Anyone measure their mag spring length ?

[palehorsecometh]

Have any of you guys measured the mag spring, I have an 870 tactical 7 shot. After 4 months of keeping it loaded with 5 rds. in the mag and it holds 6, I took the factory spring out and it measured 18 inches. There was very little tension when I loaded the mag and it did not even want to jump out of the mag when I removed it. I ordered a wolff spring and that one measured 31 inches that's a big difference in length. I had to force the new spring in and there is a lot of tension when I load it now. It's hard to believe that much length difference between the two springs.

[Synchronizor]

Spring tension isn't just about uncompressed length, it's also affected by the spring material itself. Also, springs tend to wear out due to compression cycles more than time spent compressed.

The spring I use with my +2 and +3 extensions is about 26" in length. The spring I use when I'm not running an extension is about 15"-16". 18" sounds very short for a 6-round mag tube. Is your 870 a standard gun with a +2 extension, or is it one of the specialty models with the one-piece 6-round mag tube?

[palehorsecometh]

It has the one piece tube that stops about two inches from the muzzle. I've had two with the factory ext, but this one is a one piece tube that holds 6 rounds. It says 870 tactical on the receiver.

[Synchronizor]

Well, that may explain it. My 870 has a standard 4-round mag tube, and then I install extensions for different builds. For those models, Remington has one spring that it uses for both +2 and +3 extensions which is about 26" long. The Wolff spring you purchased is likely intended for those magazine configurations as well.

I'm not sure what the length of the factory spring is for models with the 6-round mag tubes, but I have measured the tube itself in a gun shop. It extends about 16.25" from the front face of the receiver. Add in another half-inch or so for the section inside the receiver and subtract a little to account for the follower, spring retainer, and magazine cap; and a magazine spring with a relaxed length of 18" doesn't sound too unreasonable, as long as the spring wire is stiff enough.

Were you actually seeing feeding problems with your gun, or were you just concerned that the spring seemed short?

[palehorsecometh]

No feeding problems I just noticed the shells loaded much easier than they ever have in a pump. Also when I took the the spring retainer out the spring just stayed in the mag and I've always had them spring out under a fair amount of tension. I installed the wolff spring, loaded it up and it feeds just fine. I'll keep the factory as a back up. Thanks for all your help and take care !

[Kentactic]

Sounds like your spring was the wrong size if it didnt pop out of the tube. But measure that wolf spring after it sits loaded for 30 days, It will have shrunk. They break in pretty quickly and lose a few inches but it will still have a decent amount of length over the mag tube size. On a side note ive kept my +2 express loaded with all 6 rounds for a couple years and its still got pleanty of tension all the way to the last round.

[MStarmer]

Isn't there a rule of thumb when trimming a long spring? I'm trying to think back from memory when I installed my Nordic extension/follower/spring on my Benelli. I'd have to see if I could dig it up but I though it had a minimum measurement of 12" to 18" past the stock tube. Then you check load and see how may you can get it, if it's tight you trim a little. Brownell's, or Aippi (J.D) should have some recommendations I would think. I'd say for a pump gun you have quite a bit of leeway in spring force / length. I know the spring in my 870P is fierce with just the 4rnds in the tube. In fact it leaves significant impressions where the bottom shell is sitting on the shell stop.

Here's one of the articles... I like the Nordic springs, they have a great feel/coating etc...

http://www.stu-offroad.com/firearms/nor ... /mag-1.htm

[Synchronizor]

The 4-round Police models use an extra-heavy spring.

There's no universal set of rules for trimming a mag spring. Coil pitch and wire stiffness will vary between manufacturers, so trimming a certain amount off a spring from one manufacturer will have different effects than cutting a spring from a different manufacturer to the same length. Also remember that you have to remove a lot of uncompressed length to get even a tiny change in the solid (fully-loaded) length. Unless that last shell is just barely shy of clicking past the shell latches, or you have an overly-long spring to start with, trimming the spring should be a last resort.

[12GAfun]

The 4-round Police models use an extra-heavy spring.

There's no universal set of rules for trimming a mag spring. Coil pitch and wire stiffness will vary between manufacturers, so trimming a certain amount off a spring from one manufacturer will have different effects than cutting a spring from a different manufacturer to the same length. Also remember that you have to remove a lot of uncompressed length to get even a tiny change in the solid (fully-loaded) length. Unless that last shell is just barely shy of clicking past the shell latches, or you have an overly-long spring to start with, trimming the spring should be a last resort.

I have a 870 Tactical Express with that tactical choke door breach choke tube and the spring on my Remington mag kit was 26.5" long but it broke in the tube and is now 20" and I have loading issues it will load all 6+1 then all of a sudden it will only hold 4-5 shells I just saw a video that there could be a gape in my extension tube but when it worked it still feeds those shells fine and reloading is a breeze with the 20" spring when it does not hang up on me. I will try what I watched in a video about installing that extension kit and see if it was hanging up on a gape in the tube.

[Synchronizor]

If it's not an installation issue, the next likely cause is the bracket. Are you using the factory extension bracket or an aftermarket clamp? Or nothing?

If you're using a factory bracket, you may have ended up with the wrong type. I've heard that some 3rd-party retailers are selling extension kits with brackets that don't have the right spacing between the barrel and the tube. When installed, these brackets will put force on the extension tube, opening a gap in the coupling. I've been told that the correct brackets will have an "X" stamped in one side.

If you're using an aftermarket clamp, you could have the same problem. Not all aftermarket add-ons are designed very carefully, and some products get the spacing wrong.

If you're not using a bracket, you need to. Two-piece extensions like the factory Remington kits are not intended to be used without a bracket. Without one, the tube will back off under recoil, opening a gap inside the magazine that can cause hang-ups.