Nordic Components Spring Length

[Missa_Chin]

Hey everyone, new here, I just got my 870 a couple days ago ( ) and have already begun to make changes to it. One of the changes I had planned was to add a +2 Nordic Components extension to it however in travelling with it, it seems I must have misplaced the installation instructions for it. I heard the magazine spring has to be cut down to the appropriate length of the extension tube however I have no idea how true that actually is and if so what length it needs to be cut to or any additional details for that matter. I still have to drill out the dimples in the magazine tube but I was hoping someone could give me a hand in trying to figure this out before I start something I can't finish. Would be greatly appreciated if someone could help guide me through this, I've already tried searching online and haven't been able to find anything on it and haven't gotten back an email response from Nordic after about a little over a week now. Thanks a lot in advance.

[Synchronizor]

I'd say your best bet would be to contact Nordic. If you can't get through via email, their website gives a phone number for technical questions: 320-234-0329. That's a Minnesota area code, which should put it in North America's Central Time Zone (UTC - 05:00 until November).

You can also just measure your spring's solid length ratio and the internal magazine space in your build, and cut it just short enough to achieve your desired capacity. From there, you can remove a couple coils at a time to get the spring force down to whatever you prefer. If you'd like specific steps for this, let me know.

[aegusto]

If you'd like specific steps for this, let me know.

I'd love to know the specific steps if you don't mind.

[Synchronizor]

Well, there are a couple different ways to do it, but here's what I've come up with. You'll need a tape measure, two wooden dowels - one 7/8" and one 1/2" - and two half-inch fender washers.

First, measure your spring. Slide the untrimmed spring over the thinner dowel, then slide a washer onto each end of the dowel. Compress the spring all the way until it's at its solid length (the coils will be stacked right up against each other), and measure that fully-compressed length (you may need a helper for this part if you don't have monkey feet like me). Then, release the spring (carefully) and measure its relaxed length. Divide the relaxed length by the solid length, and the result is the spring's solid length ratio (which should be greater than 1, if it's less than 1, you did it backwards), which lets you work out how long to trim the relaxed length to in order to achieve a desired solid length.

Now, you need to measure the total space you have to work with in your magazine tube. Since Nordic extensions have removable end caps and no follower stops, this is pretty straightforward. With other extensions, this measurement often has to be taken piecemeal. Assemble the gun with all the magazine-related components you plan to use, except for the follower, spring, and extension end cap. With the gun's action open, insert the 7/8" dowel into the magazine from the front until it stops against the right (front) shell latch. Mark the dowel where it enters the extension tube (you should be able to simply indent it with your thumbnail), then remove it and measure the distance from your mark to the end of the dowel that you inserted. Add any extra space the extension's end cap contributes, and that's the total amount of magazine space you have to work with.

Now, measure the crimped length of the longest shells you wish to load without having reduced capacity, multiply that by the number of those shells you want to be able to fit in the magazine, and add any extra space that your magazine follower will take up between the end of the spring and the first shell in the tube. Subtract that figure from the total available tube space, and the result is the maximum solid spring length that will allow that capacity with those shells. Multiply the result by the solid length ratio you calculated for your spring earlier, and you should come up with the maximum trimmed relaxed length that will give you your desired capacity.

As the name suggests, this technique will give you the maximum trimmed spring length for your desired capacity. As such, the spring may end up stiffer than necessary. If this is the case, simply shorten it further, a few coils at a time, until you have it where you want it.

Before you actually do any cutting though, compare the maximum trimmed relaxed length you calculated to the total magazine tube space, and make sure that the spring will still be long enough to be compressed when the magazine is empty, and give a reliable amount of feeding force for that last shell. When in doubt, leave the spring longer; you can always make it shorter later on, but you can't add coils back once they're cut. You also may have to give up a shell in capacity with long-crimped or magnum ammo in order to ensure reliable function.



Hopefully that all made sense. It's going to be the subject of a video at some point, which should make the procedure easier to follow.

[Missa_Chin]

Thanks for the response Synchronizer, I'll definitely give your method a shot when I have some time again to work on it. Seems more complex than I expected but I'll take the time and figure it out and get the things I need, however if I run into issues I may just wait on that video unless I get a response back from Nordic. Ordering a replacement Nordic spring won't be the easiest task so I can't afford to screw it up. Thanks again and also the videos have been great, keep it up!

[aegusto]

Love your vids. Thanks for the info and keep up the good work!

[Missa_Chin]

Hey folks, finally got some time to work on it so I thought I'd just leave an update of everything. So I managed to hear back from Nordic and what they told me was that the spring should be placed in the magazine and from the end of the magazine extension (end cap off), should be no longer than 16" and if you would like less tension to gradually cut it down from there. Forgot to ask them what the shortest recommended length was however. So with that information I finally got to work on it, I proceeded to drill out the dimples and install the tube from there with no issues, dropped in a GG&G follower, installed the spring and snipped off the excess, capped off the extension and threw on a Magpul forward sling mount. Additionally, by cutting the spring I also realised the excess is just as long as the original factory spring that came with my 870 so I now have a spare spring for a 4 shot magazine. Everything seems to be in working order, I ran some snap caps through it after the install and it was feeding just fine. Friday I managed to fire the gun for the first time and aside from one occasion with a slight hangup with the spring somewhere in the magazine tube (slight tap to the side of the gun fixed that) it performed great, however, I will keep an eye on that. The only other issue I experienced was the action locking up, however I doubt that had anything to with the extension but more with the machining marks in the chamber that I read on, so I have another thing to add to the to-do list. Anyways, even though my experience with everything is limited, so far I'd have to say I'd recommend this, the design looks great, weight is minimal and construction feels solid. No regrets on this purchase at all aside from the fact that I probably should have gone with the +3 extension tube, but thats no fault of the product of course so I'll be looking into getting the tube only next time I'm buying.

Drilling out the dimples.

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New GG&G follower.

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Finished!

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[Torbay]

I installed the full length 45" NC in a 4+3 tube extender. Fit quite good, 7 shotshell full capacity , just be careful with your eyes installing , but still the shell surge is not solved ( damn shotgun !!!!! )

[Synchronizor]

Friday I managed to fire the gun for the first time and aside from one occasion with a slight hangup with the spring somewhere in the magazine tube (slight tap to the side of the gun fixed that) it performed great, however, I will keep an eye on that.

That hang-up is more likely due to the follower, not the spring. Triple-bearing-band followers like the GG&G or Vang Comp can be less reliable than other types when it comes to dealing with the joint between magazine tubes & extensions. I would suggest putting your factory follower back in and seeing if you can replicate the jam.

The only other issue I experienced was the action locking up, however I doubt that had anything to with the extension but more with the machining marks in the chamber that I read on, so I have another thing to add to the to-do list.

What ammo were you using? And did you clean out your barrel's chamber before you took the gun shooting? Stuck shells are much more likely to be the result of low-quality ammunition and/or dirty chambers than defective machining. Stuck shells are more likely in a brand-new chamber, but the best remedy for that is usually just to shoot your gun a lot to break it in.