One of the most common "starter" or "1st timer" guns is the single shot shotgun. The most common single shot shotgun is the Maruzen based M870. In this post I will show you how to take down the gun and I will also point out a few neat tech tips on them aswell.
---Things to know---
The Maruzen/G&P m870s internal main spring is very close to a APS2 style spring and if you want more power you can cut down a spring and replace it with the stock one
---Notes---
The pics for this review come from http://www.justpistols.co.uk (giving credit where credit is due)
---What you need---
Pliers
Punch set
screw driver
---Step 1---
Remove the screw on the back of the grip (if your shotgun is a full stock model there should be a longer screw behind the butt pad or at the bottom of the grip)
---Step 2---
Unscrew the magazine cap and set it aside
---Step 3---
After the magazine cap is off slide the barrel off by pulling it forward
---Step 4---
Remove the pin with a punch as shown and unscrew the 2 screws above the safety and set them aside
---Step 5---
After removing the pin and the screws the trigger guard will slide off by pulling it from the body
---Step 6---
Slide the body back (away from the pump and barrel) The fake bolt should slide out aswell
---Step 7---
Remove the metallic arm as shown, it should lift right up
---OPTIONAL STEP---
This is where the Fixed hop is located, for a quick mod you can tap it for a larger hole and insert a set screw and now you have an adjustable hop up.
---Step 8---
Remove the highlighted pin by using your punch and slide the barrel and hop up bucking out. (make sure not to force this out, you dont want a ripped bucking)
http://www.justpistols.co.uk/ca_11.jpg
---Step 9---
Unscrew the magazine tube and lay it aside (some clones dont have a threaded tube and they are just separated with out unscrewing.)
---Step 10---
Unscrew the highlighted screws and like a mechbox carefully separate the top from the bottom
---Step 11---
Remove the cocking arms from the assembly (some clones have to be "forced" and some offer small set screws you have to unscrew)
---Step 12---
Remove the cylinder and piston assembly from the gun by lifting up on it to access the spring and spring guide