870 Bent Carrier - Causes shells not to feed?

[marklbucla]

This is a followup to this thread:
http://www.thehighroad.org/showthread.php?t=179471

I've noticed that the carrier is leaning to the left side of the receiver and even scrapes against the side. (The side opposite the one with the loading/unloading port on it). Would that be a cause of the shells not coming out of the magazine tube? Can the carrier block off something that's supposed to let shells out of the mag tube?

Now, it's the first few shells that won't come out of the extended magazine reliably, but the spring and follower have both been replaced and the whole gun cleaned thorougly. I also used a different brand of ammo. If I shoot and wait to cycle the action, it's fine. If I pull back on the forend as I'm shooting, it starts to jam up. It used to work perfectly, but since the winter break, it's been totally unreliable.

 

[dfariswheel]

No, the lifter has nothing to do with shell release.
Some Express guns do have shell lifters that are slightly misaligned to one side enough that a few do drag a little.

I don't know if this will help, but here's how the 870 works:

Notice that on the action bars are small "ramps". One on the left bar is pointing to the rear, the one on the right points forward.

When the fore end is moved to the rear, the LEFT action bar's ramp pushes the left shell release outward, releasing the shell in the tube.
The magazine spring pushes the shell into the receiver.

When the fore end is pushed forward, the RIGHT action bar's ramp pushes the right shell lifter outward, and this allows the next shell in the magazine to move rearward slightly, until it's caught by the LEFT shell stop.

This process "hands off" the shell from the Right shell release to the Left release, then releases it into the receiver.

When the fore end is pushed to the rear, the shell release should move outward, and the shell should be pushed into the receiver with a considerable amount of force.
When the fore end is pushed forward, the next shell should "snap" back slightly and be caught by the Left shell release.

First, if the shell releases are functioning properly, and the spring is good, SOMETHING is binding or otherwise interfering with the magazine system.

Here's some things to check:

Start from the basics, and work your way forward.

First put the gun back into original condition by removing the magazine extender, replacing the original short magazine spring, replacing the barrel and screwing the magazine cap down hand tight.
Load the gun and test for function.
If it works properly with the original 4 shot magazine, the fault lays somewhere with the magazine extension and/or how it's working with the gun.

Remove the trigger assembly from the gun for these tests:

Remove everything from the receiver. The barrel, bolt assembly, fore end assembly and magazine extension assembly.

Check the extension and it's collar for out of round or squashed areas, an extension that's out of line, or canted when mounted on the gun, with and without the barrel.

With the extension off the gun, and the spring out of it, drop a few shells into the extension to check for sticking or jamming shells.

Attach the extension to the gun MINUS the barrel.
With the spring and follower out, load the magazine with 6 rounds to check for sticking or binding by pointing it upward and operating the shell released by hand.
The shells should feed through even with NO spring in the magazine.

Do this again with the barrel ON the gun but no spring or follower.
What you're looking for is to check if non-spring loaded shells will stick or jam in the magazine.

Replace the spring and follower but leave the barrel OFF.
Load the magazine and test for function by operating the shell releases by hand.
Press the left release, and a shell should be ejected from the magazine.
Press the right release, the next shell should move to the rear and be caught by the left release.

Replace the bolt and fore end assembly, replace the extension assembly and test for function again by pumping the action with the barrel OFF, and again with the barrel ON.

By doing this Trouble Shooting process one step at a time, you should be able to find where the problem is.

 

[Fred Fuller]

Nope, the lifter shouldn't be the cause of the feeding problem. Note I didn't say _couldn't_, because there is a slim possibility it might, but the lifter should be all the way down and clear of the magazine tube when the action is going from closed to open as the gun is cycled.

Try pushing FORWARD on the fore-end, and pulling back on the pistol grip to seat the gun on your shoulder as you fire. With some 870s if there is hard back pressure on the fore-end when the gun is fired, the forearm has to be moved forward toward the muzzle just a bit (as recoil would do, if the gun were not deathgripped with back pressure on the forearm) to allow it to unlock the action. It might not be a mechanical problem with that aspect of things at all, but a matter of technique.

As to feeding problems when the gun is not fired- still having problems with that?

lpl/nc

 

[marklbucla]

I still have to investigate the other possibliites mentioned before, but I can say that the gun always cycled fine before the Winter using my "Deathgrip" techinque.

Holding the action release and cycling rounds quickly works okay too.

I originally decided to migrate towards the 870 over my 500A because the action is much smoother, but if I have to slow down, then I may as well go back to the 500A.

 

[Fred Fuller]

There are four 870s I can get to here without opening a safe, two Expresses of unknown manufacture dates, a Wingmaster (1976) and an 870P (1989), all used to various degrees. Of the four, NONE of them will open the action when the hammer drops if the fore-arm is being pulled firmly to the rear at the same time. After I experimented a bit I checked into what Jerry Kuhnhausen has to say in _The Remington Shotguns: A Shop Manual_ (VSP Publishers, 1992). On page 21, in the chapter titled "Remington M870 Cycle Of Operation" it says:

"...Just before the firing pin is struck, the hammer plunger, in upward motion, engages the action bar lock. Movement of the front of the action bar lock downward is restrained when the forestock is held tightly rearward. [emphasis mine] The action bar lock is freed when pressure against it is briefly and involuntarily released by the shooter as the shotgun recoils rearward. ..."

Sorry to say it, but it is beginning to sound as if that particular aspect of your problem isn't mechanical in nature. I would say it's likely that over time your technique has evolved into a firmer pull on the forearm than was previously the case when the action released upon firing under recoil, rather than that the gun has developed some sort of action problem. After all, it seems to be working as it was designed and intended to work.

The technique of pushing forward on the forearm while pulling back on the pistol grip to seat the stock firmly on the shoulder is taught by some instructors to help control recoil and thereby speed recovery from the shot, I have never noticed that it demonstrably slowed down cycling the gun. I suggest a shift in concentration to hitting with the shot being fired, rather than trying to force the next shot with all possible speed. Try it and see if it helps...

lpl/nc

 

[marklbucla]

I would say it's likely that over time your technique has evolved into a firmer pull on the forearm

Technique wise, I'm doing the exact same thing I've been doing for years, but I have been working out a lot more lately and I have been seeing results. You're right, that's probably it. And if I do shoot then rack, it's 100% reliable.