If you owned a Remington 870 Express and tried to install an extended magazine, you probably figured out the hard way it wasn’t so easy. The magazine tubes on many 870 Express models have a pair of dimples that prevent the shells and follower from passing through. This interferes with installation of an extension. I most recently encountered the magazine dimples when I wanted to install a one-shot magazine extension on my TAC-14.
Remington uses two different magazine cap retention systems on the Model 870 shotgun. The traditional system uses a detent forward of the barrel lug that engages the magazine cap. With the introduction of the Express line of shotguns, Remington started using an internal ratchet system. A plastic plug known as a magazine spring retainer, ratchet style (I sometimes refer to it as a plug, see the image below) that engages the inside of the magazine cap. The retainer is held in place by two detents stamped into the magazine tube that prevent it from spinning inside the tube and unscrewing itself from the cap.
Note the teeth located inside the magazine cap on this system. This part is known as a “magazine cap, internal ratchet”.
Compare this to the standard magazine cap above. Note the dimples for the detent on the barrel lug to engage.
The magazine spring retainer and internal ratchet cap system are cheaper to manufacture and, as previously stated, prohibit the installation of an extended magazine tube. I suspect this was adopted primarily for the former reason.
In this post, I’ll show two different methods I’ve used to remove the dimples.
For reference purposes a schematic of the 870 Express can he found here.
Before we get going, let’s take a look at the disclaimer:
The contents of Rifleshooter.com are produced for informational purposes only and should be performed by competent gunsmiths only. Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.
Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.
Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.
Be forewarned, this modification will most likely nuke any warranty with Remington.
Method 1: The socket method
This is the most commonly encountered method you’ll see on the Internet. You find a long socket that you can slide into the magazine tube, hold part of it in a vise, and then use a punch to hammer out the detent. This method works fairly well, however, you need to be careful not to bend anything or misshapen the magazine tube. I’ve used it plenty of times and it has worked fairly well.
Method 2: Cut/drill out the dimples
This method is pretty straight forward. Since the dimples are under the barrel lug, you can simply cut them out to remove them and not worry about seeing them. Obviously dirt could potentially work its way in there, but for most users and most applications, it is a non issue.
I like to machine them out with a 3/16 4-flute end mill in a milling machine.You end up with pretty good looking results. A simple drill bit or rotary grinder would work as well if you don’t have access to a mill. The important part of this method is you use a file or some abrasive cloth to remove any burrs from inside the magazine tube.
With the dimples removed and an extended magazine in place, you still need a way to prevent the magazine extension from unscrewing since the Express barrel does NOT have a detent. Most people over look this and figure it out at the range when the newly installed magazine extension keeps coming undone. To address this you can clamp the magazine in place with a magazine/barrel clamp or to simply use a wavy magazine washer (I installed a detent into an 870 Express barrel once; I’m not sure it was worth the effort). I prefer using the washer (above).