovich like this.
  2. DHonovich

    DHonovich Founder Staff Member Administrator Sponsor "Philanthropist"

    Messages:
    6,921
    It is great seeing products like this hit the market for our beloved Mossberg 930. Mine is a logo but it does not say where its made in that area you have pictured.
  3. DHonovich

    DHonovich Founder Staff Member Administrator Sponsor "Philanthropist"

    Messages:
    6,921
    [​IMG][​IMG]


    Sent from my iPhone using Tapatalk
  4. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

    Messages:
    21,112
    ^ That's what happens when you file off all your serial numbers and such... ;)
    Waitster and DHonovich like this.
  5. Pawpaw

    Pawpaw .30-06 Supporter

    Messages:
    1,254
    My SPX has no stamp either. It looks just like yours.

  6. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

    Messages:
    21,112
    My 930 Tactical (2011) has no roll marks, but my JM Pro (2013) does feature the brand graphic and North Haven roll mark...

    [​IMG]
  7. MikeD

    MikeD I'm Your Huckleberry Staff Member Global Moderator "Philanthropist"

    Messages:
    11,476
    I'll have to check mine tonight and post up what I see.
  8. krbrand

    krbrand Copper BB

    Messages:
    8
    Box stock (2012) 930 SPX Blackwater IMG_0006.JPG
  9. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    195
    Interesting. It had been assumed that the guns without roll marks ahead of the loading port were North Haven guns manufactured before Mossberg had opened the Eagle Pass factory. That would have made them 90s or older. They must have continued to leave their North Haven guns unmarked for quite some time. Sounds like it's time to see how a CFR fits a blind marked 930.
  10. MikeD

    MikeD I'm Your Huckleberry Staff Member Global Moderator "Philanthropist"

    Messages:
    11,476
    My 930 Waterfowl model has no markings:
    930Feed_001.jpg 930Feed_002.jpg
  11. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    195
    We've got an Alloy CFR on the way to a non-marked 930 to see what level of fitting will be required. We will update the guide when we get feedback.

    - William
    Pawpaw and DHonovich like this.
  12. Pawpaw

    Pawpaw .30-06 Supporter

    Messages:
    1,254
    I ordered one too and it's supposed to be here Monday. If there's any way I can help, let me know.
  13. DHonovich

    DHonovich Founder Staff Member Administrator Sponsor "Philanthropist"

    Messages:
    6,921
    [​IMG][​IMG][​IMG][​IMG]



    Sent from my iPhone using Tapatalk
  14. Pawpaw

    Pawpaw .30-06 Supporter

    Messages:
    1,254
    Mine arrived today and the fit looks exactly like DHonovich's pictures. So near, and yet so far.
    DHonovich likes this.
  15. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    195
    So, from the feedback so far, it looks like the Eagle Pass and North Haven guns (marked in the same style) are the same and are essentially drop-in at the receiver level.

    Those that are unmarked and those that are otherwise marked as North Haven will indeed require the expected fitting of the JM Pro models under the corners of the receiver overlap.

    - William
  16. MikeT

    MikeT .270 WIN

    Messages:
    395
    IMAG1560.jpg IMAG1561.jpg
    Here is what my 930SPX looks like. What work would be required for this model?
  17. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

    Messages:
    12,497
    Link not working Mike.
  18. MikeT

    MikeT .270 WIN

    Messages:
    395
    Try again... I was doing something to cause the first image to be show twice instead of once like I wanted... GGRRRRRrrrrr.
  19. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

    Messages:
    12,497
  20. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    195
    From what we've seen of that style of North Haven receiver, you would need minor material removal from the edges of the inside of the flange that overlaps the receiver.

    A dremel with a straight cutter bit as shown above in the original post works great for this.

    - William

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