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GSO-Geko

Marui M870 Fix and Tuning Thread

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I've got a breacher. Take down is practically Identical except for the pistol grip/stock difference. The pump grip is obviously shorter and the mechanism is also shorter slightly. Internally from what we could see its practically identical. Only change we found was that the loading arm now has a metal pin through the plastic arm rather than a plastic pin with metal tips.

 

Also got my breacher firing back on 6 shot. That selector switch spring had unseated! 

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I've got a breacher. Take down is practically Identical except for the pistol grip/stock difference. The pump grip is obviously shorter and the mechanism is also shorter slightly. Internally from what we could see its practically identical. Only change we found was that the loading arm now has a metal pin through the plastic arm rather than a plastic pin with metal tips.

 

Also got my breacher firing back on 6 shot. That selector switch spring had unseated! 

So the metal pin should help then, do you recommend buying the nebula loading arm as a back up?

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Well where mine broke was the plastic pin had bent slightly and the metal tip had sheered off. Now as it's a complete metal pin I would assume that unless you jam it and force rack the pump you'll be fine.

 

I bought the Pro Arms CNC loading arm and ended up having the new reinforced pin in the tactical that I'm selling and putting the Pro Arms in my breacher cause it cost a bomb so thought I might as well! I assume it'll be stronger but how much stronger I've no idea! 

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My apologies if this has been answered before in a previous thread but does anyone know if the two receiver pins near the trigger would match up with the real m870?

 

In other words, would accessories for the real m870 be able to mount on the marui?

 

Thanks

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Can't get my tactical to fire six rounds.  Took it apart, the selector spring seems to weak.  Even when properly seated (as best I can tell from the pictures provided), the spring fails to hold the selector in the correct place when the slider is on six shot.

Very annoying.  

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Can't get my tactical to fire six rounds.  Took it apart, the selector spring seems to weak.  Even when properly seated (as best I can tell from the pictures provided), the spring fails to hold the selector in the correct place when the slider is on six shot.

 

Very annoying.  

 

Mine does that too.. anyone got a fix?

 

I have experimented with mine a bunch, tried shimming the selector up and down, replacing the spring, etc.  I even have the Pro Arms Aluminum Nozzle set and Loading Arm.  Nothing fixes this issue.  But rest assured, if I do manage to figure it out or (more likely) someone else does, I will post it here ASAP, as I would hope anyone else would too.

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Dare I ask how you got the stock pump grip off the arms?  I just brought home a new magpul pump, but can't see the obvious way to get the stock pump off the arm assembly.

 

 

 

Edit*

Nevermind...  Figured it out.  The wrench Magpul included was quite helpful.

Edited by Jonesy

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http://shop.ehobbyasia.com/blackcat-replacement-spring-set-for-marui-m870-shotgun-mechanical-box.html#.VEbtfPnF98E

 

Replaced the feed arm springs with those from this set, 3 and 6 shot now work.

 

Replacement springs in both of the Blackcat sets are much stiffer than the originals.  Set pictured replaces all the springs inside the frame.  Alternate set replaces all the springs between the frame and the body.

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Neat.  I ordered a set of these springs weeks back, and never took them out of the envelope when they arrived.  I just ordered a SAT steel arm from redwolf, so when that arrives I guess I'll install them all in one shot.

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The arm has arrived, and the shotgun is disassembled.  Unfortunately, when I pulled the plastic half of the "gearbox" open the spring loaded components inside for the loading arm, and I think the gate switch became unseated, and I'm not entirely sure on how it all goes back together.  

I can't seem to find a video or schematic detailing that area.  Anyone have resources on that area?

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Figured it out.  Racking seems a lot more stiff than it was before, and it seems to only fire two rounds on three shot, and five on six shot.

Still an improvement over none, and 1-2, in respective modes.

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I love my breacher but it's kinda an odd bird.

While everyone is having problems with the 6 shot mode, I have troubles with the 3 shot mode. It wont work at all.

It will always fire 6bbs.

Any experience with it?

 

I opened it, did the hamer upgrade and checked the other parts but couldn't find what was wrong.

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Hey guys, I'm wondering if you can help. My Breacher gas tanks are spewing gas out the bottom of the tanks, likely from the latch which holds the gas tank in the grip - I've been using Green gas in this thing, ay advice on fixing them? Am I looking at tank swelling and therefore some gaps due to deformation opening up on the tank cos if so I'm going to bin these and get an angrygun stock tank.

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Reading this thread I get the impression this shotgun breaks down a lot. Is that an accurate impression? Makes me worried about getting one.

 

 

Sent from my iPad using Tapatalk

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Mine hasn't broken down at all.. I only opened it up to swap the forerip and stock.

 

It's like any other product; the folks who have problems complain long and loud, and the folks who don't just tend to get on with their lives.

 

I think the most important thing is to be carefull when you load and shoot. If you have a missfeed or other issue make sure you clear it before continuing to rack it.

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