870 'speed pumping' question

[hkr]

I took the recoil reducing stock I'm making for my 870 for its first live fire test yesterday. I noticed that due to the 1" of travel in the stock that the action opens on its own. This happens more rapidly with heavier loads and lower spring pressure, which makes sense. I recall someone on here recommending the proper form as pulling back on the forend, which also increases the effect, to the point where the action slams open with a fair amount of force when those three factors are combined.

I have a leak in the air spring that I need to fix, so that will help a bit once I can tune the operating pressure, so that it arrests the rearward motion just short of full stroke. If it's too low the gun is close to freely recoiling which exacerbates the effect.

So this 'speed pumping' (not sure if that's the right term) may be normal but is there a point when the action opening with too much force could damage something?

 

[870P]

I seriously doubt it, especially as the 870 is derived from an autoloading design, the 878 Automaster.

There's no practical way to make a pump cycle more violently than a semi.

 

[Dsiwy]

insure your 870 is clear and close the action, then pull back hard on the forend, at the same time pull the trigger and the bolt should stay locked until you let up reward pressure on the forend.

This is the factory test and if it passes your GTG and dont worry

 

[kennymo]

Nothing to worry about. My 870 action opens about a quarter of the way when I fire 3 1/2 super mags out of it. The setup is fairly similar to an auto loading action, I doubt it's humanly possible to rack it fast and hard enough to do any damage.

 

[hkr]

Cool, thanks for the reassurance guys.

Dsiwy, it passes that test, thanks for the info. I'm not worried once it's finished as it will be similar to existing products, just didn't want to break something during r&d. But now I know how to check!

 

[J.P.]

As said, no I don't think you can cycle an 870 too hard. If you don't want the action to pop open just push foreward on it while firing. This is my preferred stance - rear pressure on trigger hand pulling into my shoulder, off hand pulls foreward almost like trying to stretch the gun apart. It is a very effective way of controlling recoil.