A&K M870 Internals HD PICS

[kojak]

It's not a carry issue, it's just heavier than I'd like.  The potmetal outer receiver seems to be the main culprit, maybe a plastic body will fit over the ACM inner shell.   

 

My first attempt as disassembly/reassembly didn't go too well: a cut down APS2 spring fit perfectly but the trigger feels different (less clicky), theres more resistance in the pump return, and worst of all there's no BB retention (round rolls right out of the barrel).  Guess I'll try again tomorrow.  

[swatti]

Dump the stock-barrel & hopup. Put in a regular AEG-barrel and hopup, its well worth the 30min it takes to mod one in.

 

Edit:

ITS DONE!

 

https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-frc1/r270/883184_665756853464481_2086958718_o.jpg

 

870-Charger gearbox-shell, few parts too. Acm cylinder. Hand-made steel bits. Real-steel speedfeed stock, ATI heatshield & sights, top-mounted rail and custom made steel magazine-tube with new mounting-method. Solid like a rock, weights about the same as RS. 110m/s & R-hop.

 

Godly skirmisher.

[RodrigoMF]

No..

 

They simple don´t shoot..

 

cocking normally, but the bb doesn´t shoot.

 

When i point the muzzle to down the bb drop down the barrel.

[swatti]

The gun still cocks normal?

 

BB falling out is due to hopup not working. The hopup-rubber may have flown off, quite typical.

 

BB not having any power is due to pistonhead not holding air. May have shredded, can happen.

 

Open the gun, its the only way to find out what really is broken.

[kojak]

My BB retention issue was "solved" by tightening the hop screw, with it all the way off there's nothing to hold a round in place.  When I first disassembled the gun I found a tiny rubber rod stuck in the piston cup that I assume was the stock hop nub.  

 

I could see how an AEG barrel/bucking could be fitted, but for my basic 1J build I decided to mod the stock parts.  All I did was clean it up and add a rigid curved rectangular shim between the screw and bucking for a noticeable improvement in consistency.  The next stage would be a simple "flat" hop (enlarged window, inner bump removal) with a more complex shim; probably a rigid layer with a malleable one underneath.  

[kojak]

This is what the back of the real wood version's mechbox looks like:  

 

 

I chopped that off and drilled a new hole for the RS grip.  With a bolt that isn't too long, a nut can sit just under the rearmost screw that holds the box halves together, and the whole thing can be reassembled by loosely installing the new grip before closing the mechbox, then sliding the receiver on over the front.  

 

 

Pretty happy with how it turned out.  I'm still trying to decide on a forend--I like the MOE, but I think the front overhang might go beyond the short barrel.