Rem 870 ext mag capcity for 20"bbl ?

B

bamaranger

New member
What mag capacity should I be seeing in a Rem 870 w/ 20" bbl and matching ext mag w/ a stem type tac mag follower?

At the range other day, such as above would only hold 6 rds in mag. My 18" 870, w/ matching ext mag and a tac follower, also holds 6. Something is not adding up.

Shouldn't the 20" gun be a 7+1 proposition? Maybe 8 + 1 with the basic factory follower?

Dissassembling mag and reassembling, and std factory follower, still yield only 6 rd capacity in the 20" gun. What's going on?
 
Off the top of my head, the 20" barrel is only 2 inches longer and the shells are 2 1/2" to 3" long. Extending the mag well may get you one more shell, but may be just a little short. I know they make the longer mag extensions, but have not compared the size to barrel length.
 
I've had a Rem 870 20in with extended mag for nearly 20 yrs.Mine holds 7 2 3/4 in shells in the mag.I dont know what it would hold with 3in as it is chambered for the shorter shells,but I suspect it would only hold 6.
 
closer look

I pulled the mag tube and spring and compared it to the one in my 18" gun.
Big difference in the springs. The suspect 20" spring is much smaller dia and heavier gauge. It is most likely not compressing as easily or compactly.

The 18" spring is greater dia and lighter gauge. I have some other ext mags springs around, and will swap them in and out on the problem 20" gun and advise.

This is all with 2-3/4 " shells.
 
Make sure after your spring swap that the gun feeds reliably.

How much short of getting that 7th shell in the magazine are you? How much of it can you see when trying to push it in?

This may be resolved with an ammo swap. 2 3/4" is the length of the unfired shell. There's some variance in loaded ammo based on amount of powder, shot, wad design, etc.
 
Follower, spring, and type of shell matter. My 20" 870's with +3 extensions hold 7 Federal LE12700 shells just fine.
Click to expand...

Very true. Aftermarket followers are often "better" but the cost is that they often take up just enough more space in the tube to prevent loading the last expected shell.
 
I have read that some manufacturers of "magazine extensions" will use the same lenght spring for two sizes of extensions and to get the extra shell into the shorter of the two extensions you may have to cut the spring a bit.
 
In my experience you sacrifice one round to the wilson follower, unless you modify it by trimming the stem down a little.
Click to expand...

I like that follower, but that's been my experience in every shotgun I've ever put it in. In addition, in a Benelli Nova/SuperNova, it will cause feeding problems if the muzzle isn't at least as high as the breech (YMMV on that one).
 
And that may very well be the issue. Never used Wilson extensions. But with the Remington factory extension and this follower, expect to trim about 1/2 to 3/4" off the stem to get the full capacity of mag tube+extension.
 
The Factory tube extension limits the capacity with the press in ring for the mag clamp screw. It stops the follower from passing.

Factory tube ext - 18.5" barrel 6+1, 20" barrel 7+1

Non factory tube ext design and even with the muzzle - 18.5" 7+1 capacity, 20" barrel 7+1, 20.5" or 21" 8+1 capacity.


GC
 
Not yet

I can't say how many shots its supposed to have, that's the purpose of the post, to determine same. The extension is flush with the muzzle of a 20" bbl. I am willing to accept, and understand that a long stemmed follower may rob me of one round, but I feel like the rig is likely 2rds short in capacity.

Have not checked it further, but here's some more history. The 20" gun had the std stubby, hollow, cup shaped follower in it. I see the shooter load, he gets 6 in tube, and no more. He says thats all he's ever been able to get in it. I figure the spring is binding and a good tac follower will help.

I locate a Scatter Gun Tech follower, pretty short stem, bevel the back edge so it won't hang, install same, and still only get 6 in the tube. Hmmm?

The 20" spring looks very heavy and much different from the one on my 18" gun. The 20" spring would almost have to be stock/factory. Oddly, one of my thoughts was that it was for a 24" gun! I have some other springs about w/ the same appearance. I may cut 2-3/4 off one and see what I get, both function and appearance wise.
 
Here's a wilson +2 on my 20" barrel. It holds 6 +1 every time with the wilson follower.

P1020115-1.jpg
 
problem solved

OK, got back w/ my shooter and the problem magazine. Took an extra spring, cut successive coils off, to the point reliability would suffer, at the last it took 7 rounds, but the solution was not a good one.

What is going on, thinks I? I studied the mag extension tube and finally shined a light into the darn thing. Hmm? Seems like there's something up there at the groove for the clamp and swivel bracket. A quick check shows that ANY mag spring WILL NOT go all the way forward to the end of the tube. There's about a shell length of tube setting there empty, 'cause the SPRINGs can't get all the way forward. They catch there at the groove. What is that thing, this doesn't seem right?

I took a small dia rod, and by entering through the drain hole (?) at the closed end of the tube, rapped the obstruction w/ the rod and a hammer. It moved readily. Again, and again, and now it's visible at the threaded end of the tube.

I recognize it right away. Its the darn "cap" used to hold the std 4rd mag spring in place when there is no extension on the mag/gun. Some DOLT added the extension and didn't know what they were doing. They installed the extended long spring, topped it with the "cap" , fitted the extension on, and screwed the whole assembly in place. The "cap" would not pass the groove in the ext used for the clamp/bracket, and thus neither would the spring......so it was always near 3" short in room in the mag tube and one round short.

Pull that stupid cap out!!!!!! The shooter pleads ignorance. "I was issued it that way". OK, maybe he was. I can't say other wise. Install a new ext. spring, suitable for the ext tube. Back in goes the SGT tac follower. Seven rounds snick in no problem.

The whole process took about an hour, I reduced an extended spring to std size trying to trouble shoot the problem, and lost some more hair from my bald head. But now its right.
 
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