Bought a Scattergun Technologies 2 rnd extension for my 870 and found out the magazine tube is staked or dimpled about an inch from the end. These dimples in the metal tube wont allow the follower or shells to go past them, rendering the extension useless. Any ideas?

Do a search on this forum, there's a BUNCH of info on this.

Basically, you have to remove the dimples by grinding them off or by drilling them out with a 1/4" drill.

Whichever method you use, you have to make SURE the inside is smooth, and no trace of the dimples are left.
Almost smooth WON'T do it.

Also, once the dimples are gone, you can't go back to a standard non-extension magazine, at least not easily.

Thanks.

If you use a rat tail file you won't have holes in your extension from drilling, IMO.

Once you remove the dimples, there's nothing to lock the plastic magazine cap retainer plug in place.

Without the plastic retainer, just screw the cap on the gun, and recoil will usually loosen it quickly since there's nothing to lock it in place.
Also, without the plastic plug, there's nothing holding the mag spring in the tube.
Unscrew the cap, and you get a face full of spring.

In order to convert back to a standard magazine, you need to buy an old style mag cap retainer spring and plunger.  Install it into the barrel support ring, and buy a old style magazine cap and the old style spring cup mag spring retainer.

If you check around, you can often find like new old style mag caps and spring cups at gun shops, or even with other shooters.

The problem is the retainer spring and plunger.  These need to be ordered, AND you have to buy the special punch that's used to stake it in place in the barrel ring.

Quoted: Some people had 870s before this nonsense.

My Rem 870 Wingmaster doesn't have the little dimples, but my 11/87 does. Personally, I don't know why the good folks at Remington put those in dimples in for.

Thanks to all. Drilled 'em out, deburred inside with dremel, then hit with 1000 grit sandpaper. Works perfect.