Monday, April 7, 2014

Bullpup V2 Writeup

Before I start this writeup I need to ask you for some help. This is just the "test writeup" that I'm posting before it goes on NerfHaven. If you can think of a name that is not already used for a bullpup, that would be great. Also, let me know if there are any problems or if I go into too much detail or not enough. Thanks.

Here is the writeup for the bullpup. This blaster does take time to make, but if you have used a scroll saw and a dremel before, you will be fine. Since this blaster involves using those tools, it will be in the +bow category.

- The rainbow clan for inventing the rainbow catch
-  Ryan201821 for the Rainbowpump and the handle templates
- Makeitgo for making the Multiple <keeping my blog clean>
- Andtheherois for making the Oltiple Morgasm

- Screw Cutter/Mini Bolt Cutter
- Circle templates (little thin plastic thing with shapes to draw)
- A Dremel/Rotary Tool
    - Sanding Drum
    - Cutting disc
- A Scroll Saw
- A Drill
    - 7/64, 5/32, and 11/64 bits
    - A countersink bit
    - 1/2" spade bit
- Tapping wrench
    - 6-32 tapping bit
- A saw that can cut PVC
- Hobby Knife
- A ruler
- A yardstick/long architectural ruler
- Sand paper with sanding block
- Sanding Sponge
- Sharpie

Before I start the parts list, I highly recommend buying the 1" and 1.25" PVC from your local hardware store to cut down on shipping costs. However, you can find most of the parts you need at . I will include the part numbers so you can easily find everything. For screws and other hardware, I am overestimating the amounts so you have extras. In order to find the screws and hardware on McMaster, just type in the info for the screw into the search bar.

- 8538K18: 1/2" nylon rod
- 9637k26: K26 spring
- 4880k44: 1.25” PVC tee
- 4880K21: 1/2" PVC 90ยบ elbow (2x)
- 48925K91: 1/2" PVC Pipe
- 48925K93: 1" PVC Pipe
- 48925K94: 1.25" PVC Pipe
- 4880k314: 1” to ½” PVC reducing bushing
- 9245k51: PETG tube 2” OD 1.75” ID buy 1'.
- 2044T43: 1/2" ID PETG tube. This is the kind used for barrels.
- 8574k281: ¼” polycarbonate sheet 6”x6”
- 9691K56: U-Cup seal 7/8" ID 1-3/8" OD
- 91735A146: 6-32 3/8" panhead machine screws--You need about 20 if you don't buy 50
- 91735A151: 6-32 3/4" panhead machine screws--You need about 8
- 90126A007: #6 Zinc-plated washers

You will also need to purchase from a hardware store:
(Buy more than two of each screw)
- 6-32 1 1/4” machine screw (3x)
- 6-32 3/4" flathead machine screw (2x) OR thin 3/4" wood screws
- 6-32 locknut (1X)
- Silicone/White Lithium Grease
- Plumber's Goop
- 3/4" thick wood. It doesn't matter what kind, but make sure it isn't too soft. Poplar is great for this.

Not from hardware store of McMaster:
- Maverick/Nitefinder catch spring or any catch spring with a diameter similar to those. You can probably fin a small spring similar to these in a hardware store though.

You're going to want to start off by cutting out a 24" length of 1.25" PVC. Use a hacksaw, dremel, or scroll saw to cut it nice and square.

Next, make a simple quartering jig. This one is the most simple one out there. Cut out a 2" by 2" cardboard square.


Try to place your PVC in the center and trace around it with your sharpie.

Line up the corners of the cardboard with the ruler and draw lines like this. Use the lines to make marks on your PVC.

Use your ruler to draw four straight lines starting from the marks on the PVC to the other end.

Now onto the bushing. You will notice that there is a part of the bushing that isn't the part that couples to the 1/2" PVC. Make a sharpie mark on this part of the bushing. Line up the bushing with the PVC like you are putting it in the pipe. Use the sharpie mark to make marks on each of the four lines of where you will be drilling the holes.

Wrap packing tape around the bushing until it fits snugly into the PVC. You want an air-tight seal, but you also want to make sure you can still fit the bushing in. Once you have used the desired amount of tape, cut of the excess. 
Put goop around the bushing like so and put it in the PVC.
Drill the holes where you made the marks and tap into the PVC with your 6-32 tapping bit. Use your countersinking bit on the holes and then screw the 6-32 3/8" panhead screws into the holes. If you did the tapping right, you shouldn't need to use more goop here.
Set the pipe with the bushing away to dry. Meanwhile, you will be making the handle. Print out the templates made by Ryan201821. These templates can be found on his Rainbowpump writeup here. There are, however, many modifications to be made to these templates. I just used a pencil to do this. 

First, extend the handle length by 2cm or 3/4" if you have a ruler without cm. Shorten the top of the handle by drawing a line 3/4" up from the small horizontal section. The picture explains it much better than I can. On the trigger guard (rectangle piece), draw a line to split it in half (2cm). On the trigger sideplates (big rectangle), draw a line 2cm in. 
Cut out the pieces and attach the handle and trigger guard to the 3/4" thick wood. Attach the handle sideplates to your polycarbonate. 
Cut out these pieces on your scroll saw. Once you are done, it should look like this:
Drill the holes using the key from the template (5/32 for the polycarbonate, 7/64 for the trigger guard). After that, take the paper off.
The final part of the templates is the trigger. I attached the trigger template to the polycarbonate and then modified it to look like this. You can make the trigger in any way you want except you have to have the 1.5cm rectangle part at the top. This can be seen in the picture and it is very important.
Next cut out the trigger. You can sand it down to make it more comfortable if you want.
Now you want to put the handle together. The first thing you want to do is to attach the trigger sideplates to the trigger guard with 3/8" 6-32 screws. You can also attach the trigger without the washers to help with alignment. To do this just use a 1 1/4" 6-32 screw and a 6-32 locknut. Line up the trigger sideplates on the handle like so and mark where the holes are with a pencil. Drill the holes on both sides with a 7/64" drill bit.
Screw on the handle with more 3/8" 6-32 screws and put five washers on each side of the trigger (if five washers is too tight, use fewer). Your handle assembly is now finished.
Next is the plunger head and plunger rod. To make the plunger head, you will need polycarbonate and the u-cup. First put the u-cup under the circle template and find a circle that is a little bit bigger than the u-cup. 
Trace two of these circles onto the polycarbonate. You will also want to trace the inside of the u-cup onto the polycarbonate. Do your best to draw a dot in the center of all three circles. A good way of doing this is by making two perpendicular lines through each circle and drawing the dot at the intersection.
Cut out the circles with the scroll saw and drill a 5/32" hole through each center dot. It can be hard to cut circles on a scroll saw, so what I recommend is to cut a crude circle-ish shape bigger than the needed circle and then sand it down with a dremel or even sandpaper until it resembles a circle.
For the plunger rod, you will want two 1 1/4" 6-32 machine screws and the nylon rod. Cut the nylon rod to 13". Now on the piece of nylon rod, measure 3 1/4" into it and make a cut using any kind of saw that you want.
Make dots in the center of the ends of both rods except for the long one. The long rod only needs one hole. Drill a 7/64" hole into the rod where you made the dots and make sure that the holes are about 3/4" deep. Tap the holes with your 6-32 tapping bit.
Secure the plunger head assembly on to the 3 1/4" piece of nylon rod with a 1 1/2" 6-32 screw. The small polycarb circle should be in the middle of the u-cup and the other two pieces should be on the top and bottom.
Now take another 1 1/2" 6-32 screw and cut the head off of it like the one in the picture below. This can be done with mini bolt cutters or some kind of cutting tool that looks like the one below. You can also cut the head off if you clamp down the screw and use a hacksaw. 
Thread the screw into both pieces of nylon rod. Screw it in evenly and make it so there is about a 1/2" gap between the rods. I recommend gripping the screw with pliers to help get it into the rod. To make sure the whole plunger rod assembly is straight, slide the piece of 1/2" PETG over it. If it isn't straight, make adjustments until it is. 
Now that the plunger assembly is finished it is time for the catch! This catch is a modified version of the rainbow catch that is scaled down to fit into 1" PVC. To start off you want to find a circle template that would almost fit in 1" PVC. It's ok if it is a little bit bigger but it can't be smaller. Draw three of these circles onto your polycarbonate, make a mark in the center, and drill a 5/32" hole in them.
Using the 1/2" spade bit, drill holes into the circles using the previously drilled holes as a guide. You are going to also want to cut catch piece like what is seen in the top circle. There are no specific measurements for this, but just try to replicate it the best you can.

Here are the pieces cut out. Make marks on the circular pieces of where you are going to drill the holes. To help with this, line up the middle (catch) piece with the hole in the circle piece and then make the marks on the outside of the catch piece. The marks should be around the area of where they are in the picture.

Drill those holes and tap them with the 6-32 tapping bit. There are four holes in the picture because I actually messed up the first time and made the holes too close together. Ignore the holes on the top and bottom of the pieces.

Screw together the catch using 3/4" 6-32 screws. It is good if the screws are hanging off the side a little bit. This picture shows the two circular catch plates and the actual catch piece fitting in between them. If your catch plate does not fit, sand down the edges until it does.

Once you make sure that the catch is put together properly (the catch piece can freely slide through the catch plates and the catch fits in 1" PVC), you can sand the overhanging screws down. Do this with your dremel's sanding bit or it will take forever. Now the catch should be able to fall all the way through 1"PVC. Cut the 1" PVC to 11.5"

 Line up the actual catch piece with the 1" PVC like this and draw lines on the outside of the catch piece.

To fasten the catch to the 1" PVC, you want to out the catch plates in the PVC so that the screws already in the catch are facing away. Make sure that the catch is flush with the end of the PVC and make 3 marks of where you are going to drill. You will be drilling into the front catch plate without the screw heads. Drill the three holes with a 7/64" bit and tap them with the 6-32 tap. Finally, fasten the catch with three 3/8" 6-32 screws. Everything is better explained in the picture.

Extend the lines you drew earlier to be the length of the catch.

Cut out these lines with a cutting disc on the dremel. The below picture will also help with figuring out how to fasten the catch.

Cut the heads off of the screws that you used to fasten the catch. Use the same tool that you used earlier to cut the long screw. Screw the catch back in. I could screw the screws in all the way without using any tools, but if you are having trouble grip the screws with some pliers and screw them in.

Time to use the PETG! Cut the PETG to 3.5".

Use your dremel sanding bit to widen the hole on the front catch plate until it snugly fits the PETG in it. Super glue the PETG in and you will be almost done with your catch.

This next part has an easy option and a hard option. The easy option will work, but the hard option is much more reliable.
Easy: Take your nitefinder/maverick catch spring, cut it to a length that looks like the length sticking out of the catch piece in the picture below, and hot glue or super glue the spring on.

Hard: You want to drill a hole in the top of the catch piece that will be able to fit the maverick/nitefinder catch spring in it. Don't drill the hole all the way through so that the spring will stay in place. I start with a small drill bit like 7/64" and work my way up to whatever size will fit the spring. If you don't have a lot of drill bits, just use a hobby knife to slowly carve away at the hole.

Now that the catch is done it is time to fasten the handle. To do this, measure 9.5" from the end with the bushing and make a mark.

Measure 2" from that mark and make another mark. Connect the marks with lines so it forms a rectangle with rounded edges.

Cut out the shape you just made using the cutting disc on your dremel. Use the sanding bit to sand the edges and make them round.

Now on the opposite side of the PVC from where you made the hole, measure 9.75" from the end with the bushing and make a mark. Draw two dots on your handle of where you are going to want to screw it in. Line up the back side of the handle with the mark and create two dots on the PVC that are lined up with the dots on the handle. Once you do that, drill holes into the PVC where you made the dots with a 7/64" bit and tap the holes with a 6-32 bit. 
Now tape the handle onto the PVC using duct tape. It helps if you take off the trigger. Try to line up the handle with the holes you just drilled and make sure that the handle is as straight as possible.
There is no picture for this step, but what you want to do is drill through the holes that you just made with a 7/64" bit from the top of the PVC (the big hole). You don't need to be able to drill all the way through, you just need to make marks on the handle.
With your 7/64" bit, make the holes in the handle deeper. 3/4" to 1" deep holes should probably suffice. Now line up your handle again and screw it in using the flathead 3/4" 6-32 screws.
Drill through the from wooden piece on the handle assembly with a 7/64" bit until you drill into the PVC. 
Now remove the handle. Tap the hole in the PVC that you just made in the previous step with a 6-32 bit. Countersink the holes you made to attach the handle with your countersink bit and countersink the front wooden piece on the handle assembly.
Line up the handle assembly with where you would attach it. Also line up the trigger where it would normally go on the handle and make a mark where the back bump part of the trigger touches the PVC. There aren't pictures for this step but you should be able to figure it out. Here's a picture of the trigger again so you can understand what the bump that I'm talking about is:
You have two options now. You can drill a hole big enough for the trigger to fit through at the mark or you can draw a rectangle around the mark and cut it out with your cutting disc. I opted for the second method, but either one will work.
Fasten the handle on again and this time use a 3/4" 6-32 screw to screw in the front wood piece from the bottom. You can also put the trigger on now.
Now onto the slots. To make the slots, measure 1/2" from the front of the handle assembly and make a dot on the line on the side of the PVC. Do this on the other side too. Now measure 7.5" from the dots and make another dot. Drill into these dots with a 11/64" drill bit.

Now it's time to connect the holes. First draw lines using a ruler from the top of one hole to the top of the other and the bottom to the bottom. 
This next step takes patience. You are going to want to cut across the lines that you just drew with your dremel's cutting disc. Don't cut too fast because you really want these lines to be straight. Remember to cut the slots on both sides.
Push the whole catch assembly into 1.25" body. Line it up so you can see the catch through the hole for the trigger.
Make a mark on the 1" PVC (catch assembly) where it is lining up with the front of the slot. Do this on both sides like always. Drill into these dots with a 7/64" bit and tap the holes with the 6-32 bit.
Take the 2" OD PETG and cut it to 5" long. Put it onto the blaster and line it up with the holes that you just drilled in the 1" PVC. You want to have about .5" of PETG behind the marks you made. Drill the marks with a 7/64" bit and tap it for 6-32. The picture should explain everything a little bit better.
Screw the the PETG onto the 1" PVC with 3/4" 6-32 screws.
Take your two 1/2" PVC elbows and put them together like in the picture. Use the 1/2" PVC to connect them. It really should be self explanatory. You can glue or screw the pipes together if you want to.
Take the 1.25" Tee and cut down the top a little bit until you can fit the elbows into it.
Slide the elbows into the tee with the PVC stub going through the side off the tee. Now put the tee onto the back of the blaster where the bushing is. Make sure the elbows get connected to the bushing.
You are now finished with your blaster! As you can see,  I chose to clean it up a bit. To do this, I rubbed rubbing alcohol on all of the PVC to get the sharpie off. I then took a sanding sponge to it and sanded down all of the words and barcodes on the pipe. This can take a little bit, but it makes the blaster look a lot better. If you are having problems with your barrel tilting down, find something that can be a spacer between the main body and the barrel and then glue it to the main body for the barrel to rest on. I have had no problems with my barrel.
This blaster has over 7" of draw and if you do it right, it should have an almost perfect seal. Use your preferred barrel assembly and materials and you will be wreckin' it on the field.
I really like this blaster design because it is very compact and it fires better than any of my other homemades including my rainbowpump.


  1. Wow that is beautiful! I'm going to have to make one of these. Well done, Drev--this blaster has everything that I'm looking for :)

    1. Thanks! It would be awesome if you made one.

  2. Everything is great, maybe add McMaster numbers for the NerfHaven version?

    1. I did add McMaster members for everything that isn't easily searchable on the website. Thanks.