Removing Rem 870 12ga mag tube dimples to install extension...

[JayBell]

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.