Shotguns are powerful and versatile weapons but they have very limited magazine capacity. That is why this is one of the first things for a shotgun owner to improve when he starts building his tactical / home defense Remington 870 shotgun.

A lot of Remington 870 owners want to install a magazine extension on their shotguns. But there are dimples in magazine tube which must be removed first. And all of us are afraid to break our favorite shotgun during this process.

What is the purpose of the dimples inside the Remington 870 magazine tube?

I have received answer about dimples directly from the Remington:
“The dimples in the magazine tube is to keep the new style retainer in place. If the
dimples are removed, the retainer would not stay in place. We do not recommend these
dimples to be removed. This style was introduced in the late 80’s.”

But if you want to install magazine extension you still need to drill them out first.

Dimples were not in magazine tube forever, Remington started to punch them into magazine since 1990 or little later. There are no dimples in Police version of Remington 870 (standard Remington 870 Express magazine capaciy is 4+1, or the one with factory magazine extension is 6+1, but it has dimples too)

Some owners say that drilling them out leads to rusting of your magazine tube so you may find it useful to cold blue it.