[Puncha]

Took my pump action shotgun out for practice today and ran 55 buckshot shells and 25 high velocity BB shotshells through it. Here's what I noticed.....

When I was fresh, I shot the BB shotshells first. I noticed that after firing and ejecting the 1st shell of the magazine, I squeezed the trigger and all I noticed was the hammer hitting the firing pin and NO BANG. Additionally, the forend could not be retracted. When I push the forend slightly forward and retracted it to examine the chamber, I noticed that a round had not been chambered even though I had clearly extracted the previous fired shell. Completing the cycling motion allowed me to continue shooting and I finished the magazine without issue.

When I shoot pump actions, I normally allow the recoil to aid my shucking motions and it usually isn't a problem. However, with the BB loads today, the problem mentioned in the above paragraph happened every 6 rounds. :cuss: And ALWAYS on the second shotshell.

As I grew tired and moved on to the 00 buckshot, the problem magnified itself. Here is what happenned:

1)load shells
2)rack shotgun
3)Fire shotgun and rack forend to eject shell/load new round.
4)Pull trigger, audible click with NO BOOM. :cuss: :fire:
5)Attempt to rack slide again.
6)Pull trigger, shotshell fires and rack forend to eject shell/load new round.
7)Repeat step 4 with loud cussing, vulgarities and swearing. :mad: :fire:

In other words, when other shooters fire 2 shotshells, I only get to fire one. I'm getting concerned that in a HD scenario, I will be a lot less effective with my gun than I should be.

Any suggestions on how to rectify the above problem? With good ammo and a good shotgun, how can i GUARANTEE 6 complete shucks and 6 shotshell detonations? :confused:

[Third_Rail]

BA/UU/R is the best advice I can give. When I first started using my Mossberg 500A, I was short stroking constantly. It took about an hour at the range to figure out how to cycle it properly and consistantly.

One last word of advice.... work that action HARD. You're not going to hurt anything, and it WILL cure the problem.

[Puncha]

Someone once said, "Train as you intend to fight." Hence, I believe in training using the same load as I intend to use if TSHTF. However, with the lack of reduced recoil buckshot and the nasty kick that Winchester's Super - X XB1200 9pellet 00 buck generates, is it possible that this load is contributing to short shucking? Does fatigue also play a part?

Can someone recommend a training load that replicates 90% of the recoil of a regular buckshot load so that I can practice to eliminate short shucking?

[mnrivrat]

First I would do a little more checking before I assumed the gun was being short stroked.

Happening on the second round of each magazine re-fill could mean that your shell stop needs adjustment. Try loading only two or three shells into the magazine and see if you still have the problem. If the problem goes away, there may be a need for shell stop adjustment, or something other than short chucking.

6 rounds total - does that mean 5 in the magazine and then dropping one into the chamber ? If so, try loading 5 in the magazine and cycling to chamber a round, then re-fill the magazine with that 6th round.

[Fred Fuller]

A few diagnostic questions:

Which make/model is your pumpgun?

Are you using a magazine extension? If so, is it factory or aftermarket?

How old is your magazine spring? What magazine follower are you using? How long since you cleaned the inside of your magazine?

Have you let anyone else shoot your gun and does it do this when another person shoots it?

If you fire a shot, then wait for a 1-count, then pump the gun, will it feed/chamber a round under those conditions?

Your problem could have any one or more of several several causes, just trying to sort out what's going on with your gun from a few thousand miles away- thus the questions.

More later,

lpl/nc

[Puncha]

To Lee Lapin,

Q:Which make/model is your pumpgun?

A:Remington Model 870 marine magnum. The gun is new, bought last month. As of today I have fired 325 turkeyshot shells and 90 buckshot shells.

Q:Are you using a magazine extension? If so, is it factory or aftermarket?

A:The magazine extention came with the gun as a factory standard part.

Q:How old is your magazine spring? What magazine follower are you using? How long since you cleaned the inside of your magazine?

A:Magazine spring is brand new. Magazine follower? If that is the lever gate thing that I have to depress before I load shells then it is also a standard part of the shotgun. I clean my shotgun like some guy afflicted with OCD - in detail after every shoot. The insides of the magazine were cleaned last week and passed inspection by a former army sergeant major that I shoot with occasionally.

Q:Have you let anyone else shoot your gun and does it do this when another person shoots it?

A:No. The last person that I allowed to handle my personal firearm damaged it thorugh mishandling.

Q:If you fire a shot, then wait for a 1-count, then pump the gun, will it feed/chamber a round under those conditions?

A:I have not tried that. I usually use the recoil to initiate cycling as I feel that it cuts down on the cheek slapping punishment. I have tried to conciously pump the gun harder to avoid shortshucking but as I get tired and my cheekbone area bruises, the "failures to fire become VERY COMMON. :fire:

Mr Lapin, if I may clarify.....

are you asking me to fire a shot, rack the forend back....wait 1 second...and then rack the forend forward? Won't that result in a mis-feed or jam? I thought that the slide had to be IMMEDIATELY shucked after each shot.

[HSMITH]

Rack the slide like you intend to break the gun, HARD back and HARD forward. CLACK CLACK!!!!!!!

You won't hurt it, and if the gun is right mechanically your problems will disappear.

[Fred Fuller]

Mr Lapin, if I may clarify.....

are you asking me to fire a shot, rack the forend back....wait 1 second...and then rack the forend forward? Won't that result in a mis-feed or jam? I thought that the slide had to be IMMEDIATELY shucked after each shot.
==========================

What I'd like for you to try is to fire the shot, then wait for a second before you run the bolt/shuck the slide or however you want to phrase it. The gun shouldn't misfeed or jam even if you wait a half hour or all day before you shuck it after firing, but waiting that much time is a little excessive for the purposes of the question 8^).

What I am trying to determine is whether the problem is a hardware issue or if it's operator induced. In a new 870MM that has been field stripped and properly cleaned and lubricated, there shouldn't be mechanical issues causing the problem. Note I said _shouldn't be_, it can't be ruled out- that's the main purpose of the shoot and wait a bit before shucking experiment.

Oh, and the follower is the part at the end of the magazine spring that appears at the loading port end of the magazine when the gun is empty. On current production 870s it's plastic, shaped like a cup to hold the end of the coil magazine spring, and might be gray, black or orange in color.

If the gun runs properly when being fired just a bit slower, or when being fired by another shooter, that might tell us something about the problem. Of course, then we have to figure out WHAT it tells us. But if the gun won't run properly when fired at a bit slower cyclic rate, that should indicate a mechanical problem. I don't feel comfortable hazarding a guess as to what's happening without knowing those answers.

No matter what else, make sure you bring the slide briskly and firmly ALL THE WAY to the rear when you run the bolt. It's possible to eject an empty and not feed a live round out of the magazine by shortstroking, it isn't usual and it isn't usually repeatable but it does happen.

Also check to make sure nothing is interfering with or blocking the forearm in its travel to the rear, that the top of the forearm isn't rubbing against the bottom of the barrel where it is out of sight, for example. I have seen one 870 with synthetic furniture where the forearm made contact with the bottom of the barrel and interfered with the complete opening of the bolt. Look at the top of the forearm with the barrel removed to see if there is any evidence of contact with the barrel. I doubt it's likely in your case but i have seen it happen- removing some material from the top of the forearm was necessary to allow that particular gun to function properly. It's just one more thing to consider and rule out.

All this would be so much easier if i could just get hands on the gun... 8^).

One more thing- there's no real need to beat yourself up with heavy loads in practice. Find yourself something less punishing (and likely less expensive too) to practice with. If you have to use heavy loads in real life, your adrenalin level will more than compensate. Meanwhile it's a lot easier on you to work out with lighter loads for most of your practice time. Note that you should definitely shoot enough of whatever you choose for defensive loads to make sure they will run in the gun, even when the gun is hot.

Hope you can get it worked out soon,

lpl/nc/USA

[kirbythegunsmith]

Proper diagnosis involves removing as many variables as possible.
Try with less than a full tube of shells.
Try without the extension in place, with a regulation type magazine cap.
Any tiny mis-alignment of the tube extension or improper seating gives an opportunity for the shell follower to stick, or RIM EDGE of a shell to be temporarily impeded. A dirty mag tube interior or weak spring will have a similar effect, especially with heavy recoil and heavy line of shells. The gun is recoiling back, but the shells try to compress the spring. That is one reason for a heavy-tension spring inside long magazine tubes, to assist in overcoming inertia and tube-wall friction of the extra shells.

There are some low-recoil buckshot loads out there (slugs, too), sometimes called "tactical" loads. Those will probably be sufficient in any WTSHTF event, and give you faster recovery. I just wonder if they also have lower muzzle flash level in low light situations. I'll bet the mag loads have a huge flash bloom at night. I would expect to use sabot loads for more penetration potential due to lower frontal area if I thought that was a need, with maybe being the last shell or 2 to be fired (first inserted). They need to be ones compatible with smooth bore, since you lack rifling. Rifled bores have poor shot load control.

Pumping a gun more than what could be considered "vigorous" is over the top. Just don't be tentative with the pumping. Slamming a gun super-hard is not productive, like slamming a door, and is a sign that something needs fixing if that is the only way a mechanism will function.

See the article that I wrote (attached) to see pictures of shells run through a gun by someone that thought slam-pumping was a way to avoid needed repairs.

kirbythegunsmith@hotmail.com

[Puncha]

I have done more shooting with my new Remington 870 marine magnum and now know more about the problem. The following contains additional details which may aid in diagnosis. If you guys know anything, please chime in.

As I suspected short cycling to be an issue, I loaded my shotgun with 6+1 2 3/4" 7/8oz light 7 1/2# trap loads to practice firing and pumping my shotgun. My approach was to pull the trigger, retract the forend completely, wait 1 second and then pump the forend forward for the next shot. To my complete suprise, all 7 shells fired perfectly without any failure to chamber or extract. I was able to repeat this with 50 shotshells.

Next, I moved on to Winchester's 9 pellet OO buck 2 3/4" magnum load (product code XB1200). With the significant recoil from this load, I found that the gun was only reliable (100% certain chambering of shell after each shot) when 4 shells where loaded in the magazine with an empty chamber.
When 6 shells were loaded, I pumped once, fired, retracted the forend to extract the spent shell and discovered that the 2th shell was STUCK IN THE MAGAZINE TUBE :fire: . I had to pump the gun again to load and fire the 2nd shell. :cuss: As earlier stated, the 3th,4rd, 5th and 6th shells loaded reliably.

Firing an intermediate recoil load (Fiocchi's 2 3/4" 1 1/8oz #4 birdshot load), I noticed that the shotgun was able to reliably load and chamber 5 shells. 6 shells proved unreliable with the 2nd round requiring two pumps to chamber while sometimes, it was the 3rd round that required a double pump.

So....what should I do? Considering that it's a new shotgun with only 580 shells though it so far, should I replace the magazine spring? What can I do to remedy the problem if I do not have access to a gunsmith?

[Fred Fuller]

Puncha,

You still haven't said that you tried what I suggested initially, which was:
1)Shoot
2)WAIT
3)Pump
I'd still like to know if that makes any difference with heavy loads.

You said you tried Shoot-Pump-Wait and that worked with lower recoil loads but not with buckshot or intermediate recoil loads. I suspect the difficulty lies either with the magazine spring or with the fit of the magazine extension, less likely the problem is with the shell latches/action bars but still possibly there is some difficulty there.

My initial thought was that you are pumping the gun so fast after shooting that the magazine spring had not had time to overcome the inertia of the magazine full of shells when the action bar tripped the shell latch to release the next round from the magazine tube. I don't know if that's possible or not, it would seem to be a theoretical possibility if an outside one. The 870 design requires a slight forward movement of the forearm to release the action when it is fired, usually recoil provides that impulse and that should allow enough time for the magazine spring to do its job, I would think.

Since the gun works when not loaded to capacity, I am more suspicious of the fit of the magazine extension at this point... or perhaps some other magazine related problem is the issue.

IF another shooter finds the same problem, or if the problem persists when you shoot-wait-pump, that calls for more speculation...

lpl/nc

[McMurray]

I'm actually having the same problems as Puncha seems to be having, except in a Mossberg 500.

Lapin, I did something like the test you proposed to Puncha. I shoot skeet with the gun. At first I was told that i was short shucking the gun, even though I was almost certain my shucking was complete. When I would step up to the stations, I would load one shell in the chamber, and then put one in the magazine. After shooting the round in the chamber, I would then cycle the action, pull the trigger, and then no bam. The shell would be lying at my feet. to me it seemed as if it were just flying out the bottom.

My suspicions were confirmed the other day when I went shooting with a friend. When he fired my gun, I visibly saw the shell fly out of the bottom of the reciever, before he even went to cycle the action, so it followed your 1. shoot, 2. wait, and 3. pump.

Obvoiusly it shouldn't do this.

I have two theories and would like some input:

1. Magazine spring is too weak (I've only had the gun for about a year, however, the few times i've loaded 5 shells in the magazine i didn't experience the problem)

2.The cartridge stop on the reciever is broken/defective/needs tuning?

any input would be greatly appreciated. If possible, I'd like to fix it myself, rather than sending the whole thing into mossberg.

[sm]

Lee Lapin, listen to him.

To which I will add...

Ammunition.

Some of this ammunition may not be spec'd correct either. One reason we suggest one run 100 - 200 rds of ammunition through a gun is for reliability check.

Guns that I/we KNEW, the chambers were clean, bone stock (less to worry about a mag extension, too tight side saddle and whatever) and everything has worked flawlessly - developed hic-ups with some of these newer shells out of spec.

Promo loads for practice we new about from the get-go, but some more expensive ammo , reduced recoil ammo and Internet bought whoopie-doo stuff not reliable.

I tossed in some 20+ (?) year old Winchester/Western 9 pellet 00 buck and these guns ran like a Ferrari going full tilt boogie.

Tossed in some 10-12 year old Fed nine pellet 00 buck and slugs...again full tilt boogie.

One reason I personally suggest buy ammunition locally to test a variety, make note of what works for sure, and run back and try to get the same lot numbers on slugs, and center fire handgun and rifle ammo that YOUR gun shoots reliable and best.

If later one wants to get a Internet order for price fine - at least one knows the ammo that does work in a gun.

Some of what we "finally" shot up , was an Internet order that would not run in much of anything.

Then again some guns...like single shot and double barrel shotguns always have and always will have a place in shotgunning - no matter what the need for shotgun a may be.

It makes no difference how hi-tech a gun is, or the ammo, or how many rounds a gun will hold - if the ammo does not run in the gun.

[Snarlingiron]

Maybe I'm oversimplifying, but I haven't seen anyone mention complete disassembly, cleaning, lubricating and re-assembly. My friend and I bought Remington 870 Express shotguns about 2 weeks apart. We both did a complete disassembly, clean, lubricate and reassembly. The guns were filthy, and not well lubricated. The application of some light grease (GW25B) on the heavy wear areas and general lubrication with light oil (I use Mobile 1) did wonders for the smoothness and functionality of the guns. If you haven't done this, you really need to do it anyway. It may help your problem, and if it doesn't what have you lost but a half hour or so? Always start with the basics before moving on to more complicated stuff.

[Puncha]

I went to my dealer yesterday to tell him about my problem. He seemed to be at a loss as to how to remedy or explain my problem about the 1st, 2nd and 3rd shell sticking in the magazine tube and needing two shucks in order to chamber.

As suggested by Lee Lapin, the problem could be with the magazine spring and the fit of the remington factory +2 magazine extention that came with the gun.

When I mentioned this to my dealer, he said to try inspecting the magazine spring by holding it up and letting it hang freely. He said that if the spring does not hang straight but instead bends to one side at any point along its length, I could have a slightly deformed and thus weakened spring. This may result in lesser pushing strength and inability to push a line of 6 heavy shotshells along.

Is this BS or is he right? :confused: I thought that as soon as the spring was depressed within the magazine tube, it would not compress in a perfectly straight line but would bend to one side or the other. In other words, it is perfectly NORMAL for long springs not to hang perfectly straight.

:scrutiny: He also said to try and gently bend the spring back to being straight if there seemed to be slight sideways "deformation". It is safe to try this?

Lastly I bought a Tacstar +2 mag extention with new spring from him. What is Tacstar's quality like? I am thinking of replacing the factory mag extention with the tacstar's as a solution to my woes.

[Fred Fuller]

Strange things happen from time to time that confuse everyone. I saw one brand new 20 ga. Wingmaster, fresh out of the box, that would not allow one particular brand of shotshells into its magazine. Everything else, no problem- but not that brand. Shells of that brand from that lot may have been sized a little bigger, magazine opening may have been at the small end of spec, but getting those shells into that magazine just was not going to happen- the rims would not fit inside.

Puncha, I am sorry to hear your problem persists and your dealer is confused. Perhaps a longer/stronger magazine spring will help, it may be that changing magazine extensions will too. I've never had any trouble with Tacstar extensions, just be sure to get a barrel clamp to go with the 2-round extensions as (IIRC) they don't come with one, and you can't use your original clamp because there is no notch for the screw in the TacStar. Remington extensions are among the best available and it would be a shame to hear an aftermarket extension worked when a factory one didn't. But strange things happen... .

I'd still be curious to see what happened when a standard magazine cap and a 4-shot magazine spring were used in your gun. Do you know anyone with a standard capacity 870 of the same gauge as yours who would let you use those parts from their gun to test fire yours?

McMurray,
Your problem is most likely a worn/bent/broken/mistimed shell latch, assuming the shell is fully inserted into the magazine tube. As new as your gun is it shouldn't be doing this (neither should Puncha's, obviously). I don't think in your case the magazine spring is the culprit.

hth,

lpl/nc

[Bill2k1]

I believe your problem is you're using the recoil to assist in operating the action. I don't mean to sound demeaning but are you sure you are using good form? I never feel my gun kick or get a cheek slap unless I am taking odd angle shots at ducks. I know a guy who often compains of cheek slap and insane kick and he uses poor form when he shoots.

I have had the same problem as you describe. I narrowed it down to holding the gun poorly. It seems when I would take shots at dove and not push the pump forward while holding, I would short stroke it. I am now sure it was because I was afraid of getting my expensive gun messed up. That all went the way of the dodo when I threw it down a gravel driveway. Now the gun gets used the most because I am not afraid of it at all.

Now when I shoot, it seems like time slows for a second when the game is coming in. In a blink of an eye, I know my form is good and that everything is going to function fine, its usually up to me to miss the birds not the gun.

[Puncha]

To Lee Lapin and all your helpful guys,

:fire: I am fast losing hope that this problem will ever be solved. :(

I remember that the last time I shot my 870, I gave it a through clean and even made sure that the factory supplied mag extention was spotless. Anyway, I read this thread,

http://www.thehighroad.org/showthread.php?t=179471

and decided to try some remedial measures. Other than the fact that my shotgun could pass military inspection, I did the following:

1) Replace the factory mag extention with a tacstar extention.
2) Replace the factory mag spring with a tacstar spring.

Result:
NO CHANGE! :cuss: Winchester's 2 3/4" 9 pellet magnum 00 buckshot still only fires reliably when my shotgun is loaded with a 3+1 payload. Otherwise, if 7 shells are loaded, the 6th and 5th will still stick in the magazine tube. At this point, I was so incensed that I needed to stop shooting to cool down.

Later on, I noticed that the factory mag spring was longer than the tacstar spring. Coupled with the fact that the tacstar extention was shorter, I decided to combine the longer factory spring with the shorter tacstar extention. The idea was to increase spring "power". After loading up on various shells, here's what I noticed:

Winchester Buckshot:
6 and 7 shell payloads still showed problems but initally, the 4+1 payload fed reliably for about 2 times. The shotgun then returned to its habit of only accepting 3+1 shells for fast and reliable firing.

Winchester Australia BB high velocity:
Slight improvement from my last range session, my shotgun now fires reliably with a 4+1 payload vs a 3+1 or even 2+1 payload previously.

Fiocchi PL32 1 1/8oz #4 birdshot:
No change from before, it still shoots a 4+1 payload with certainty but has "shell in mag sticking" for the 6th and 5th shell if 6+1 shells are loaded.

I ready to give up trying to solve this problem! :banghead: There are virtually no civilian gunsmiths in my country to turn to and I'm all out of ideas on how to get a 6+1 payload of heavy 2 3/4" magnum 00 buckshot shells to feed with 100% certainty when fired quickly.

Ps: To all you guys who suggested that I fire the shotgun wait 1-2 seconds and then try to shuck the action, this does work. I loaded the gun with 7 shells, fired the 1st shell, shucked after a 2 second delay, loaded the second shell easily and could fire the rest of the 5 shots without any shells sticking in the magazine. HOWEVER, shooting shotguns with the support arm behind the forend (so as not to retract the forend with the recoil) is painful and tiring while shooting the gun with the a pull-push technique (trigger hand pulling the stock in, support hand pushing the forend out) is both tiring and inaccurate. I CANNOT shoot this way for any reasonable length of time.

:barf: It seems that for 100% functionality in my only shotgun, I'm going to have to reply on either 3+1 buckshot shells or 6+1 #7 1/2 birdshot shells for HD.

[Fred Fuller]

Puncha,

Find someone you can trust not to break up your shotgun, and let them try shooting it with the same loads that are giving you trouble. With the gun running OK when you wait for a second or two after firing and before pumping, that sounds like it's a technique problem on your part rather than a mechanical problem. Having the gun run OK for another shooter would help confirm that the problem lies with the operator rather than the gun.

Even with a shotgun, there needs to be proper follow-through on each shot to insure hits- just as with a rifle or pistol. The shooter's job on each shot is not over until the payload completely clears the muzzle. The shooter HAS to maintain control of the grip/sight picture/trigger squeeze all the way through the shot in order to get consistent hits.

Number one issue with shotguns is gun fit. Puncha, I am beginning to believe your gun does not fit you properly, that the stock is too long for you. Do you have access to a shotgun with a shorter stock you could try, to see if it feels better? What stock does your gun have presently, the thin-walled synthetic (black plastic) stock that Remington normally supplies on Marine Magnums? How long (measuring from the front of the trigger straight back to the outside edge of the recoil pad) is the length of pull on your shotgun?

Does your gun still have the field length forearm (9" long IIRC) or does it have the shorter police style forearm (which IIRC is 7" long)? The longer forearm often works better for people who need a shorter stock to shoot comfortably.

Do you feel comfortable with the idea of changing out the stock on your shotgun yourself? All it takes is removing two recoil pad screws (Phillips head screws usually), then taking out the stock bolt (long shank standard or slot head screwdriver usually) to get the old stock off, and replacing it with the new stock. Getting a shorter stock might be a worthwhile thing to do. It's a tough proposition to shorten the thin-wall synthetic stocks, Speedfeed, Hogue and others make 'youth' length stocks that fit 870s that are black synthetic, with LOPs ranging from 12" to 13". If you have trouble finding one, PM me.

When shooting your shotgun, pull the stock back firmly into your shoulder with your shooting hand, and hold the forearm with your support hand. Don't pull back or push forward on the forearm with your support hand, just hold on and direct the muzzle of the gun to the target. I would advise looking for and using reduced recoil buckshot loads at this point, if you have them available to you.

Hope all this helps, I understand your frustration and wish I were close enough to offer better assistance...

lpl/nc

[sm]

Lee , again listen to him - I agree with his posts.

Winchester ammunition - quite a few folks have trouble with it.
Fiochhi, I have never had a problem with Fiocchi, nor has anyone else I know of ( or remember saying so).
Short version - don't use Win, and the "balls" in reduced recoil loads, bounce back!

Someone else shooting your gun is a good idea.

Send gun back to Remington. Call them and ask if they want the FIRED /EMPTY
hulls sent with gun to inspect. Inform them of the exact load, with lot numbers for sure.

IF, IF you have lost faith in this gun. Tell Remington you have. Be very polite, sincere, humble. Just as you would appreciate someone being with you and you having to deal with a Customer Service Complaint.

Let them have the opportunity to save face, make right. You have a right to be upset - just allow Rem to save face and make right. Remember - we have had folks air laundry on Internet, and when a customer service complaint is laundered, when there is un-civil behavior, then the complaint dept is not as willing to deal these folks as those being nice, or trying to be.

[kirbythegunsmith]

I have one more suggestion that anyone can try if they use a magazine extension.
Make a note and mark the rotational spot of the extension when it is tight in the installed position, so that you may compare that position to the tight installed position when the extension is tightened WITHOUT the barrel installed (other guns, like 1100's, same instance without the FOREARM installed). You want the tube extension to have all the room to rotate to the bottom. (Occasionally the threads may not be deep enough or be filled with silver solder etc. to make an artificial bottoming that is NOT the ends of the two tubes butting against each other)There should be a VERY SMALL difference in how much further the extension can rotate. Compare the before and after rotation at the "bottom out" point.
Any large gap between the different "bottoming out" points shows that there is a large gap present between the two pieces of magazine that you are wanting to use. Large gap translates into the rim edge or spring coil having a place to catch.
The other problem that is slightly possible is a misalignment of the centerlines of the two pieces when the extension is threaded in place. There is usually a tiny hole in the end of the extension (for air venting) that you may look through with the internal parts removed and a light source at the receiver end of the tube. Don't use a light so bright that you get large amounts glare. Even a piece of white paper can reflect sufficient light to see if there is a lip of the tube edge showing itself as a shadow on one side.
Off center alignment allows a place to catch. The edge that is sticking out on the direction of feed travel for the shells may be slightly chamfered with a half-round file (very fine) or other careful beveling arrangement. (We are talking the threaded end of the factory magazine tube, by the way)
If there is no misalignment that can be seen through the mag. extension, but a gap is present and has been diagnosed as such, a small chamfer all around the threaded end of the magazine tube will be a possible help. Always start with a small alteration. Yuo can always remove more. Putting the metal back is a lot more expensive.
Remember the old adage about cutting a board twice, and it's still too short?

See the attached pictures of crooked choke tube holes in shotgun barrels in the thread about "analyzing this pattern". Manufacture errors can be present in other parts, too.

kirbythegunsmith@hotmail.com

[Puncha]

Had a brain wave after reading the last few helpful posts from Lee Lapin, Kirby and others.

It seems that heavy recoil is the problem as mild kicking loads feed fine. In other words, once the load exceeds 1oz and the dram equivalent climbs past 3 1/4ozs, shell-sticking-in-mag problems occur.

I've already stated that a 3+1 fullpower buckshot load will work reliably 90% of the time. I decided that rather than face the goblin hordes with a 6+1 load that jammed on the 6th, 5th and 4th shot, how about a 3 shots of 7/8oz #7 1/2 birdshot trap load(light recoil) as the 1st 3 shots and 4 rounds of regular cheekbone jarring 9-pellet 00 buck as the subsequent 4 shots. The idea is that since the 1st 3 shots only fed reliably if they were light kicking, then I would oblidge my shotgun with a suitable target load. As the 3rd shell was light kicking, it should not induce the next shell (relatively heavier buckshot) to stick in the magazine due to inertia. The 4th shell (buckshot) should then load reliably and the 5th, 6th and 7th buckshot rounds should follow without the need for double shucking. :) I really had my fingers crossed that this experiment would work.

Anyhow, here is what happenned:

initially tried loading the 1st 4 shells as light trap loads and the last 3 shells as buckshot. Good reliability achieved and felt comforted that my shotgun could handle a full load with something other than 100% light trap loads.

Felt braver and loaded the 1st 3 shell as light trap and the last 4 rounds as "no nonsence" buckshot. What happenned suprised me....the first 3 shells (light trap) shot and fed fine as expected. The 4th shell (buckshot) fed reliably but the 5th shell showed unpredictability, sometimes, it would load fine but sometimes, it would stick in the magazine tube. The 6th and 7th shells would feed like clockwork as expected.

So what I have is....a NEW :mad: marine magnum 870 shotgun that in the HD role will fire:
1 warning shot
1 shot to send a pain message to the invader to leave
1 shot to reinforce the 1st pain message
1 load of buckshot to hopefully incapacitate the intruder
*Necessary double shuck due to shell sticking + hope threat has been neutralized*
3 panicked blasts of 00 buckshot if the previous 4 shells have not either incapacitated the intruder or convinced him to leave my home.

Lastly, I installed a tacstar barrel clamp onto my tacstar mag extention. After a full 2 magazines of shells, the barrel clamp became very loose and started to migrate to the sighting bead. What can I do to ensure that the clamp stays put?

[gak]

Have you checked for a gap between the extension and the nut that holds it on ? Once you remove the long extension tube, unscrew the nut on the end and screw the nut down first till you click onto the retaining pin, then put in the spring and screw the tube onto the nut. If there is a gap between the two, the spring can get caught in there.

You mentioned when you get tired it screws up more often.

I remember a chap posted that when he'd get tired he'd forget the Push-Pull technique so his shotgun would jam. He would have to consciously remember to PUSH the fore-end away from him as he fires, and PULL the trigger-area grip toward him. If he got tired and forgot to push the fore-end away, the fore-end partially came back under recoil, half-cycling his shotgun and mucking up the feed/locking mechanism.

I tried limp-wristing my 870's after I read that article, and I was able to get a partial feed problem just by allowing the fore-end to come back partially during recoil then move forward again. Sorta like a half-pump.

Try the push-pull, and maybe come back the next day rather then try to diagnose problems when you're too tired.

I have two marine magnums, no problem with six 2 3/4 shells in the mag tube in either, using oem springs but aftermarket brownells aluminum followers (hate plastic). Hopefully an 870 armourer lives near you and can tell you if it's a lost cause and needs to be sent back for repair.