Put on a magazine extension for 12 ga rem 870

[thereddog]

Evening all,

I got a remington made 3 cartridge magazine extension for my 870. It only has an 18 inch barrel though, so I can only get a total of 6 in the magazine and 1 in battery.

Does anyone know why an 18 inch barrel would limit me to just 2 extra cartridges in the magazine instead of 3? It doesn't make sense to me.


The stock follower is working properly and the cartridges do not hang up where the extension meets the rest of the magazine (I had that trouble with a different extension that I decided to send back.)

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[Joe13]

It's not the barrel it's the extension.

Are you for sure it's a +3 and what was it to start with?

I have a 20" barrel and my tube extension is flush with my barrel and gives me 6+1.

 

[DirectDrive]

Evening all,

I got a remington made 3 cartridge magazine extension for my 870. It only has an 18 inch barrel though, so I can only get a total of 6 in the magazine and 1 in battery.

Does anyone know why an 18 inch barrel would limit me to just 2 extra cartridges in the magazine instead of 3? It doesn't make sense to me.


The stock follower is working properly and the cartridges do not hang up where the extension meets the rest of the magazine (I had that trouble with a different extension that I decided to send back.)

Probably because most users don't want the mag tube extension hanging out beyond the barrel.
It should be nested under the barrel for protection from impacts, etc.
Therefore, Remington makes a +2 extension for an 18" barrel application.
Remington 18 in. Factory Magazine Extension Kit Model 870 +2 Shots Blued | Natchez (6+1)
Remington 20 in Magazine Extension for Model 870-3 Extra Shots Parkarized | Natchez (7+1)

 

[HB of CJ]

We added homemade mag extension tubes to our old Rem 11 shotguns. I forgot the barrel length. May have been 24 inches. Ended up with 8+1. When fully loaded the mag tube still had about 1 inch of free travel. Could not squeeze in 9. Thin wall steel tubing of the correct inside diameter. High temp silver soddered to the stock mag tube. The mag tubes free floated. Recoil operation. Worked great. Thumb tang safety. Not an 870 but close to the same fun upgrade. Wish I still had those shotguns. Sold them years ago. Or were they traded off? Forgot. Old Coot.

 

[thereddog]

Yhis one is the 3 cartridge extension and it does indeed stick out a couple of inches from under the 18'' barrel.

It is supposed to hold 7 cartridges in the magazine with it, but it only holds 6. I am not sure why having a barrel that is 2 inches longer than the current one would somehow magically allow the same extension to handle another cartridge... That makes no sense.


What am I misunderstanding?

 

[DirectDrive]

2-3/4" shells ?
Maybe the spring is stacking ?
Something in the tube like a waterfowl plug ?

 

[thereddog]

Everything in the magazine is freely cycling with the pump, It is not catching where the tube extension meets the magazine. The detents are drilled out, the follower is doing its job, and the black plastic apparatus that is at the distal end of the interior of the magazine is still in place. I wonder if I should remove it from the equation?

The cartridges are 70mm

 

[DirectDrive]

Everything in the magazine is freely cycling with the pump, It is not catching where the tube extension meets the magazine. The detents are drilled out, the follower is doing its job, and the black plastic apparatus that is at the distal end of the interior of the magazine is still in place. I wonder if I should remove it from the equation?

The cartridges are 70mm

When I look at that extension, it's got that "indent" a couple of inches from the end.
The follower must stop there and then the remaining space after the indent must be where the spring stacks.
If there is something in that last few inches of tube, then that could be what is reducing your capacity.

 

[CHLChris]

Ding ding ding! I have the answer!

Not every 2-3/4" shell is the same length. I have a few 00buck brands that are just a smidge longer than others. They only allow 5 in my rig just like yours. I decided to use the shorter ones I also had. Now I get 6. Never have been able to get 7, though. That would require over an 8 inch extension tube and there just isn't room. I have a plus-2 and it goes almost flush with my 18" barrel. Only 6 shells.

 

[thereddog]

I am running the Cheddite super t5 (70mm) #4 buckshot cartridges in it, I will try with some winchester trap loads and see if it likes them better. 12 Gauge Ammo | AmmoExpress.com

 

[CHLChris]

Oh, also one more thing to look at, the spring o ly needs to extend like 8" longer than the whole tube. Any chance your spring is too long?

 

[thereddog]

I am not sending this extension back, I've already done that once. The barrel clamp where the sling swivel is is secure (although I barely had room to mount it.) I know it looks a little odd with that extension being longer than the barrel, But noting is ever perfect.

 

[thereddog]

the spring is the one that came with the extension (it is OEM Remington stuff) so I'd assume that they sent the appropriate spring.

 

[bbbass]

I don't have an 870, but I'm wondering why not replace the entire tube with one that holds 6 or 7???

 

[thereddog]

The 870 was able to hold 4 (@70mm length) in the magazine prior to the extension. The extension indicates that it accepts 3 more cartridges, but it is only taking 2 at this point. The rem 870 platform is akin to the AR Rifle platform and the Ruger 10/22 in that it offers all kinds of different configurations and add ons to customize.

 

[Stomper]

the spring is the one that came with the extension (it is OEM Remington stuff) so I'd assume that they sent the appropriate spring.

Don't a$$-u-me that. It could be that the kit was designed for a longer OEM mag-tube, like a 5rnd capacity and came with a longer spring, which would explain your issue. You said your OEM held 4+1, so I would take the above advice and see if the new spring is beyond 8" of the OAL of your assembled extended mag-tube.

 

[CHLChris]

the spring is the one that came with the extension (it is OEM Remington stuff) so I'd assume that they sent the appropriate spring.

The extensions that I've bought have always come with springs that are "too" long. There are videos on YouTube showing how to determine to what length you should cut them down (just a simple wire cutter is necessary). If, placing the new spring next to the entire mag tube, the spring is more than 8-10" longer, I'd cut it down. You could get just enough extra room to fit the 7th round.

Question: How much room is left when you press the 6th round as far in as it will go? Almost enough for a 7th round, but just wee bit short?

 

[bbbass]

And then there's this:

 

[Stomper]

And this....

 

[thereddog]

OK, This is the advice I needed. I recall that the spring took a fair amount of wrangling to get into the new set up. I recall it being well over 8 inches longer than the overall magazine.

It sounds like the proper excess of spring should be appx 8 inches longer than the full length of the magazine... Yes?

I appreciate your help. You guys always have always pointed me in the right direction.

Man, that double stack Magazine is fierce. The setup must weigh several pounds...