Opinions on 870 FTF problem after stock change

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platnumbob

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I have put the final touches on an 870 build I have been doing but have now discovered an odd failure to feed problem out of the mag tube. The gun started as a express super mag I have had for years (with no FTF issues) but now wears old police wood and a 12.5 norc barrel.

On doing some function checks the shotgun will not feed rounds out of the tube and into the chamber unless I pump quite hard and turn the forearm inwards/ left. Not doing this results in no rounds exiting the tube. I switched the old forearm on and the barrel back just to see if it makes a difference and it does not. Is it possible I bent the forearm metal rails just slightly causing this to happen? (It would be minor since it goes together fine) Any other possibilities? Never heard of this problem before on an 870.

Thanks!
 
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I had this problem with a Norinco HP-9. You have to really slam the action open to get rounds to feed from the tube? The staking had come loose anyways so I removed the shell interuptor and bent it a little to clear the rim of the shell. To check if this is your issue, pop a round in the tube and gently open the action all the way. If the interuptor is still hung up on the rim of the shell but is moving then it should just need a small tweak.
 
It's possible the slide arms are bent out of parallel, but this should be an easy visual check.

Also, are you sure the action is opening all the way? I've never tried it but many 870 stocks say on the package they are not compatible with super mag actions.
 
Thanks for the comments. Gwhysow, don't think it's the stock tension bolt- nice and tight.

Claven2 the slide arms look visually fine. I also don't "think" it's an issue with the new fore-arm not being compatable to a super mag because the issue replicates itself when I switch back to the original fore-arm.

I just played with it again and with no barrel or bolt the mag tube will feed out pretty reliably. Also both of the little hands seem to move back and forth which I believe to be the motion allowing shells to exit. Once the bolt / and/or barrel are installed it will feed only with a decently hard rack and as above, only when I am twisting the fire-arm inwards/ clockwise a bit.

This may be in line with the loose staking issue supernova mentioned. Where are these hands / shell interrupters staked? How are they removed- do they pop out easily when the trigger pack comes out? Would I bend both or just the one on the non- ejection side?
 
platnumbob said:
Thanks for the comments. Gwhysow, don't think it's the stock tension bolt- nice and tight.

Claven2 the slide arms look visually fine. I also don't "think" it's an issue with the new fore-arm not being compatable to a super mag because the issue replicates itself when I switch back to the original fore-arm.

I just played with it again and with no barrel or bolt the mag tube will feed out pretty reliably. Also both of the little hands seem to move back and forth which I believe to be the motion allowing shells to exit. Once the bolt / and/or barrel are installed it will feed only with a decently hard rack and as above, only when I am twisting the fire-arm inwards/ clockwise a bit.

This may be in line with the loose staking issue supernova mentioned. Where are these hands / shell interrupters staked? How are they removed- do they pop out easily when the trigger pack comes out? Would I bend both or just the one on the non- ejection side?
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My wingmaster was doing the same stuff, once I had my gunsmith re stake the shell latches it ran perfect.
 
Staking should not be an issue. One of the trigger assembly pins goes through both the shell latches and once installed, the trigger guard prevents them from being able to "pop out" of the staking. It's possible one or more is bent, but if it's a new gun, that would seem unlikely.

The idea that "twisting" the fore-stock clockwise (as seen from the shooters perspective) as you cycle it changes the performance, would seem to indicate the right latch is the one giving issues, but that latch only serves to prevent double-feeds.

The 870 releases shells: At the first part of the rearward slide travel, the left latch which is further forward, retracts and lets the shell slide back and the right latch prevents the next round from double-feeding. The slide arms have a bevel on them where the slide arm gets taller. This bevel hits a "tit" on top of the latch, up forward by the magazine, making it retract. It sounds like it's this part of feeding from the magazine tube that is giving you grief.

So either the bevel is too high and not hitting the "tit" on top of the latch, or the latch has a broken or worn "tit", or the latch is not retracting into the side of the receiver far enough.

Hard to know more without seeing the gun in person - sorry. But based on what you are saying, I would slowly cycle the action with the trigger mechanism REMOVED and see if you can spot when the left and right latches retract. Then try it again with a snap cap or dummy hull in the mag and watch to see if the left latch retracts enough for the shell to move backward from the mag.
 
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The staking is at the rear of the interuptor/shell stops near the trigger group pins:
20160221_172537_zpsuz79ytvt.jpg

20160221_172549_zpsqktbf02n.jpg

Now when the bolt is out of battery, the interuptor (left) catches the next shell. The shell does not touch the shell stop (right) yet.
20160221_172853_zpsglfbkdtc.jpg

Now when the bolt is coming into battery, the interrupter is pushed to the side allowing the shell to pass by and be caught by the shell stop.
20160221_172908_zpso6lybw0z.jpg

Now when the action is fully opened, the shell stop is push into its groove allowing the shell to feed into the action and onto the elevator. The interruptor is no longer held back so the shell slides along it until it catches the next shell. I pushed this hull forward to show what the shell stop should be doing.
20160221_172939_zps1nsngwha.jpg

If either of these parts are not moving fully out of the way you can end up with the feeding issue you describe. With the bolt closed in battery there should not be a shell caught by the interruptor. When the action is gently opened all the way to the rear, the first round in the tube should be released into the action. Check the position of both parts as you cycle hulls through the action and you should be able to determine if thats where your problem is.
 
First off I have to say, once again, that the people on this forum are top notch. Amazing thanks.

Supernova these were helpful pics, I removed my trigger group and am pretty certain my staking is fine- everything seems to be in there tight. With that said i seem to have periodic issues with the last stage of the shell feeding process, that is, what you describe as the shell stop (right side in pics) does not seem to always fully get out of the way of the shell rim.

I don't want to remove these arms since they are staked in, but would you guys recommend just tapping the shell stop finger in towards the receiver a bit with perhaps a punch and hammer? Might be kind of hard to angle in but it seems potentially doable.
 
Glad to hear the problem has been isolated. After rereading your OP, the action is all original and just the forend and barrel were swapped? I would have a good look at the action bar on the shell stop side as well as the stop itself for wear along with making sure there isn't a buildup of crud behind the stop. I only bent mine because it was a brand new shotgun and the staking was done improperly causing the shell stop to fall out when I first pulled the trigger group. Norinco wouldn't warranty it because I didn't buy it from one of their distributors. At this point you could try either replacing parts or slightly modifying them. Personally I would dig deeper to try to find the exact cause of the problem to make the most informed decision.

platnumbob said:
First off I have to say, once again, that the people on this forum are top notch. Amazing thanks.

Supernova these were helpful pics, I removed my trigger group and am pretty certain my staking is fine- everything seems to be in there tight. With that said i seem to have periodic issues with the last stage of the shell feeding process, that is, what you describe as the shell stop (right side in pics) does not seem to always fully get out of the way of the shell rim.

I don't want to remove these arms since they are staked in, but would you guys recommend just tapping the shell stop finger in towards the receiver a bit with perhaps a punch and hammer? Might be kind of hard to angle in but it seems potentially doable.
Click to expand...
 
Yes the gun itself has had little meaningful change and the problem is replicated regardless of which forend I use (ie. New one or the Oem). The problem may have just arisen now out of coincidence.

I don't see any crud buildup or obvious bad wear patterns. I am not really sure where to go next- if I rack the pump quite hard it seems to feed most of the time. should I perhaps see if I can borrow another 870 owners stock metal to see if switching that part would fix the problem? Otherwise where do you buy new shell stop arms?
 
The parts shouldn't be too hard to find. Local gunsmiths, Remington dealers, Brownells etc. If there's no excessive wear then I think a small tweak would be best.
 
OP - you aren't running a sidesaddle that replaces the trigger pins, are you? If so, check the diameter of the trigger pins from the saddle against the original Rem pins - some aftermarket side saddles have incorrect pin diameters that will let your shell latch walk under recoil.
 
enefgee said:
OP - you aren't running a sidesaddle that replaces the trigger pins, are you? If so, check the diameter of the trigger pins from the saddle against the original Rem pins - some aftermarket side saddles have incorrect pin diameters that will let your shell latch walk under recoil.
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Good point!
 
No side saddle (at least not yet) - here is a pic so we know the gun we are rescuing.



This was a 28" waterfowl gun for me for almost a decade without feed issue but I wonder if something has just worn out a bit on it. It has not been used much as of late.

Maybe try new forestock metal and mag spring to rule those out first? I might try to see if I can borrow those parts from someone local.
 
It's very unlikely the forestock metal is worn out. If you remove the stock, check that the arms are parallel to each other and not bowed inward. IF they are parallel, it should work.

Do you have the original follower and spring installed? If so, then you may wish to try a good aftermarket follower and spring. S&J Hardware is a trusted source for many CGN'ers.

If none of that works, you may need to visit a gunsmith.

By the way, is that front sight low enough for that peep? Looks too high.
 
Nice looking shotgun!


platnumbob said:
No side saddle (at least not yet) - here is a pic so we know the gun we are rescuing.



This was a 28" waterfowl gun for me for almost a decade without feed issue but I wonder if something has just worn out a bit on it. It has not been used much as of late.

Maybe try new forestock metal and mag spring to rule those out first? I might try to see if I can borrow those parts from someone local.
Click to expand...
 
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