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