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#1 popatachi

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Posted 05 November 2009 - 11:11 AM

Here's my RSCB'd BBB. I have done some previous modifications which will not be part of this write up. These include: a stronger replacement spring, reinforced catch, electrical tape and o-ring around the plunger head to help flare the plunger.

For this modification I wanted to try and reduce as much dead space as possible and still get an easy to load RSCB.

Materials:Big Bad Bow
1/2" PVC elbow
1/2" PVC Tee
1/2" PVC tube (6 3/4" for darts, 2" to nest barrel, 1" for connection)
CPVC tube (6" for barrel, 1/2" for connection)
CPVC end cap
PETG (for breech or another material)
PVC clip
Extria screws
Tools:Dremel
Zap-a-Gap
Plumber's Goop
Files
Electrical Tape
Step 1. Modify the front cap, ring, and elbow
Most modifications start with attaching a coupler to the front cap and nested CPVC into the barrel and filling the dead space with hot glue. I opted to try a different method of attaching the PVC elbow directly into the front cap. This will reduce the dead space and not require a lot of hot glue in the process.

To do this, you will need to cut off the exposed area of the front cap and widen the hole in the cap until the PVC elbow can slide through. Try to get a good fit and not widen the hole too much.

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The white ring that was part of the air restrictor was used to help support the PVC elbow. The hole had to be widened just a bit to be able to accept the elbow. Once the PVC elbow can go through the ring, glue the ring to the front cap. Be sure that the ridge is facing the front to the cap.
I used goop in the front of the ring and Zap-a-Gap at the back to make sure no air can get through.

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As for the PVC elbow, I had to file down the inner area to allow the elbow to reach a little further back into the cap.

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In the above photo, notice on the left side of the PCV wall with trimmed straight. I did this to both the elbow and the tee just so that it matches.

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Step 2. Modify the BBB Shell
There are two areas that need attention. The bottom of the barrel opening and the front handle.

I removed the bottom lip of the barrel opening to allow the PVC elbow to get even further down into the plunger tube so it can be as close to the plunger head as possible.

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The front handle was removed so that the PVC that will hold the darts can be added in this area. Sand the area flat. The front handle will not be used and can be discarded or saved for future modifications. Optionally, you can move the location to the RSCB barrel to above the blaster if you want to keep the bottom for an integration.

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Step 3. Create the RSCB
To remove more dead space, take the PVC elbow and cut half of the tube that will connect to the PVC tee and do the same to the middle tube on the PVC tee. Make sure to get these as straight as possible.

Take your 1" connection PVC tube and dry fit these pieces together. When you are satisfied with the fit, use goop or Zap-a-Gap to secure the assembly.

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You have different options for your barrel, but I opted to use a 7" length of CPVC nested in a 2" length of PVC. The important part of the barrel is to cone out the end that will be put into the PVC tee. I used a dremel to cone out the CPVC enough to allow a dart to fit in about 1/4". Once you have your barrel, dry fit this into the PVC tee.

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Now take the 7" length of PVC and attach that to the other end of the PVC tee. Take the CPVC end cap and cut it in half. You may need to dremel out the inside if there is a ridge at the back. Take the CPVC connection and glue it into the end cap. Attach this cap to the PVC dart barrel. It should have the same diameter as the PVC.

I opted to create a breech so that I wouldn't have to pull the barrel off to reload. Cut a 3" hole into the tube, nest PETG with electrical tape wrapped around the ends and glue on a tab.

In order to quickly see if there's a dart in the barrel, drill two holes through the PVC tee and cover these with plastic and secure with glue.

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Take your RSCB and dry fit this into the BBB shell.

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Step 4. Glue
You don't need to glue the barrel and/or the dart holder if you want to be able to remove either of these pieces.

Now take the assembly and glue the elbow to the white ring in the BBB's front cap.


Step 5. Seal it up
I added electrical tape between the front cap and plunger to keep air from escaping. I also added some glue between the elbow and front cap at the opening for a little more stability.

Attach the PVC at the end of the dart barrel to stabilize the PVC. I also used some scrap plastic from a VHS box to help secure the front of the shell as well.

Step 6. All Done!
At this point the mod is complete.

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I was going to add a front grip with a 2" PVC but the connection point with the shell didn't have enough room for screws. So I'm looking into some rubber door stoppers to add to the sides of the shell to be able to grip the blaster as I'm priming it. In the meantime, you can hold the back of the front blaster to prime.

Ranges:
With a shorter barrel (6") and better plunger seal (flared out the plunger head) I am averaging 75ft with single BB stefans.

Edited by popatachi, 15 April 2010 - 08:00 AM.

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#2 Fredo

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Posted 05 November 2009 - 11:26 AM

Very nice. Finally a new guy that has some good mods. I guess it my time to start pulling my weight around here.
I always heard that RSCB's were horrible on BBB's. It just doesnt have enough air volume to overcome all the deadspace of the RSCB. Im guessing you would call it safe to say it hits sixties? Very nice breech by-the-way. Looking forward to see more work from you in the future.

Edited by Fredo, 05 November 2009 - 11:27 AM.

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22:24 Mr_BadWrench wait, you have a name that makes it possible for talio to seduce a woman?

22:25 Mr_BadWrench whats your name? john holmes?

#3 k9turrent

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Posted 05 November 2009 - 11:47 AM

Good job you copied my mod from about a year ago, but put it on a BBB

http://nerfhaven.com...showtopic=14991
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QUOTE View Post

That's about it. And thanks Angela who helped me with these pictures.. It looks huge in her hands.


HOLY CRAP!

FU ALL

#4 popatachi

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Posted 05 November 2009 - 11:53 AM

@Fredo: I've been around for a bit, but haven't had anything useful to contribute until now. As long as the BBB as a better spring and plunger seal, it should work well. 60's is probably about right.

@k9turrent: I totally did! I used a combination of yours and Mr. BadWrench's write ups on RSCBs to help me work through this thing. Thanks!
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#5 Zorns Lemma

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Posted 05 November 2009 - 12:23 PM

Smart move on the viewing slots, but they do make clear plastic PVC tube and fittings, if you'll be doing similar projects in the future.

I've never been one to believe that a BBB has enough plunger volume for an RSCB, but this seems to work for you well enough.
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#6 berserker

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Posted 05 November 2009 - 12:38 PM

I've also found, first-hand, the problems with RSCB'd BBBs, but I'll definitely try this mod out. ROF and plunger seal are the only reason my BBB sits unused. :[

And thanks again for the info popatchi, it'll definitely come in handy.

EDIT: I forgot to ask, do you have any problems aiming with a barrel that low? I assume it would be the same with the K9 special, but I've never had experience with it and was curious.

Edited by berserker, 05 November 2009 - 12:40 PM.

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#7 popatachi

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Posted 05 November 2009 - 01:07 PM

@Zorn's Lemma: I had seen the clear PVC and thought about it, but $6.00 for a single PVC tee just wasn't worth it, although it would definitely be sweet to have a clear RSCB. I use Ace Hardware's 1/2" FBR with a single BB that works well with this blaster setup. I haven't tried 3/0 weights yet, so I couldn't tell you if that would help or hurt. So far so good though.

@berserker: When I first tried this out, I kept tipping the blaster up to see the barrel, but I am getting use to the idea that I don't need to see the barrel to aim. As long as the RSCB is straight, it's just a slight adjustment when aiming.
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#8 Hi Yah

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Posted 05 November 2009 - 04:00 PM

Nice job. I personally think that bbb's work wonderfully with RSCB's.
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The yellow balls are also slightly smaller in diameter than the green ones.


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