This is an airsoft m203 launcher for Moscart Grenades.....with rail attachment....designed for an M4, but will fit most standard rails.

It's shorter...as my barrel is short...(it's a genetic thing).

KNOWN ISSUES:

ISSUE #1:
The Spring-Switch locking mechanism to allow access for loading Grenades is tiny.
It works fine without gloves, but in the field it is difficult to reload.
I'm working on a better switch system and will update the project soon.

ISSUE #2:
The rail attachment on mine has cracked when fixing to the rail and tightening a little too much. I printed with it laying flat on the bed.
Maybe try printing it standing up (using a raft or brim to secure it) and that might add more strength. I'll upload a thicker rail attachment at some point.

Assembly Instructions:

You will need:

3 x 5mm x 3mm Neodynium Magnets
1 x 18mm x 9.5mm(ish) Spring
1 x 18mm x 5.5mm Spring

3 x 25mm M3 Button Head Machine Screws/Bolts
1 x 18mm M3 Button Head Machine Screw/Bolt

1 x 20mm M4 CountSunk Machine Screw
1 x 20mm M3 CountSunk Machine Screw
1 x 17mm M3 CountSunk Machine Screw
1 x M4 Nut (maybe Nyloc)
9 x M3 Nuts

STEP ONE:
Glue LauncherBarrelEnd to LauncherTriggerWell.
Fit Two M3 nuts into the fittings in the arch at the top of the LauncherTriggerWell.

STEP TWO:
Slide LauncherTrigger through gap in LauncherTriggerWell
(It's a tight fit, but it should pass without snapping).

STEP THREE:
Slide 18mm x 9.5mm Spring onto LauncherPin

STEP FOUR:
Fit LauncherPin into LauncherTriggerWell through the hole into LauncherBarrelEnd

STEP FIVE:
Push-fit LauncherSafetyAxle into LauncherSafetyMech.
(I had to shave the axle slightly with a craft-knife so that it fit).

STEP SIX:
Press 5mm x 3mm Magnet into LauncherSafetyMech and install into LauncherTriggerWell with the axle sticking through the hole.

STEP SEVEN:
Press the other 2 x 5mm Magnets into LauncherSafetyCover and then glue the cover to LauncherTriggerLid.
IMPORTANT: Make sure the polarity of the magnets attracts the LauncherSafteyMech. You should end up with the magnets separated by the lid with the mechanism moved from one magnet to the other. This is the catch which holds the safety switch in place. Without the magnets the switch keeps moving around.

STEP EIGHT:
Fit LauncherSafetySwitch to the other end of LauncherSafetyAxle.
Fit LauncherSpringSwitch into LauncherSafetySurround infront of the 1 x 18mm x 5.5mm Spring.

STEP NINE:
Press (I used a Soldering Iron to melt in) the nuts into LauncherSafetySurround.
Use the 18mm Bolt through the trigger and the 25mm bolts through the other holes and secure into the nuts.

STEP TEN:
The LauncherBarrel is affixed to the rail mount using the M4 Machine Screw and a nut push fit inside the barrel.
The LauncherTrigger Mechanism is affixed to the rail mount using a 17mm M3 and 20mm M3 from trigger end to barrel end respectively.