Okay, since people have shown some interest in my tiny barrel break, I am posting a writeup. There isn't a whole lot of literature on BB's, at least not stuff that's moderately feasible for most modders. So, here goes.
Things you'll need:
BarrelBreak
2 identical spare o-rings
3/4" PVC
CPVC
5/8" Spade bit
Drill
Glue of choice, I use some 2-Part epoxy goo
One really long and not too thick bolt, and a nut to acompany
Some wire, or other perfered dartstop method.
Saw
ETC.
The finished product, extremely holsterable.
Priming option #1
For this way, you will need some sturdy wire, a key ring, and two kinda weak extension springs, I used Mav slide return springs.
Priming option #2
For this way, you will need some 1/2" PVC, and some kind of priming handle.
This is the first half of the internal mods.
Take the two o-rings, and slide them on the male plunger tube, so that when it fires, they absorb some of the shock. You can pad it anyway you like, but this way is the quickest, most repairable, and probably cheapest.
Then take about 1/2" long ring of 3/4" PVC, and sand out the inside until it will fit over the female plunger tube. This will add some precompression to the spring, which will have it harder to re-assemble it, but it gets the spring much closer to max compression.
This is the second half of the internal mods. Cut off the barrels, but make sure that you leave the structures that allow the PT to be mounted in the shell. Then, clear out the AR junk, and then use the 5/8" spade bit and a drill to slowly bore out the entire male PT. Then, cut AT LEAST 3" of CPVC, put some kind of dartstop on the end, ame sure that the dart stop does not warp the PT, and then glue the barrel in. I think that the BB could handle more barrel length, and it might be wise to make a breach for this instead of vacuuming barrels, just to ensure that the darts get all the way into the back of the barrels.
I know that the bolt is not shown in the pump action version, but it is a good idea to place a bolt through the shell to keep it together better. Just drill two holes near the front of the shell, one on each half, and put the bolt through, which you can see here.
That is all of the internal mods. Now, just choose which way you want to prime the blaster. The shell cuts are exactly the same for both, at least on the front end of the shell. For the pullback version, you will need to cut a slit in the handle area to accomadate the wire.
For the pump version, just follow jerm's witeup, here, cuz' I'm lazy, and because his pics are clearer, and because I followed his writeup with a few alterations to make mine.
http://www.nerfrevolution.com/forums/viewtopic.php?f=8&t=1822For the pullback version, take the wire, thread it throught the holes in the black peice, pull it tight, engrave channels in the black peice for the wire to rest in without scraping the guide pieces, and place the trigger inbetween the two strnds of the wire, so that when the wire is pulled, it seperates around the trigger. Then, just tie the wire onto the keyring, and pull the two strands of the wire through the slit you made in the back of the shell. THEN, take the two extension springs, and attatch one end to the wire that is threaded through the holes in the black pusher peice, and bending the spring over the bolt, attach the springs to the screw that is near the front of the tac-rail. This is easier to do if you attach the springs to the screw first, then once the blaster is all screwed back together, then attach the springs to the wire. The springs should be malleable and resilient enought that you can bend then into place. I will try to get a picture of this frontal assembly up soon, hopefuuly within a week.
AND THAT IS ALL!
But, you could follow THIS:
http://www.nerfrevolution.com/forums/viewtopic.php?f=8&t=4341 with alterations for the BB, and then each PT would be individually primed, and you could bypass the black priming peice monkeyishness altogether, and minimize that part of the shell off, resulting in the SMALLEST POSSIBLE BARREL BREAK EVER! (Maniacal laughter).
I know for a fact that this thing will shoot at least 35" with 1" Domers, and that's all I use in terms of ammo. I say 35" because that's how long my hallway is, and it's still in flight when it hits the door at the end of the hallway. So, I'd estimate about 50", as a relative maximum for 3" barrels, stock springs, and the compression rings.