S & J spring length

[Reaper]

I purchased a couple of your followers and one of your 750 mm springs. Planned on using it with a +3 extension, but have since decided to use a +2 extension instead. I need to know how long the spring should be with a +2 mag extension on my standard magazine (4) 12 guage 870. Thanks.

[Synchronizor]

What brand of extension are you using this spring with?

[badboybeeson]

I purchased a couple of your followers and one of your 750 mm springs. Planned on using it with a +3 extension, but have since decided to use a +2 extension instead. I need to know how long the spring should be with a +2 mag extension on my standard magazine (4) 12 guage 870. Thanks.

There are a lot of factors in this
what length of shells are you using?
what brand of mag tube?
I would start with the spring 4 inch longer then the end of the factory part of the mag tube and then test and trim to size
bbb

[Reaper]

I bought this extension probably 20+ years ago, can't remember the brand to be honest. It looks like what is now called Tac-Star maybe?

I only use 2 3/4 shells.

[Synchronizor]

Have you tried using the spring as-is? If you're only loading 2.75" shells, you may not need to shorten it at all.

[Reaper]

The 750 mm S & J spring as stated on the website will work with up to a 9 round total mag extension, its long! Website also says spring may have to be cut.

No, I haven't tried it yet with the +2 round extension. I just figured it was too long to even try with a
+2 mag extension.

[Synchronizor]

I'd give it a try, you might be surprised.

2.75" shells are usually somewhere in the ballpark of 2.3" - 2.5" crimped. That extension looks like it'll give you roughly 18" of interior tube space (assuming that's an 18.5" barrel). Subtract the length taken up by 6 shells, and you should easily have 3" - 4" of room left over for the follower and compressed spring. This is all some fairly rough eyeballing and napkin math, and the specific shells you use can change things a lot, but it sounds to me like there's a good chance you'll have your desired capacity without cutting anything. It might make for tough assembly and stiff loading, but at least you'll know you can trim it down to your preferred stiffness without having to worry about capacity. Even if it is too long to let you get that 6th shell in, you'll be able to easily measure the spring's excess solid length, and work out the minimum amount you need to cut off from there.

I wish spring manufacturers would be more willing to specify the geometry and stiffness of their springs. That would let us work out the proper length with just a calculator.

[12GAfun]

I am using a Remington +2 shot kit with the Cholate +3 kit spring and S&J follower. It feeds all 6 into the tube without issues.

[BlueSmoke]

Try the spring full length first.

Check capacity of the magazine tube by loading it with shells.

I would only choose to cut the spring shorter....if I could not load the tube to expected capacity.