
I picked up this blaster from my local thrift shop ($0.99) and other than a broken missile rod/peg, it worked (no missiles included).

I figured I'd take it home and have some fun. Normally, I'd open it up right away but it uses these peculiar screws with star-shaped (hexalobular?) recesses - for which I don't own a screwdriver. So this write-up really just documents a simple "external" treatment. If can open it up in the future, I'll add some pics and possibly some internal (e.g. airseal) mods.
But modding the barrels is easy enough - first, I hacked off the rods down the nubs on the turret.

Then I cut some CPVC into four 3" sections. I use 2" darts for my CPVC barrels but ofcourse you can use whatever lengths you like. The extra clearance was to accommodate the turret nubs (about 3/4") over which the barrels fit. A small bit (~3") of e-tape around each nub and the CPVC barrels fit tightly. Add some hotglue to secure the connections. And voila:

the ranges are not spectacular (probably not more than 40') and very variable. Since this is a trigger-less blaster (you pull back the blue handle to rotate the turret and then push forward rapidly to fire), the range depends on how hard/fast you push. Truth be told, I don't get very good results with my CPVC/dart setup - if I get around to picking up more brass, I'm going to replace the barrels.
I also bought this with other plans in mind (e.g. integrating the turret and cocking mechanism with a powerful spring gun) - so this may well be a temporary solution.
Anyhoo - enjoy!