After seeing this write up on a semi auto magstrike on NH:
http://nerfhaven.com/forums/index.php?showtopic=21373
I fell in love, however that love was not strong enough to shell out $40 for a shotblast.
Then came the megastrike that Lefty posted:
http://www.oznerf.com/t3658-megastrike-mega-missile-magstrike-reshell
I had a MM lying around and a Magstrike which I never use... so I guess there was no reason not to finally give this a shot!
What you need:
Megamissile tank
Magstrike
Check valve - I got mine from an aquarium store
Tubing to suit check valve - I am using 4mm aquarium tubing because that is also the size of the magstrike tubing
Barbed Connectors for your tubing - again, 4mm fits the standard magstrike tubes!
Alright, similarly to Lefty's arrangement - Cut down your megamissile pump tube and place a barbed connector inside it then block up the end with epoxy putty and seal with araldite
Next, the magstrikes built in air-fill button should be relocated to a position so that you can press it from outside the shell (the nerfhaven writeup placed it right above the trigger, however I chose the location shown due to personal preference)
Once you've decided where you want it, connect the button back to the bladder using your barbed connectors and tubing as shown:
Make any adjustments to your shell to allow the tubing to pass without getting squished and thus impede airflow!
Secure your air-fill button to the shell making sure it's positioned upright.
You can see that there's a green check valve connected right after the button - this is important to stop the air from being lost back through the button!
The check valve is connected to the barbed connector going into the Megamissile pump tube (as shown in the very first picture)
Connect whatever type of RSCB you want to the megamissile. I am using a weird arrangement of cut down PVC fitting + Conduit couplers.
This is because conduit couplers are smaller than the pvc couplers, allowing me to place the T-coupler lower in the shell (this allows me to better fit my RSCB setup inside the shell)
My RSCB clip with ball valve integrated into the shell so that I can open and close the valve from the exterior of the shell.
You will need to hack the shell a fair bit to get the ball valve to fit- otherwise you can simply use an endcap or something that sticks out beyond the shell, as seen in Lefty's pics!
Now connect the firing pin of the tank to the magstrike trigger - I drilled a hole into the trigger and tied a wire around the two parts to join them, make sure the wire is VERY taught or your trigger pull will not open the valve fully and lead to poor air output!
Finally you will have to cut a hole on the opposite shell to allow access to the air-fill button - the position of this hole depends on where you placed your button, so this is for you to figure out
I placed a black nub over the slim orange button to make the button push easier.
Screw that shell closed and you're done!
This is actually a fairly easy mod to do - it took me about 4hours of work to complete.
For those interested in seeing it in action simply check out the vid in the nerfhaven writeup... it's esentially the same.
The blaster performs very well - I haven't had a chance to range test it. I will try to make a video when I figure out how to work youtube... :S
One of my initial concerns was that the size of the tank might not suit the bladder pressure well, but it definitely performs above expectations- rough estimate it's just a little under the 4b power level.
I would also imagine that this could be done with an UMB tank since it's reportedly similar in size to the megamissile.
Hope you liked this write-up, feel free to ask any questions!