Remington 870 shell surge solution: Mag spring and/or action bar cam position?

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alpining

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Couldn't find a thread on this, please let me know if I've missed it...

Recently discovered (via video) that I'm not short-cycling the action, and the culprit is most likely shell surge. I don't want to simply "slow down" my pump cycle because when I'm shooting on the clock I don't trust myself to successfully do that every time. So, what sort of mechanical fix can I look at?

The most commonly suggested solution to the shell surge problem with the 870 is simply a heavier / longer magazine spring. I've seen a few comments on the interwebs saying that this helps but doesn't eliminate the issue, and that repositioning the cam location on the action bar has given the user a more permanent fix. No details on how to alter the cam position, though.

What advice do you have for me?

Thanks in advance.
 
Without looking into what "shell surge" is, I'm guessing that the shell latches are not being actuated by the action bar cams and not releasing a new round when you are cycling the action quickly...?
I would try a new spring first, as it is easily swapped out and reversible. Modifying the action bars is a more permanent idea and not easily undone if it goes wrong.
 
IIRC shell surge is the forward motion of the cartridges in the mag tube under recoil. My armourer's course advised this can occur. About 1 shooter in a million can actually pump the 870 faster than the shells can be reversed rearward by the mag spring. This results in no cartridge being delivered onto the carrier from the mag. Remington fixed this in the Police Magnum by using an extra strength mag tube spring.

Darryl
 
gunrunner100 said:
Without looking into what "shell surge" is, I'm guessing that the shell latches are not being actuated by the action bar cams and not releasing a new round when you are cycling the action quickly...?
I would try a new spring first, as it is easily swapped out and reversible. Modifying the action bars is a more permanent idea and not easily undone if it goes wrong.
Click to expand...

The symptom is that during quick cycling, I'll sometimes come up with an empty chamber (10-20% of the time). I (and everyone else) really thought I was simply short-cycling the action, but I just had the chance to watch a video of my shooting, and that's definitely not the case.

Close inspection during slow cycling shows that the action bars are working properly with the shell latches. And I've never been able to induce the malfunction using dummy rounds while cycling the heck out of the action. Recoil seems to be the key ingredient, and that led me to think "shell surge".


madtrapper143 said:
IIRC shell surge is the forward motion of the cartridges in the mag tube under recoil. My armourer's course advised this can occur. About 1 shooter in a million can actually pump the 870 faster than the shells can be reversed rearward by the mag spring. This results in no cartridge being delivered onto the carrier from the mag. Remington fixed this in the Police Magnum by using an extra strength mag tube spring.

Darryl
Click to expand...

I think it's gotta be more than 1 in a million - I'm really not that special. And I don't think it's that I'm pumping faster than the spring can sproing: It's that recoil causes the shell stack to shift forward inside the mag tube, and if the timing of the pump cycle is just right you get the malfunction. Deliberate slow cycling will eliminate the problem, but I compete with my 870, so that's not a preferred option.

I also think it probably has a lot to do with how you grip the shotgun and how you ride the recoil: I'm a fairly lightweight guy (~175lbs), so the shotgun probably moves more (and more quickly) on my shoulder during recoil than with some bigger guys.

That, coupled with just the right balance of shell stack mass and perhaps a slightly underpowered magazine spring... It all adds up to shell surge in my case. It would be interesting to play around with lighter and heavier loads to see if I can induce the problem more/less often, but really, I just want a mechanical fix so that I don't have to worry about cycling it "wrong" while under pressure, regardless of ammunition type.

The heavy spring seems like the way to go for now. Though I've heard that some guys still have the issue after replacing the spring, so I was curious about altering the latches and cams.
 
No, not one in a million. It's happened to me too, using several different 870s, and I just took it as a sign I was shooting too fast. Better put, I was trying to shoot too fast. But if it happens to a lot of people shooting the gun in question, it shows there is indeed a fault in the mechanism.
 
Guys this is very RARE. There are about 10,000,000,000 870's out there and only two shooters here have experienced this. I have hunted with, worked with, trained with and repaired 870's for over 40 years and have never had or seen this happen. It is most prevalent with a full magazine of 00 buck or heavier lead loads. But as I said before the mag spring for a police magnum will solve it. Just remember it will be a lot tougher to get shells into the mag once that spring is changed.

Darryl
 
madtrapper143 said:
Guys this is very RARE. There are about 10,000,000,000 870's out there and only two shooters here have experienced this. I have hunted with, worked with, trained with and repaired 870's for over 40 years and have never had or seen this happen. It is most prevalent with a full magazine of 00 buck or heavier lead loads. But as I said before the mag spring for a police magnum will solve it. Just remember it will be a lot tougher to get shells into the mag once that spring is changed.

Darryl
Click to expand...

I don't disagree, Darryl, but I think the reason we don't see it more often is simply because not a lot of 870 shooters are really trying to go fast fast fast. And then not a lot will put the time in to develop their cycle speed. And nor should they - But for my brand of gun games, competing against guys with semiautos, cycle speed is critical. It's not that the shooters who experience the problem are unusual / rare, it's that the shooting conditions in which someone would experience this are fairly rare. I think. Maybe. :)
 
+10% 3 and 5 shot

ht tp://www.brownells.com/shotgun-parts/magazine-tube-parts/magazine-springs/remington-870-extra-power-magazine-spring-prod16499.aspx

+10% 6 and 7 shot

Magazine Tube Spring for Remington 870 - 6 & 7 shot capacity extended tubes improves feeding and reliability. No fitting required. These extended tubes are used on many law enforcement guns. For use in Scattergun conversions as well

ht tp://www.gunsprings.com/Rifles%20%26%20Shotguns/REMINGTON/870,%20878,%2011-48,%20SPT-48,%20SPT-58/cID2/mID108/dID216#606
 
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Never in 40 plus years have I ever heard of something called shell surge. Shot pins and plates for years with guys using every kind of pump gun and not once has shell surge ever ben mentioned or an issue. Shot my own 870 with its mag extension as fast a possible too.
Mind you, few pin/plate shooters ever used buck shot, except maybe the FNG's. If a stronger spring fixes it, it'd be a cheap fix. Always go with the easy solutions first.
 
sunray said:
Never in 40 plus years have I ever heard of something called shell surge. Shot pins and plates for years with guys using every kind of pump gun and not once has shell surge ever ben mentioned or an issue. Shot my own 870 with its mag extension as fast a possible too.
Mind you, few pin/plate shooters ever used buck shot, except maybe the FNG's. If a stronger spring fixes it, it'd be a cheap fix. Always go with the easy solutions first.
Click to expand...

Next time you're out in YYC, drop me a line and I'll be happy to demonstrate it for you. :)

Ammo used was Federal high brass heavy game load 7.5 birdshot. Who the heck can afford to shoot buckshot at targets?!


EDIT: I should add that I'm definitely open to hearing other diagnoses of my problem. It just really really sounds like the "shell surge" issue to me, a term that I learned two days ago from a Remington armorer after describing my malfunction.
 
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Is your spring binding up?
One time my 870 spring twisted on me causing a no feed then an almost a double feed.
 
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