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Thread: Threading for a Choke

  1. #1
    Join Date
    Jun 2001
    Location
    McKinney, Texas
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    1,917

    Default Threading for a Choke

    I have a Mossberg 930 and wish to prepare a barrel to accept interchangeable choke tubes. Being completely new to gunsmithing, I am curious - what all is involved?

    Thanks.

  2. #2
    Join Date
    Feb 2011
    Posts
    152

    Default

    You can buy a reamer and tap from Brownells.

  3. #3
    Join Date
    Aug 2011
    Posts
    3

    Default

    Pacific Tool and Gauge and Manson Reamers make reamers and taps for modifying your shotgun.

    The Rem-Choke reamer and tap will install threads that will accept Rem-Choke and Remington factory tubes. For a 12 gauge, that means a choke with an outside diameter of .814" and 32 TPI.

    The Win-Choke reamer will also cut to .814” and with a 32 TPI which allows you to use original equipment tubes from Win-Choke, Mossberg Accu-Choke, Weatherby, Browning Invector. (Note that although the thread pitch is the same, the shape is different between the Remington and the Winchester reamers)

    Then there is a Tru-Choke reamer that will cut for .795” diameter choke tubes at 44 TPI and a Tru-Choke Thin Wall reamer that cuts .775” at 44 TPI for thin barrels. The Tru-Choke will accept Tru-Choke choke tubes, while the thin wall will only accept the Tru-Choke Thin Wall Tubes.

    The reamers use a pilot bushing to center the reamer in the bore. The pilots come in various sizes to fit your bore.

    It is recommended to use a lathe for the best possible results, although the reaming an tapping can be done by hand.

    It is also recommended that you use an expanding reamer to remove the choke (the fixed one) prior to reaming the barrel.


    Screw in choke installation requirements:

    Before machining a barrel to accept screw-in-chokes, you must measure the outside diameter of the barrel to determine if there will be sufficient wall thickness after reaming.

    Measure the O.D. of the barrel and then measure the O.D. of the tap. Subtract the O.D of the barrel from the tap and then divide by 2. This will give you the wall thickness after reaming.
    For example; .850” barrel O.D. minus .814” tap O.D. equals .036”… Divide that by 2 and you get .018” wall thickness.

    It is not recommended to perform this procedure where the wall thickness will result in less than .015”. Also, for a 12GA, you shouldn’t proceed in installing these chokes if the Inside Diameter exceeds .735” (.728” for thin wall chokes) .Exceeding these dimensions WILL cause damage to the chokes and a GREAT POSSIBILITY of barrel BLOWOUT. After installation, make sure the tube does not protrude into the bore. Back-bored or jug-choked barrels are usually not suitable for this installation.

    Note: These reamers and taps are not cheap alought it may be possible to rent one. (Yeah, you can, try here: http://www.4-dproducts.com/display.php?group=Shotgun )

    Brownells:
    http://www.brownells.com/.aspx/cid=0...=choke_reaming

    MidwayUSA:
    http://www.midwayusa.com/Find?status...temsPerPage=20

    I hope this helps.
    Last edited by John 242; 10-23-2011 at 04:04 PM.

  4. #4
    Join Date
    Jun 2001
    Location
    McKinney, Texas
    Posts
    1,917

    Default

    Thanks a bunch!
    I didn't realize that a reamer and tap were requisite. Since I don't intend to do this regularly, it won't be worthwhile to buy the tooling.

    So, 2 new questions:
    1) Is anyone here interested in doing this job? (btw, the barrel OD is .910)
    2) Which choke should I thread for? It seems logical to go with the factory configuration. I intend to use ported chokes, which it looks like Mossberg offers in the PF line, and which will also apparently fit my model 88 back-up gun w/accu-choke. Will need a skeet-thru-full set of chokes.

    http://www.mossberg.com/cgi-bin/comm...tion&key=95500

    "Fits Mossberg Accu-Choke models, Maverick Accu-Choke Winchester 1300, Browning Invector models, Ithaca, New England Firearms Pardner, Stoeger Uplander/Condor models, H&R Excel (12 Ga. only)"

  5. #5
    Join Date
    Aug 2011
    Posts
    3

    Default

    Gun Broker has Mossberg 930 barrels for around $150.
    Might want to think hard about whether you want to modify your barrel or simply buy a new one.

    http://www.gunbroker.com/Auction/Vie...Item=255666833

  6. #6
    Join Date
    Dec 2007
    Location
    Montezuma, IA
    Posts
    966

    Default

    Good information from John 242. You might want to make up a plug gage to check your bore behind the existing fixed choke, of .7355". If the gage goes into the bore past the forcing cone, the bore is too large for standard chokes such as RemChoke or Win Choke. Any scrap material an inch long with about a ten inch handle on it will work, just don't force it!

    David
    David Kaiser
    Montezuma, IA

  7. #7
    gary350 Guest

    Default

    The barrel has a standard type thread that fits all the chokes. Best thing to do is take it to a gun smith with the correct tools. You won't be able to get the threads straight without the correct tools. The gun smith I know has a barrel lathe with 2 collets. One fits the tip end of the barrel and the other collet fits about half way up the barrel. With the stock removed the barrel rotates at about 20 RPMs for cutting the threads. He can cut the threads in 15 minutes and charge you less that it will cost you to do it yourself.

    I made my own choke once it took me about 4 hours to make something I could have bought for $15. I won't be doing that again. I ended up buying 2 partical choke sets on ebay to get a full set now I have 1 extra chokes I don't need but so what I still got a good deal. Can't sell chokes on ebay anymore or any type of gun parts either.
    Last edited by gary350; 10-25-2011 at 11:40 AM.

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