What Size Forend Tube Do I Need?

Discussion in 'Mossberg 500 Pump Action' started by blacksmith, Dec 15, 2014.

  1. blacksmith

    blacksmith .223

    Messages:
    309
    Just Kidding

    In this post we'll discuss the Mossberg forend tube. There are different names for the part - action tube, pump, slide. Unfortunately there are different styles of this part which causes much confusion. We'll go over the different versions and at the end post the famous chart.

    There are three distinct forend tubes. Any tube will fit any gun within its respective gauge. We will state what each gun typically comes with, but in reality this is subject to change.

    7 5/8 'Long' forend tube. This is the original tube. Early ones were rattle traps, dimples and springs were added later. Most factory & aftermarket forends fit this length. Typically found on early guns and new security models. Total weight with forend is 11.5 ounces.

    6 3/4 'Short' forend tube. These originally came out on sporting models. The 14 SBS requires this forend due to its short magazine tube. Also weighs 11.5 ounces.

    One-piece Polymer Forend. These have steel action bars pinned to a solid polymer forend. There are two types. The ribbed version is sturdy, lightweight forend that will not scratch the magazine tube like the steel forends. It is a good choice. The checkered forend is well known to break and not recommended. Weigh 7.5 ounces.

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    Last edited by a moderator: Jan 12, 2015
    RichardL, Rossignol, Bobster and 3 others like this.
  2. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    Good info all in one spot.

    TY blacksmith.

    Merged this from forend thread,,,,


    Mossberg 500/835 acton slide tube changes

    Action Slide Tube Assemblies Lengths: There are two different action slide tubes (forend tube) used on the 500 (all gauges) and 835 pump action shotguns. It is imperative to know the length of the original when replacing the action slide tube or the forearm as individual components.

    Prior to 1973 all action slide tube assemblies utilized tubes with a length of 7-¾". In 1993, running production changes commenced to change over to a tube with a length of 6-¾" in all gauges. The change will typically found in the Model 500's with serial number prefix K3 and Model 835's with serial number prefix UM or higher (K4, K5; UN, UO). There is an exception: All Special Purpose, Persuader and Cruiser produced to date still use the 7-¾" action slide tube assembly.

    The current production 6-¾" action slide tube assembly, with appropriate forearm, may be used on models previously using the 7-¾" action slide tube. In some instances modifications will be required as noted below.

    Single Arm Action Slide Tube Assemblies: Early production Model 500 shotguns utilize an action slide tube assy. (forend tube assembly.) with a tube length of 7-¾" and a single action arm. This tube assembly is obsolete. A twin bar action slide assembly with a tube of the appropriate length may be used as a replacement for the obsolete single arm action slide assembly. If both the action slide tube assembly and the forearm are being replaced, they may be replaced with either 7-¾" or 6-¾" action tube assemblies and matching forearms as available.

    G Serial Number Prefix: All Model 500 shotguns with a G serial number prefix utilize a specific magazine tube with a ring system around the external diameter of the magazine tube. This utilizes a specific action slide tube assembly. Both the magazine tube and action slide tube assembly for this variation are obsolete. If replacement is required both the magazine tube and action slide tube assembly will require replacement. The 7-¾" or the 6-¾" assemblies and magazines tubes, current at the date of this publication may be used as replacements. Insure that the length of the tube matches the original forearm or replace the tube and forearm with matching units.
    Last edited: Jan 12, 2015
    RichardL and Rossignol like this.
  3. Bobster

    Bobster .308 Supporter

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    1,305
    +1 on this! Great info post! :)
  4. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

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    21,056
    Deserved a sticky, so it's now stuck...
    old mossy likes this.
  5. kennungesser

    kennungesser .22LR

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    15
    I have a noob question. Flame on if you must. I just installed the Barska forend, and the original forend was the polymer one-piece. I did get OEM off without damage, so I can reuse if needed. My question is how important is the forend nut? There is absolutely NO way on Gods green earth I could reuse it. And this sucker is TIGHT without it. 12 gauge tight I don't know, but the threads are right up to the end, and will go no farther into the Barska. I resembled and ran some shells through it (though have not shot yet), and all is working as it should. I would like to take this out to my in laws this weekend and do some shooting and sighting, but I am worried about not having that nut on there. What do you guys think? Can up load pics tomorrow if needed. Thanks for any help,
    Ken
  6. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    12,184
    Welcome to the forum from NY.

    Sounds like you have a longer (7 3/4") forend on a shorter action slide.

    ,,,,,and don't ever worry about flaming here.
  7. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

    Messages:
    21,056
    Don't worry, there's no flaming here.

    Is your Barska forend the aluminum tri-rail? If so, it's the old UTG unit. I have installed two of them on my shotguns and they are designed to work with the longer 7-3/4" action tube and the short forend nut. Like @old mossy said, you likely have the short 6-1/2" action tube and need to order the longer adapter nut. It's a relatively inexpensive part. Post up pics when you get a chance and we should be able to tell for sure. I would not be comfortable shooting without a forend nut in place. While it may feel extremely tight by the hand, never underestimate what can happen under the force and vibration of recoil...
  8. kennungesser

    kennungesser .22LR

    Messages:
    15
    Yes it is the aluminum tri-rail. But there is really no room for the nut to spin on even if it were long enough. The threads touch the "end" of the tri-rail. I haven't forced on so there is not damage to the threads. I was TEMPTED to get the 'ol Dremel tool out and cut...but that has rarely worked out well in the past, no matter how fun it is to try to find an excuse to use it. But it looks like I could Just shave JUST enough off to get the nut to screw on.
  9. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

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    21,056
    Post up some pics before you fire up the power tools...
    old mossy likes this.
  10. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    12,184
    Take it off the gun and measure it and the other forend. Measure the inside from shoulder to shoulder.
  11. kennungesser

    kennungesser .22LR

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    15
    Here are some quick cell phone pics.
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  12. kennungesser

    kennungesser .22LR

    Messages:
    15
    Thanks for looking guys. I can stay much longer. Gotta be at work at 6:00 for a 12 hour day. Happy new year, lol. Oh well at my age, the partying is pretty much over, lol. All I want now are 2 palm trees, a beach and some rum-n-coke.
  13. LAZY EYED SNIPER

    LAZY EYED SNIPER Overwatch Staff Member Administrator Supporter "Philanthropist"

    Messages:
    21,056
    Took mine apart for a reference...

    [​IMG]

    It is a REALLY tight fit getting the nut onto the threads, but I've made it work on two different set-ups...
  14. kennungesser

    kennungesser .22LR

    Messages:
    15
    I CAN'T stay much longer...
  15. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    12,184
    Looks like the wrong size forend.

    You are trying to put a 7 3/4" forend on a 6 3/4 action slide.

    forend chart.jpg
  16. kennungesser

    kennungesser .22LR

    Messages:
    15
    The shoulder on the nut is preventing it from reaching the threads..I may be able to push the tube in a little bit farther.
  17. old mossy

    old mossy Global Moderator Staff Member Global Moderator Forum Moderator

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    12,184
    From those pics it looks like almost 1/2" just to start the threads.
  18. kennungesser

    kennungesser .22LR

    Messages:
    15
    So I may be able to use the Hogue nut? Is this something a gun smith would carry, or would it have to be ordered? I don't know how common a part like this would be.
  19. kennungesser

    kennungesser .22LR

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    15
    Yes, old mossy..dang good eye. Almost exactly 1/2 inch and I would have it.
  20. kennungesser

    kennungesser .22LR

    Messages:
    15
    So...no nut, no shoot? What could happen? I am only shooting bird shot to get a pattern down.

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