Pennsylvania Firearm Owners Association
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  1. #1
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    Default Removing Rem 870 12ga mag tube dimples to install extension...

    in the future, to avoid either "pricey tools" or a grinding mess... do this... those familiar with using a hammer and dolly for metal auto-body work will get this...

    on mine, a Craftsman 3/8" drive 11/16 deep socket nearly perfectly matches the Inner Diameter of the rem 870 12ga mag tube, the socket is only slightly smaller than the ID of the tube, and will just barely slid in the mag tube.

    clarification due to posts made below: THINK PEOPLE!! The socket has to fit inside the mag tube in the undimpled portion FIRST, you only have to use the rubber hammer to knock the socket past the dimples to press them out. If you have to use the hammer to actually get the socket IN the tube at all in the first place, STOP!!!! you are using the WRONG diameter socket (this is common sense here folks).

    remove the magazine tube cap, spring, follower, barrel, action bars and fore-end.

    Oil the socket, and using a rubber hammer, drive this OILED socket into the end of the mag tube to knock out the dimples.
    when the socket has pushed the mag tube dimples out, complete the flattening of them with a smooth headed hammer, using a lot of light taps instead of hard ones, until the dimple is fully smooth on the inside.

    the socket works as the anvil for the hammer to pound the dimple out.

    No muss, no fuss.

    you may require a ratchet handle to rotate the socket free when finished.

    use as much as you like

    you can see the external remainder of the dimple, the interior is smooth as the rest of the tube.

    Last edited by JayBell; August 22nd, 2012 at 03:45 PM. Reason: edited to clarify what I thought was obvious
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  2. #2
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    Aug 2011
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    Coral Springs, Florida
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    Default Re: Removing Rem 870 12ga mag tube dimples to install extension...

    Thanks. I have been seeing this technique used a lot, even on youtube. I want to do this to my brand new 870 express. I converted it to a Remington 18" barrel but I don't know which 2 shot mag extension tube to use.

  3. #3
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    Default Re: Removing Rem 870 12ga mag tube dimples to install extension...

    I started trying to do this. Followed the directions, smacking the 11/16ths in with a light rubber mallet into the mag tube. I didn't get too far before I started thinking the first thread or 2 on the end of the receiver mag were getting too big to thread a coupler to. So I stopped. Sure enough, too big to thread the coupler for the mag extension on. Worse yet, too big to put the forend tube over.

    Now I'm thinking I either have to cut it off below the threads and dimples, and have it rethreaded somewhere, or just buy a whole new receiver. I'm not happy with either option. Any other suggestions? Lots of room in the tolerance specs? My 870 takes the older slide, maybe it's changed the tube diameter by a hair too?

    Unless I missed something, this method above isn't one I'd recommend. I'm about to just buy the police 870 receiver, if I can find one, and be done with these f-king dimples.
    Last edited by richrock; September 9th, 2011 at 11:50 PM. Reason: new thought

  4. #4
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    Thumbs up Re: Removing Rem 870 12ga mag tube dimples to install extension...

    I am sooo glad that I did not follow this method to modify my Remington. I just completed the mod earlier today...yes, I went out a purchased an average Dremel, drilled out the dimples and smoothed out the inner tube. The entire process took all but 20 minutes. Also, I trimmed the tube spring by approximately 7-8 loops and now the magazine slides 8 cartridges with grace...of course, I field stripped and cleaned the ENTIRE shot gun before I began the modification. NEVER bang on the front of a gun with ANYTHING...PERIOD!

  5. #5
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    Default Re: Removing Rem 870 12ga mag tube dimples to install extension...

    apparently, those who failed using this method used a socket with too large an outer diameter.

    the section where I said "this nearly perfectly matches the ID of the rem 870 12ga mag tube." clarification: the socket has to fit inside the mag tube, you only have to use the rubber hammer to knock the dimples themselves out, if you have to use the hammer to actually get the socket IN the tube at all, you are using the WRONG diameter socket.

    good luck folks, and THINK first before just whacking away at things... I have edited the procedure post to point this out....
    Last edited by JayBell; July 13th, 2012 at 03:55 PM.
    "Oderint Dum Metuant" - BMFH

    "Tact is for people not witty enough to use sarcasm"

    Note: any whingeing crazy that hits my PM inbox will be deleted without reply

  6. #6
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    Feb 2011
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    Default Re: Removing Rem 870 12ga mag tube dimples to install extension...

    Hope I'm not stepping on any toes, just wanted to share my experience with doing this.

    I have a Hawk 982 shotgun, which is for all intents and purposes an 870. The mag tube is a little longer, but from all the images I've looked at the dimples are done the same way.

    After dissembling the gun, I selected a deep socket that just fit inside the undimpled portion of the mag tube without too much drag. All sockets vary in wall thickness, so there is no one correct size. I then lubricated the socket with clean motor oil, as well as the inside of the mag tube.

    Using a 3" extension, I drove the socket through the dimpled section using light taps with a plastic hammer. Once it was inserted sufficiently, I attached a ratchet to the extension and turned the socket until it came free again.

    At this point, the socket still slid freely into the undimpled section, but still had enough drag on the dimples to require a solid push to get it past.

    I used one additional step to make sure the remaining dimple impressions did not interfere with feeding. I took a 1/2" diameter wood dowel, and cut a 1" long slit down the middle. Inserting some 600 grit emery cloth into the slit, and fixing the dowel in a power drill, I spun it inside the tube, working back and forth over the dimpled area. It only took a few seconds, and the socket would move freely through the whole length of the mag tube.

    I then cleaned the tube and receiver, applied a little cold blue to the section I used emery cloth on, and reassembled. Zero feeding issues using a 2 round extension. If you look, you can still see the dimples on the outside of the mag tube, but the inside is uniform.

    Total time minus disassembly/reassembly was less than half an hour.

  7. #7
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    age: 57 Dillsburg, Pennsylvania
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    Default Re: Removing Rem 870 12ga mag tube dimples to install extension...

    Seems to me that if one measured and made a sturdy sleeve that was a slip fit on the OD of the mag tube, and located it right over top the area of the dimples to support the tube and prevent distortion, one could drive a mandrel (socket?) the exact size of the mag tube ID right through without distrubing the thread or tube dimention at all, pressing only the dimples flush with the mag tube ID. One might have to have some access to a lathe and a pair of calipers to make said collar, but it ain't rocket surgery. I think I just gave myself an ideer!

    Note to self: tomorrow, make heavy OD collar and ID tapered mandrel. Maybe I should start a tube extension installation kit business?

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