A Little More Information About Dimples in Magzine Tube

Dimples were not in magazine tube forever, Remington started to punch them into magazine since 1990 or little later. Their purpose is to stop owner from using a magazine extensions. 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.

UPDATE: Dimples in Magazine Tube of Remington 870