Special thanks to Tactical887 for this review of the new ATI 7 Shot Fluted Magazine Extension.

The new ATI 7 shot fluted magazine extension, is not just all about aesthetics. It is constructed of military type 3 anodized, 6061 T6 aluminum. The standoff cap is designed for breaching doors, however the 7 shot extension runs fairly flush with the bore of an 18.5” barrel (see the first picture below).

New ATI 7 Shot Fluted Magazine Extension
New ATI 7 Shot Fluted Magazine Extension

If one were anticipating to use this extension as a breaching tool, then I would recommend you purchase the 8 shot extension. The 8 shot extension will protrude past the bore further than the 7 shot, making it easier to jam into door wedges. ATI makes an assortment of different end caps. If the standoff end cap (shown in the picture above) is not your style, ATI makes plain and swivel stud end caps.

New ATI 7 Shot Fluted Magazine Extension for Remington 870
New ATI 7 Shot Fluted Magazine Extension for Remington 870

ATI, incorporated a ratchet base for a tight fit. This is a nice feature because there is no need for magazine clamp, commonly found on the factory Remington 7 shot extension. I have fired about 100 rounds through my 870 with the new ATI 7 shot fluted magazine extension, and it did not loosen from the recoil.

Another advantage is that the extension runs flush with the shotgun barrel lug (see picture below). This gives the 870 a mean but yet unified look, the barrel lug would also supply extra support to the extension during the breaching process.

New ATI 7 Shot Fluted Magazine Extension for Remington 870
New ATI 7 Shot Fluted Magazine Extension for Remington 870

The advantages of the new ATI 7 shot fluted magazine compared to the Remington factory 7 shot magazine extension are like night and day.

Cons of the Remington 7 shot magazine extension:
A magazine clamp is needed in order to keep the extension from coming lose during recoil. The magazine clamp will scratch the barrel as well as the extension upon removal and reassembly. The magazine clamp is added weight and prolongs take down time.

The bayonet mount creates a smaller internal diameter which shortens the magazine spring and creates more tension, only allowing for six 2 ¾” shot shells to be loaded in the magazine tube and one in the chamber. Technically making the 870 have a 6+1 capacity. But when you think about it, it really is only a 6 shot extension even though it’s marketed as a 7.

Pros of the ATI 7 shot fluted magazine extension in regards to the Remington factory mag ext.
No magazine clamp
Military type 3 anodized, 6061 T6 aluminum construction
Fast take down time
Allows the magazine spring to have proper tension, the magazine tube will hold seven 2 ¾” shot shells and one in the chamber for a total of a 7+1 capacity.

on the right is the Remington factory 7 shot magazine extension
on the right is the Remington factory 7 shot magazine extension

ATI is stepping up their quality and their attention to detail. The new ATI 7 shot fluted magazine extension, comes in a nice foam padded box. At the bottom of the box are the installation instructions and the 7 shot magazine spring. For the small price of $50.00, with 2nd day shipping and $50.00 insurance, you can expect this magazine extension to arrive quickly. ATI has changed their designs, quality, packaging, 2nd day shipping with insurance and customer service, to provide a better experience for the consumer. With all the specifications I have listed above in mind, the new ATI 7 shot fluted magazine extension is a fantastic choice and a great addition to any Remington 870.

This magazine extension was discontinued by the manufacturer and no longer available.


  1. I recently added the 7-round mag extension and opted for the end cap with a sling mount instead of the door breacher. The extension runs about flush with the end of the barrel, which I find aesthetically pleasing. I still have the factory stock which has the sling mount at its base. I am only about 5’10”, so with a traditional sling the barrel of the gun is flush with my shoulder and the butt is down around my knee… which I don’t find comfortable or advantageous. I am looking at getting a different stock anyway and will probably get the side mount spacer that goes between the stock and receiver so I can use a single point sling. That said, I am overall very satisfied with the quality of the mag extensions. I just wish I would have opted for the door breacher. I find the article to be pretty accurate with the pros: easy take down, no barrel clamp necessary, exceptional packaging and shipping. Totally worth the $50 in my opinion. One thing I have not gotten around to is mounting a flashlight. I don’t know if the standard mounts that clamp onto the barrel and mag will fit since the diameter of this magazine is a little bigger, and I’m not really crazy about the integrated front ends. I would appreciate any feedback on the issue.

  2. I just purchased a Remington 870 Express with an 18″ barrel with the idea that I could add custom upgrades as I go. I love the positive feedback on the new ATI fluted magazine tube extensions, and although I don’t intend to ever use my shotgun for breaching doors, I love the look of the standoff end cap. The only issue that I would have, is that ATI 7 shot extension would protrude out past the end of my barrel, if yours pictured above is an 18.5″ barrel. Do you have any ideas on how I could make the end of the barrel flush with the standoff end cap? If its not possible, do the other end cap options extend a shorter length so as to be flush with the bore of an 18″ barrel?

  3. Brandon

    Matt, your barrel is most likely also 18.5″ unless it’s an older police model. If you order an 18″ from remington you will receive an 18.5″ unless you are leo. The actual measurements are taken from bolt face to muzzle, once installed you will have 18″ from receiver to muzzle and its a nearly identical overall length with this extension

  4. If you have an 18.5 barrel with a breaches on it if you put the 8 tube extension would it protrude or be even with the barrel?

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