View Full Version : 870 "Jam" - gun defect or feature?

October 6, 2001, 09:41 PM
Was out with a friend trying out his new 870 Marine Magnum.

Nice gun.

Bit of a problem - sometimes, the gun would jam just after firing, that is, we would get into a situation where we were racking the slide back; but it would only move a fraction of an inch back, and sometimes have to be wiggled back and forth to open. This was not a stuck shell (Walmart special 7 1/2s), it was real metal on metal stoppage.

Eventually, we found that this was happening when we had rearward pressure on the slide, i.e. from using left hand to push the gun into shoulder.

I'm not sure if this is what caused the problem; but we ended up doing an experiment with the gun, and in comparison to an available Mossberg and a Win 1300. Holding the buttstock against my waist, pulling back the slide hard (but with the gun cocked), pulling the trigger, and holding the trigger down hard. On the other 2 shotguns, the slide would move back the instant the hammer fell, even with the trigger down. The 870 would jam up, until we removed finger from trigger and wiggled the slide back and forth a bit.

Is this normal behavior for the 870, and is our technique just incompatible? Or is there something wrong with the gun?


8200 rpm
October 6, 2001, 11:42 PM
My 870 "Terrestrial" Magnum used to do the same thing the first time I took it skeet shooting.

The second time I took it out, I can't remember it doing that. But then again, I might have just subconsciously adjusted my technique to suit the gun. I can't really recall.

Maybe your friends will clear up also.

October 7, 2001, 03:25 AM
I've got a marine magnum and I've never had any problem like you described. Does that one you tried have a side saddle shell carrier on the side? If so maybe the allen screws are too tight and causing the action to get tough.

October 7, 2001, 09:04 AM
Ineresting post. I have an Express Magnum that does this once in a while to a friend of mine. When I shoot it, it never has a problem but when he shoots, it occasionally behaves this way.
I will have to do your test and perhaps suggest that he try alter his technique a bit.

October 7, 2001, 11:02 AM
jadams951 : Gun is bone stock and unaltered.

9mmMike :

Yes, it seemed definitely technique-related - another guy sharing the range could not make it happen, even after we told him to pull back on the forestock while firing, because it was so foreign to him to do so. He would always fire, stop, cycle (even though this was done quickly).


Dave McC
October 7, 2001, 12:06 PM
IMO, the key words here are "New" and "Operator". Try using the strong hand to pull the butt into the pocket, and see if the prob alleviates.

A breakin period will help also, the perts will work polish and the operator will automatically adjust his/her stroke at the same time.

Also, place one drop of CLP on the action bars right where they enter the receiver, and pump a few times. This may help....

October 7, 2001, 12:30 PM
Dave Mcc:

The lube advice is always good for the longevity of the gun, and breakin good for the action.

And a stronghand pull in DID alleviate it.

However, the "jam" was pure metal on metal. Without letting up, there was no way to rack it without taking pressure off the slide and trying again.

As we don't have another 870 for comparison, is this normal behavior for an 870? Can someone try the test I suggested above? (That is, cock the gun, pull slide down hard while pulliing trigger, do not let up on force, keep trigger down - does slide move automatically? i.e. if you have rearward force on the slide, when it breaks it should jump back).


Yes, operating the gun differently would change it; but I don't see this as a desirable feature on a gun that could be used under stress, in a panic where maybe the user applies pressure to rack just BEFORE the trigger breaks, tying up the gun.

Since the 870 has been used as the model of a pump fighting shotgun, I wondered if this is by design, or something broken on this new 870?


October 7, 2001, 01:37 PM
I have a new 870 whick I just shot for the first time Friday. Did not have any problems as you describe. Sounds like a broken gun or you are doing something you shouldn't.

Dave McC
October 7, 2001, 02:18 PM
Just to be sure, I went and grabbed Frankenstein, MADE SURE IT WAS EMPTY, and tried that. Pulling hard on the forearm and pressing the trigger did not cause any prob, the forearm slid back like it's s'posed to.

I doubt your 870 is broken.I'm inclined to still think a bit of use may fix the glitch.

I do think that this is non typical, and should be dealt with under the warranty.

After the warranty center deals with it, please post something here, I'd like to know the answer. Thanks...

October 7, 2001, 02:44 PM
Mossberg pumps, especially when new, do the same thing...

October 7, 2001, 03:38 PM
OK. I just tested my 870. MAKING SURE THE CHAMBER IS EMPTY I can put a wee bit of pressure on the forearm and pull the trigger and hold. The forearm does NOT come back until I release some pressure. Then it slides back. Holding the trigger back does not seem to matter though. I can do this if I release the trigger as well.
I'm not applying much pressure and I only need to ease off a small amount before the slide becomes "unlocked".
I can do this every time. Is the same thing that you are describing? I would bet it is a sharp edge on something inside the receiver.
When this happens to my buddy, we are shooting and there is an unejected shell in there. Moving the forearm back and forth slightly, clears this.
Like I said though, it does not happen to me while shooting so I am not too upset about it.

October 7, 2001, 03:50 PM

Yes that's exactly the problem. I went to Academy today and tried a 870 as well as a Mossberg pump and they both behaved the same way. A little bit of back pressure on the pump while firing would cause the slide to lock until pressure was released.

I really hope that this isn't a 'design' feature because in a panic situation it could be deadly. The Win 1300 does not appear to do this which would make it a lot more appealing.

Can anyone confirm whether or not this is a design feature? If it is, I would guess that it might be a safety thing to make sure that the bolt doesn't open while the cartridge is firing.


October 7, 2001, 09:31 PM
On ALL pump shotguns, there must be metal-to-metal contact between working parts in the pump release device. Some guns have a better/different design that releases easier, and many guns are just well broken it, making the release easy.
Take most any pump gun and pull back FIRMLY as you pull the trigger and the release won't release until you back off on the pressure.
The Remington's release is the rear edge of the left action bar engaging the front of the lock bar on the trigger group. Push up on the shell lifter and look inside the left receiver. As you pull the trigger, the lock bar drops, unless you are pulling back on the pump handle. Sometimes these engagement areas are rough, or dry. You can polish the action bar end or the release on the trigger plate, SLIGHTLY. Don't remove much metal or change the angle on either part. Put a dab of grease on the engagement areas.
Shooting will also smooth it up. However, pull back hard and it won't drop. Unless you gun is just factory-defective, this is normal.

October 8, 2001, 11:55 PM
Thanks for the info, a good cleaning has 'fixed' the 'problem'.

Hopefully I didn't do any permanent damage to the 870 because it was really dry inside. The top of the receiver where the locking block retainer(?) touches has an indentation that looks like a lot of wear for only 20 shots through the gun. Maybe it's normal for an 870?



Dave McC
October 9, 2001, 06:40 AM
Jack, the 870's lockup is accomplished by the bbl extension and the bolt. Is that what you're talking about?

I strip and detail clean the receiver every 1000 rounds or 6 months, whichever's soonest. A very light lube followed by a wipe off over all the inside surfaces is a good idea. Don't dissassemble the trigger group or bolt unless you're:

A, absolutely sure you can get it back together.


B, willing to slink into a gun shop with a box of parts and ask someone that knows to put it all together for you.

Been there, done that....

October 9, 2001, 11:07 AM
If I look at the top of the receiver with the bolt back, I can see one particular dent/line that looks like a lot of wear (but it still probably fine) for 20 or shots. It looks like it was caused by the top of the bolt (by the 'nub' that sticks up). Anyway, it's probably fine, after all it would take a hell of a lot of wear to make this shotgun not work.

Thanks for the info,


October 9, 2001, 04:34 PM
That little notch in the receiver is suppose to be there, that is where the locking block assembly fits in after the bolt closes and locks in with the barrel extension like Dave mentioned.

If you don't have a manual call Remington for one cause you may need it to assist you in stripping it down if not you can always pack it up and take to a gunsmith like Dave metioned.
OTOH when I got my Express a year ago I took it apart and could not reassemble it till I read the assembly instructions
in the manual. Its simple as soon as you learn how to do it.

October 9, 2001, 05:59 PM
That's interesting because the indent/lip didn't look deliberate enough to be there on purpose (although I believe you), and the manual doesn't go into that kind of detail. I'll take another look.

Took the gun apart last night which was easy. The Rem manual is funny because it warns you to lubricate the gun but then doesn't tell you specifically where to lubricate so I'm just lubing the parts that look like they would rub in normal operation.



October 9, 2001, 09:10 PM
Battler You might want to check out this site, it gives some excellent advice on stripping, cleaning, maintaining and "tuning" your 870.


Geoff Ross

October 9, 2001, 09:26 PM
Batler You might want to check out this site, it gives some excellent advice on stripping, cleaning, maintaining and "tuning" yur 870.


Geoff Ross

October 10, 2001, 12:37 AM
If I understand you correctly, you're talking about the small area of wear just behind the barrel extension, in the top of the receiver. This looks like a dent between the barrel and the receiver.
This is caused by the "nub" (which is the bolt locking lug), bumping the ledge of the receiver. This happens because the barrel extension doesn't mate perfectly with the cut in the top of the receiver, and the locking block will just catch the edge as it retracts. This makes the small dent on the receiver.
This is normal, and causes no harm.

October 11, 2001, 02:03 PM
Just checked my Marine Magnum, didn't have your problem.

October 11, 2001, 07:50 PM
I had a 20ga Youth Express that would do the same thing. If you dry fired it and cycled the action--no problem. If you actually fired a shell it would hang up---the problem was with the bolt block and barrel extention. Only way to open it was to jiggle it after the pressure from the shot went down. I took it apart cleaned and lubed----was no help. And NO---this is not normal.
The 20ga. was traded off for a PSE bow.

I currently have an Express 12ga. and had a 12ga. Wingmaster---both were/are slicker than snot.

I would send it back to Remington.

October 16, 2001, 11:36 AM
I have owned around a half a dozen 870s. The only time I had a jam problem was when I added a mag extender.

October 16, 2001, 12:24 PM
Had a similar problem with a new 870 express. Took it out brand new and popped a quail, and it acted like it was frozen. Waited a few minutes and the slide acted normally. Found out it was a bunch of really big burrs in the locking recess on the barrel extension. Took them out with a deburring knife and swiss file, making sure I did not round anything off, and it works correctly now. In my case, I think the burrs on the extension were causing the bolt to seize in the locked position

old hawk
October 18, 2001, 01:20 PM
well thank you for mentiong my 870 site gentlemen,im glad to see it gets use still,altho i have it on another server at :
the main page is http://www.100megspop3.com/oldvalkyry/index.html with about 9-10 other gunny pages i put up as well.what i think the problem is here is flash on the release thats causing his binding up as it stands.what i suggest is taking it apart,clean up the rails on the slide and then the channels in the reciever as well as looking at the tabs that release the stops too for burrs.also look at the disconnector and do the same for it making sure no very sharp flash on the corners etc,i use a small piece or 320 grit emery and then a 600 grit stone to smooth things out on all mine.my new 870- express mag felt like i was fighting it till i straightened the rails ,de-flashed the rails and grooves and generally cleaned up everything,its now smooth as silk and very fast to operate,i just tried this situation with using live fire exercise and snap caps and cant get it to do as you mentioned above in your post but i do believe with some clean up detail work your 870 should be just fine.ALSO!~!!! plkease under no circumstance over tighten the magazine cap screw holding the barrel in!! this WILL gove you this situation however !
what to do is screw the cap down untill she stops klicking easily then one more klik and thats it!
with an overly tightened barrel yes this can happen.if you need help please feel free to email me at [email protected] will be home alot now as my wife is having very serious surgery for a tumor removal so my hunting time is shot and now devoted to her but i will be reading the posts and mail more often.let me know how you make out please.Lars Hawk.its good to see you all again.

Dave McC
October 19, 2001, 06:05 AM
Good to see you too, Hawk. You and your wife are on the prayer list, effective immediately. Hang in there...

October 20, 2001, 01:37 PM
The exact same thing happened to me on the second time out with a new 870 marine magnum pump. The first time I didn't have any problems. I fired a few birdshot rounds and then remington brand OO buck 25 rounds. No problems.

Today I fired 47 rounds of the walmart special 7 1/2. No prooblems. Then I switched to remington OO buck. After a couple of rounds it started happening. I couldn't open the breech after I fired a round. The slide would just not come back. I did the same as Battler and just continued to try to get it to work. After a minute the breech opened. I fired several more rounds and it happened every time. I switched to Federal OO buck ammo. Same thing on the very first round. When I went back to the Walmart bird shot no problems on my last 3 rounds.

After the first time out I didn't clean the 870. Just sprayed some wd40 into the receiver. Iam going to break it down today and clean and lub the receiver and ss if that helps.

I will post my results.


October 23, 2001, 11:53 AM
PROBLEM SOLVED. Even after fieldstriping and lubing the 870 marine I still had the problem of not being able to extract the spent shell casing. I thought the problem was in the receiver.

But on my last round that would'nt extract I could'nt get it out even after waiting and jiggling for several minutes.

So I used a cleaning rod through the barrel to move the casing. Than I realized that the problem was in the end of the barrel near the breach. What happened is that on the heavy loads the brass expanded and got stuck. I guess it would finally realease after it cooled a little. I took the spent casing and put it on another slide action. No problem with extraction. I put it back in the marine mag and it got stuck again. I did this several times.

I found some roughness in the throat of the barrel. Don't know if the roughness was fouling or something else, a bore brush would'nt remove it. I took very fine wet/dry sand paper and used my index finger to polish up the rough spot until smooth. Took some skin off my index finger too ouch.

Went back to the range and I fed it Federal walmart special bird shot, federal tactical OO buck, and Remington OO buck magnum. Worked perfectly.


Dave McC
October 24, 2001, 05:17 AM
Glad to hear it's fixed, Cal.

You might want to try a bit of 4/0 steel wool wrapped around a dowel and chucked up into a variable speed drill.Insert into the chamber end, keep the revs low and polish/clean the whole chamber and bore. Great for plastic buildup and grunge.FWIW, I picked up this time saver right here on this BB.Old dog, new trick...

Sergey Podgirin
October 24, 2001, 08:53 AM
I had such a problem with my Remington 870 Express Magnum. I've rounded and polished the rear edge of the left action bar and now it works OK, almost as soft as Winchester 1300 (imho this pump has the softest action). If someone would try to fit the bar's edge, i'd like to warn You to do it very accurately: it seems that it is very simply to spoil it and it can cause the gun's inability to shot. Conserning me, I decided to round this edge only after I'd purchaised a backup forend assembly.
Now after I've worked with the left action bar, I can pull the forend gently, press the trigger, and an empty shell extracts right after each shot, just like in a semiauto. This weekend I've fired about two hundred 3'' Magnums with my 870 and I've noticed an interesting fact: if I don't touch the forend during the shot with my left hand, the slide opens and extracts an empty shell. This works only with 3''Magnums; when I use 2 3/4" standard ammo the slide does not fully open.

Best regards,
Sergey Podgirin

November 6, 2001, 12:16 PM
So, I've taken my 870 Marine into the shop to let the pros figure out the problem (it's under warranty). According to the guy who works there, they've seen the same kind of problem with the express model but not with the marine. Frankly, I'm kind of pissed that a $400+ shotgun doesn't work correctly out of the box.

The problem is not related to the expanded brass/steel 'sticking' in the chamber, it is definitely an action problem.


November 6, 2001, 03:51 PM
My "first new" Express has over 1000 shells through it now (how come nobody told me how much fun these things are?) and it exhibits none of those symptoms.
It used to do the "apply a little pressure and the slide stayed stuck" but now it is smooth as can be.
I did use old hawk's page and "smoooooth" the action bars.
Now I have to work on my "second new" Express! Yeehaa!
It is way too long between Saturdays (when I can hunt the elusive clay). ;)

November 6, 2001, 04:00 PM
Yeah, that's another thing I've considered...that just breaking the thing in might fix the problem, but since it's under warranty I'll let them have a crack at it first.


old hawk
November 6, 2001, 09:42 PM
ya know im really begining to think of 1 thing here on the express mags such as my black matte one,one is some of these may be very tightly chambered.inoticed one occasion where i had made some loads of 19 gr unique and 1 1/8 oz of 8 shot in a winchester trap xx shell for birds.(incidentally my favorite qauil and grouse load) and she stuck tite on me so bad i had to litteraly use both hands to get the shell out of the chamber.this also happened to me with these same loads on my model 11 and 58 remingtons as well so i called it a bad reloader sizer ring and left it at that (or maybe that charge is justtoo hot but nonetheless).now when i look down the bore of my exp.mag.,i noticed its not very smooth finished in the bore as my other 2 rems are.maybe a production run lot have had tite chambers i am thinking now.what i plan on now doing is polishing the bore up with a swab dosed in jb or rem bore cleaner a few hundred times to **polish** things up some in high hopes of relieving the problem,when a shell is fired it should slip just a micro amount to the breechface,instead sheis being mated to the chamber and the rough finish on the bore's chamber walls is holding the shell tite upon initial firing,the coarseness of the wall will in effect hold it tite untill the shell cools enough to release it at times.if the bore cleaner doesnt solve it a smaller ga. mop wrapped with 600 grit emery wet or dry will do the polish trick and remove the coarseness on a drill at about 500 rpm and only a minute at a time going very slowly the length of the bore and back,i do this with a bore full of oil and the muzzle capped with a cork to polish out old shotgun bores that are badly pitted and have had excellent results in saving some barrels.i will recreate the load when i can get some powder and shot in a month and see what happens then after i do the polish trick on my 870.the one thing i didnt like were the imprfections in my bore being a bit on the rough side almost looking like pits?i dunno.at least i am going to try this.now the other thing i thought of that plagued me years ago with an ithaca 37 and this situation was bad headspacing.yes a whole newer animal and i dont have a 12 ga no go /go gauge either.i will check some shells for reloading on my bench i shot the other day and see if the tell-tale ring on the shells bottom next to the shell rim is bulged out a bit and that will at least give me an idea of what im against here.in meantime im still wracking my brain on this problem,till then,Lars Hawk.

November 7, 2001, 01:45 AM
My first-ever firearm, bought a 870 Express Magnum this 24 October and had the same problem. Being a newbie, I thought it was procedural (I bought a pump for its mechanical reliability).

Shot 75 shells of 8 shot; symptom was intermittent. (Hit my first 4 clays, but my accuracy went downhill from there B^| - I'm hooked now! Also joined the NRA immediately.)

Last weekend, went through 25 shells; no symptom. After my first experience, I guessed it had been jamming because I was "pulling" pressure on the fore-end when firing. I purposely, then, kept my fore-end neutral or pushing out last weekend and had no jams.

BUT - after devouring this thread here on Firing Line, and being new to guns, I think I'll let a gunsmith take a look at it, especially as it's still under warrenty.

Of course, that means being WITHOUT MY SHOTGUN for a time!!!

November 7, 2001, 01:13 PM
Yes, have someone check it out. Our 870s should not jam up from applying fore-end pressure, you can learn to rattle the action forward after each shot to 'free' the action, but that is BS in my opinion.

OldHawk, in my case at least the problem definitely is not related to the shell getting 'stuck' in a tight/unpolished chamber. I can get the gun to jam reliably without a shell in the chamber.

I'll write here if/when my gunsmith figures out what's wrong. (He definitely felt something was wrong when he tried and verified the problem.)


old hawk
November 7, 2001, 01:49 PM
ok i have just recreated the instance by holding the slide very tite to the rear upon firingwith live and no ammo at the range.all i can say is hold the slide tite but just dont pull rearwards while firing.i polished the disconnect faces on the pump rail and itself deflashing it in hopes of relieving the problem,no go but it feels smoother to use the disconnect button on the trigger group.in my opinion there is no fix for that prob other than holding tite yes but not to the rear of the reciever,if you hold tite the disconnect cant travel downwards to unlock the slides rails to go back.now as far as the stuck shells with new ammo i would polish that chamber up some and see what happens then.on one friends new exp. mag that did happen ,then i polished his up for him and no more sticky shells or wiggling to free them to extract.best of luck.Lars

November 7, 2001, 02:03 PM

I hope that's not the final answer - just don't pull back on the fore-end grip - because frankly, that would cause me to reconsider owning an 870.

If you want to rapid fire, for whatever reason, you have to hang onto the gun and saying that any pulling back on the fore-end will cause the gun to 'jam' is just plain bad. Or what if you are in a panick situation, just don't pull back or it will jam? My friends Mossy doesn't have this 'problem'.


old hawk
November 7, 2001, 02:16 PM
jack i wish i had a better answer for your problem bud,i have shot my 870 rapid fire many times in the field grouse hunting and sometimes at the range just doing drills with slugs and pumpkin ball,i just hold the forearm and pump,i dont have much strength in the left arm from a stroke and a lot of stainless steel bars running wrist to elbow in it so pulling back that hard on mine doing the recreation was good and hard on me.other than that all i can suggest is dont pull hard so it can unlock normally,due to the design of this shotgun i just cant see any more modifications being done on its disconnect other than a polish job on the faces to smooth it out more.the best i can say is change the method you use in your hold and speed will come in using it,i wouldnt get rid of the shotgun tho.even my older ithaca will lock like that if i hold her tite up like that,just suggestions my friend.