This is something I've been working on recently. At MLF, shields are a huge threat that can only be directly countered with grenades and rockets, however carrying an extra blaster purely for rocket duty is an absolute pain. I wanted something that I could attach to my blasters that would still provide decent grenade launching ability. I acquired this set of BBUMB internals, and with some spare parts, set to work.





















I used the same coupler as I have for my other blasters. That way I can use attachments that I've already made, and the rocket barrel I've constructed will work fine with my older blasters as well.





The pump is a pretty basic piece, just the stock pump sealed in with a dowel for a new handle. It's designed to attach to tactical rails, specifically Rapidstrike side rails. As such, while it also works with Rapidstrike top rails, it's not compatible with a lot of other tac rails.







The trigger is just a small orange beam that connects directly to the pin release of the tank. Because of the setup, it has to be pushed forward to fire, rather than being pulled back. This is a little awkward, but I'm getting used to it.







Both the BBUMB itself and the pump use Slydev parts that I had lying around. They're certainly not the most secure thing around, especially considering their age, but they work for now. I do intend to replace and supplement them with more, or something better, to improve stability.



A perfect example of the incompatability issue. Because the troughs in the Rayven's side tac rail are slightly further apart than a Rapidstrike's, the pump won't fit onto the rail. This is not a big issue as I rarely use anything besides my Bullpup, but rather is a flaw with the Slydev style of tac rail attachments.



Here's the underbarrel BBUMB set up on an Elite Rayven. This isn't a setup I would normally use, as I generally don't use long barrel attachments, or my Elite Rayven.It's more just what looked good and what I had on hand at the time.



Like with so many of my more recent mods, the underbarrel BBUMB was made specifically for my Bullpup RS. It attaches to my micro Retal barrel attachment and the pump fits nicely on one of the side rails. This picture really shows off how long the attachment is, something that is sadly mostly unavoidable. There are aspects in which I could have saved a bit of length, but nothing really significant. Regardless, though this setup looks rather clunky, I can hold, fire and pump it relatively comfortably.



Performance is good enough, it'll send a rocket past 8 metres with decent accuracy, which is enough for my purposes. The OPRV kicks in after only 3 pumps, which is much faster than a stock XBZ's ~12. With a 3 dart attachment, it can fire darts with quite a lot of power, yet for some reason when using a 6 or 7 dart attachment, struggles to fire all darts. Since I built it purely for rocket duty, this isn't a huge concern for me.

I'm reasonably happy with how it turned out, and I look forward to using it at the next MLF. I was going to use it at the most recent MLF, but in a moment of stupidity I broke off the coupler *at* the event before any games, so never actually got to use it.