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940 piston to 930?

Discussion in 'Mossberg 930 Autoloader' started by Djhomie, Apr 22, 2020.

  1. Djhomie

    Djhomie Copper BB

    Messages:
    2
    Anyone tried already? 940 piston to 930 ? Since SBE precision doesnt have stock
    Yet, i just wanted to ask if someone tried already , thanx
  2. AngryWaffle

    AngryWaffle .22LR Supporter Elite Member

    Messages:
    15
    I've been thinking the same thing. I'd rather support SBE Precision. When I asked, I got a reply back saying things are crazy and uncertain right now. I will wait to see if I can hopefully purchase from them.
  3. Djhomie

    Djhomie Copper BB

    Messages:
    2
    I email them SBE when they will have stock , yet no apparent date yet but they said in future, and i also ask mossberg if i can purchase a piston from 940 they said check back in the end of the year might start that month and they knew my idea of using it on 930 they told me fitting it on 930 will not work, they are unsure, for me i believe its same . Because the 940 been out now and the replacement parts still not, they know sales of 940 will be slow if gas piston is fitted and work properly what u guys think??
  4. Rob72

    Rob72 .410

    Messages:
    80
    It pretty well has to, otherwise, Mossberg would have had to do some retooling, and they aren't exactly known for "proprietary" models.
  5. OR3GUN

    OR3GUN Sponsor Sponsor

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    218
    The 940 piston is a bit shorter (~ 1/8") than the 930s. It also still incorporates in internal ring, unlike the SBE piston. While the receiver and magazine tube is essentially the same on the 940, none of the internals forward of it are. That said, you CAN place the entire 930 front end (receiver forward) on the 940 and have a functional shotgun. (You can't quite as easily go the other direction.) We've had two 940s in the shop for a while now and there are some OR3GUN parts pending for it. We plan to post a thread of comparison pictures of the major 930 & 940 components, but may wait until there is a 940 section and we have answers to some of the questions.

    The most obvious potential issue with running a 940 piston in a 930 is the shorter piston length would allow the external gas ring to partially leave the cylinder. Small, intentional crescent cut-outs at the end of the cylinder on the 940 would indicate Mossberg found a partial vent of the gasses to be beneficial in keeping the system cleaner. That would be different than letting the ring exit the cylinder completely, which they could have done without changing the cylinder (and therefore, complete barrel assemblies) for the 940. The guess at this point is that they may expect that rings wouldn't wear well being violently re-seated into the cylinder with every shot.

    There is more than a bit of head scratching to be had with some of the design decisions made on the 940.

    William

    http://www.OR3GUN.com
  6. Rob72

    Rob72 .410

    Messages:
    80
    Thanks, William,

    What about the pusher? Can that be run in the 930, with the 930/SBE piston? Is it a more robust design?

    Inquiring minds...
  7. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    218
    C3964760-0D70-452B-B495-0879BC286AB8.jpeg The pusher assembly is narrower and longer, so it can fit under the new forearm profile.

    It could be used with the 930 in conjunction with a shorter spacer tube. The spacer tube can't be the same length as the 940 though, due to the piston length.
  8. Joker18

    Joker18 .22LR

    Messages:
    18
    Good info OR3GUN! I have so much OR3GUN and SBE stuff in and on my 930, I would put it up against a 940 any day of the week. I am undecided as to buying a Choate buttstock, because I like having my hand situated close to the safety. I wish Magpul would design a buttstock for the 930 like the one I have for my Model 500. I have emailed them and I was informed they have no future plans to do so. The Magpul buttstock on the Mossberg 500 is a perfect compromise between the standard shotgun buttstock and a pistol grip buttstock.
  9. steven berson

    steven berson Sponsor Sponsor

    Messages:
    29

    I have started a new batch of pistons, and am working on them now. I am hoping to have complete parts in a couple weeks. Thank you guys for all your support and patience.
  10. steven berson

    steven berson Sponsor Sponsor

    Messages:
    29
    PTAGP100 likes this.
  11. Rob72

    Rob72 .410

    Messages:
    80
    William,

    Because I'm a tinkerer...:

    In looking at the 940 pusher, does it appear to be more robust, e.g., there is a moulding band around the base of the pusher rods, is there possibly a metal ring welded to the rods, etc., etc.? Does there appear to be a functional reason not to take a chopsaw to the spacer end, to bring it down to 930 OAL?

    Yes, I'm probably going to obtain my own to play with...eventually...:popcorn:
  12. OR3GUN

    OR3GUN Sponsor Sponsor

    Messages:
    218
    We have yet another 940 JM PRO awaiting the overwhelmed Oregon background check process (of over 2 weeks, where it was once 20 minutes). This 940 will be 'sacrificial' in nature and donating a great many of its organs to science.

    If we can get our hands on 940 pushers in bulk we will have a solution that allows the SBE piston and our existing spacer to function in the 940 dimensions. We have another 940 that is running the SBE piston and a shorter prototype of our spacer with the factory 940 pusher. The idea is to support every level of 930 to 940 conversion with as many existing OR3GUN and SBE 930 parts that you may already have for the conversion to the slimmer forearm and any required internals.

    It is an interesting time to try to accomplish R&D, but since most 3-Gun around here has been cancelled, we at least have plenty of ammo to feed the prototypes in testing. We have our 940 page up with the first production run of recoil system parts. We also lay out some of the changes and detail what we are tackling first in prototyping. With a sharp eye over the next few days you will see other things we are working on.

    http://www.or3gun.com/OR3GUN/about_or3gun_940_parts.htm

    -William

    http://www.OR3GUN.com

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