Help me troubleshoot my 870...

[StealthyBlagga]

I have a brand new 12ga Remington 870 Express HD with the factory 6+1 mag extension. I like it a lot - surprisingly smooth considering it is at the budget end of the 870 range. I do, however, have one problem with it: during rapid fire (such as shooting pairs of clays), shells consistently fail to feed from the magazine. This happens only when I cycle the action rapidly (i.e. while still in recoil), and only with more than 3 shells in the mag tube (if I have 3 or less, the shells feed out just fine). So far, I've been shooting 2-3/4" 1oz, 2-3/4DE #8 shot target loads. With 3 shells in the mag tube, the follower should not even be to the join of the mag extension, so I doubt there is a problem there.

Before anyone suggests it, I am ABSOLUTELY CERTAIN that I am not "short stroking" the action. I owned my first 870 at age 17, and I am near 41 now, so I know how to pump these things very fast and reliably. The empty hulls eject smartly every time. Indeed, the problem happens even if I purposely pump to the open-only position. This is not operator error.

The shells feed OK every time if I leave a brief pause between firing the shot and pumping the action, so I initially assumed this was just a weak mag spring - in other words, the inertia of the stack of shotshells in the fully loaded mag was enough to allow the next shell to lift off the shell retainer momentarily under recoil, and so the shell was not released in the proper way. I have had this problem with my 8+1 shot 1187 too, and cured it with a Wolff +20% magazine spring.

Unfortunately, the +20% Wolff spring I installed today failed to cure the problem on my 870. I also tried a Choate mag follower (to reduce the chance of the spring kinking). I am therefore at a bit of a loss as to the root cause. I can't see any obvious burrs on the shell retainer finger. The only thing that I am still unsure of is that the mag follower feels just a tad rough for the first half-inch or so of its travel when I feed in the first shell, so there is a faint possibility of a rough mag tube interior, but given that there is no problem with a near-empty mag, I'm not sure I buy this explanation either (I'll check when I get the chance, none the less).

Can anyone else here offer any ideas/suggestions ? Hopefully someone else has had the same problem, and has a quick and cheap cure ready for me. I'd rather not have to take it for a long stay in a Remington warranty station if I can fix the problem myself.

I have my own Dremel, if this helps .

[Guest]

Thanks for the response.

The malfunction is a failure of the next shell to be released from the magazine. I pump immediately after firing the shot, while the gun is still in recoil, and the empty hull ejects OK but the next shell stays in the mag tube so I find myself with an empty chamber... click.

This is a factory 870 Express HD model; the +2 extension came with it, so I've never fired it without the extension in place.

Although I'm a bit skeptical about a hangup at the extension, I can't yet be sure - I'm going to check this week and test fire again at the weekend. I'm also going to closely inspect the shell retainer fingers and their action. I'll report back here what I find.

[Guest]

OK, I investigated this some more this weekend. I confirmed the root cause; as I suspected, the stack of shells in the mag tube is indeed moving forwards under recoil, and the rapid pumping is moving the right shell latch into position while the shell stack is still forwards. Thus, when the left shell latch (which should be holding the next shell ready to be fed) is pulled out of the way at the end of the pump stroke (which is happening correctly), in fact there is no shell there for it to release and so I get an empty chamber.

I am stumped as to the right way to fix this issue. I have another Wolff mag spring to try, but honestly I doubt this will help - the springs I have already tried deliver plenty of pressure IMHO. The real fix would be to move the cam position of the right action bar further forwards, so that the right shell latch is not actuated until later in the pump cycle. From what I can see, there is really no good reason for this latch to be actuated so early in the pump cycle (almost the moment the bolt unlocks). Have I discovered the long-hidden design flaw in the 870 ?

By the way, I did confirm that the right cam surface is in the "correct" position, or at least the same position as another new 870 I checked out.

I hope someone is going to tell me that this is a common problem for people who shoot their 870s fast, and that there is some gunsmith out there who specializes in fixing this problem by welding stock on the right action bar and cutting a new cam surface further forwards (later in the pump cycle).

Well, come on... don't hold back. Who is the gunsmith ?

[Guest]

OK, here is what I got back from Remington:

"Thank you for your patience. You could be experiencing shell surge. We make a magazine spring for police that is a little longer to prevent this. The part number is 92447 and retails for $3.25 plus $8 shipping and your local tax. You can order direct with a credit card at 800-243-9700 or check with local gunsmiths to purchase."

So now this phenomenon has a name... "shell surge". Sounds like exactly the problem I'm seeing.

Leaving aside that Remington apparently use a less reliable spring in their civilian HD model (presumably civvy lives are less valuable than LEOs), I've already tried using a Wolff +20% extra power spring, which is pretty darned stiff, and it didn't solve the problem. I've replied along these lines and an waiting for their further response.

Anyone care to comment ?

[joesquid]

I had the exact same problem with my 870. Tried all the things you did. Turned out it was one of the shell latches. Think I paid $8 for the part and haven't had a problem since. Here's a link to the parts breakdown.http://www.remington.com/pdfs/om/om_870.pdf

[gunnut69]

Shell surge only occurs if the gun is fired. Can you pump yours empty without a problem, without firing of course. If so you may well be experiencing shell surge. To counteract the remedy is a stiffer spring. Depending on the number of shells in mag and their weight spring tension will differ. Spring response is actually two factors, tension or the spring and it's length. For quick pumpers and heavy loads with high magazine counts the spring fills the tube at full compression and tension is quite high. If the gun won't pump rapidly then it's not surge its a bad shell stop, likely the primary or first step. It's also possible but less likely a bent action bar or damaged shell stop cam.. And just for the heck of it check to be certain the spring is not hanging up of the magazine extension joint.. That would result in rduced spring tension at a critical moment.