This is the Booster, a double plunger pull-to-prime Nerf pistol with swappable barrels. It uses two Caliburn plunger tubes, and either two 6" or two 5.5" segments of K25. It has separate triggers for each plunger tube, and with the swappable barrels can be used for many different scenarios.

Included are options for single, triple, RSCB, triple duck's foot, single Mega, single Mega plus two darts, and demolisher rocket barrels. The barrel swap system is pictured- in the front end of the blaster, two stubs of 9/16" brass are glued in, which mate into the barrel mount. The barrel mount can have 17/32" brass stubs glued in for a perfect air seal between the blaster and barrel.

You will need two Caliburn plunger tubes, mainsprings (one 11" K25 can be cut to spring both sides), two small (5ishmm diameter) catch springs, six dash 123 O-rings (standard Caliburn/Talon Claw O-rings), two half inch segments of 9/16 brass and an assortment of #6 screws. Should be nine 6-32x3/8, eight 6-32x1, but I recommend getting a few more assorted sizes in case. Also superglue.

Assembly is straightforward: put plunger tubes into their slots on the catch housing as a guide, screw the chassis rails on through catch housing, put the two catches into the housing with springs, screw the rear cap on, slide plunger rods through the rear assembly, put mainsprings on, screw plunger heads on, remove plunger tubes for a second, add one O-ring for seal and one for padding on each head, lubricate, place plunger tubes back over heads, seating into rear assembly. Glue two 9/16 brass stubs into the front end, add two O-rings to the inside of the front end, seat front end onto plunger tubes and screw into chassis rails. Screw the grip top and bottom together, stack triggers and put into the grip, put a screw through to act as a hinge pin for the triggers. Screw the grip onto the bottom chassis rail and rear assembly. Then screw the top and bottom rails on, and you're done.

For optimum performance for the barrels, you want a stub of 17/32 brass glued into their mounts, but it's not required. The duck's foot option takes 3 segments of 17/32 brass glued in to make the barrels. The RSCB will need two 6-32x1 ½ screws, one M3x20 screw (yes, yes, I know, I'll fix it for 6-32 one of these days), two nerf toy screws, and 6" of 17/32 brass for the barrel and 6"/ of 9/16 brass for the magazine.

Everything but the plunger rods and heads can be printed at 20% 5 walls, heads and rods should be at 100%

Sounds more complicated than it is. Good luck. Also big thanks to Mighty Shrub for the RSCB cap, and Sillybutts for the Cynthia plunger head I modified for this!!

I do sell these built at https://www.etsy.com/listing/1507828107/flp-02-booster-nerf-blaster .

Changelog:

9/22/23- Added new extended right trigger file. Use this one- makes the pull way better. Also uploaded some experimental catches that should have less friction. Additionally, picatinny attachments for fidlock magnets. They'll hold large fidlock magnets, and if you put one on the top and one on the bottom, you can space them 95mm apart for holstering.

2/13/24- Added better half spring plunger heads and better plunger rods. Also MXL spigots.

2/26/24- Added .zip of metric Booster files. These should fit M4 screws, but have not yet been tested.

3/11/24- Added stock option. Requires 6 more 3/8" screws. If you want to get a cheek weld, use the longer butt option. The shorter butt looks nicer, but puts your face too close to the plunger rods. Works great if you don't plan on getting a cheek weld, though!

3/17/24- added metric RSCB stabilizer. Also added spring spacer- to lighten plunger and get the possibility of a bit more FPS, use the small plunger head and put the spring spacer at the rear of the spring.

3/22/24- added correct RSCBmain. An intrepid and long-suffering builder discovered I'd accidentally uploaded the prototype RSCB part, which does not work at all. If said builder is reading this- once again, I'm so sorry!