A newer, simpler, and more adaptable homemade spring-powered Nerf rifle.
Main Project Aim: Reduced cost and reduced machining time.
Secondary Project Aim:
+ Reduced plunger stroke length
+ Increased and variable plunger tube volume
+ Fewer parts
+ No "face rape"
+ Made from less than one square foot of a single thickness of polycarbonate
+ Easier to disassemble
+ One or fewer internal cuts required for completion
+ Easily upgraded with an optional pump-action foregrip
+ Optional stock
+ Wider machining tolerances for most of the parts
Length: 36 inches (with 12-inch barrel attached)
Plunger volume: 14.5 cu in
Spring load maximum: 30lb
Optimal Barrel Length: 12 inches
Individual results will be dependent upon too many factors to list so take these only at face value.
+ A Scroll Saw or both a Band Saw and a Coping Saw
+ Drillpress or Power Drill
+ 1/2", 9/16", & 3/4" size flat-blade wood-boring drill bits (a.k.a. "spade bits") + Mitre Box & Mitre Saw or a power tool useful for cutting plastic rod or tube (such as a table saw, circular saw, or band saw)
+ #6-32 Tapping Bit
+ Pliers or Wrench
+ Small round file
+ Flat file
+ Bolt cutters (for cutting spring)
+ Hobby Knife (to clean the edges of the sheets once cut)
+ Inkjet printer
+ Packet of full-sheet label paper
+ Electrical tape
+ Face Shield or Safety glasses
+ Super Glue
Make the process easier
+ 1/2" OD or larger 90-degree Countersink bit + Table Saw
+ Band Saw
+ Scroll Saw
+ Sandpaper or Sanding Sponge
No other tools expressly needed. All tools listed are not easily substitutable. You can cut out the center of one part using a Scroll Saw or Coping Saw, and a Band Saw could be used to make the external cuts more quickly.
All items available through McMaster-Carr
A full set of prices is included
Step 1: 1
Download the cuttings template sheets: 2-11.doc (236kb)
Print them on full sheet label paper. The included legend will tell you what size holes need to be drilled where. Most of which are labeled with the bit size or tapping requirements.
The template is laid out in the easiest way for quick machining, so simply use a pair of scissors to trim off the margins of the page. Adhere the labels to the plastic sheets, then cut the sheet into sections as shown to make the later drilling process easier.
Arrange the cutting templates on the thicknesses of polycarbonate sheet indicated on each template. It's quite easy to fit all of the needed parts onto each 12"x 12" sheet of polycarbonate.
Keep enough of a gap between the templates to allow the blade of the scrollsaw to cut inbetween the parts. Once you have them arranged, remove their backing paper and apply them to the protective film on the sheets.
Step 2: 2
Using a mitre saw with box, table saw, band saw, scroll saw or circular saw cut the 1-1/4 SCH40 PVC Coupler in half along the mold seam. Any nubs on the outside of the half you will be using will need to be filed or sanded down.
Step 3: 3
Add 2 or 3 wrap layers of Electrical Tape around the coupler half near the cut end until it wedges nicely into the end of the plunger tube.
Step 4: 4
Using a 7/64" bit in a drillpress or power drill, drill through the plunger tube and coupler half. Then tap the hole with a UNC #6-32 tapping bit and install a #6-32 3/8" length screw.
Step 5: 5
Repeat Step Four every 120 or 90 degrees. until the coupler half is secured with 3 or 4 screws.
Step 6: 6
Loosen all of the screws a little bit, then lightly use a rubber mallet or hammer to tap the bushing of your choice into the coupler half. Re-tighten the screws and it will completely lock the bushing in place.
Step 7: 7
Using a mitre saw with box, table saw, band saw, scroll saw or circular saw cut the plunger tube to a length of 8-1/2" inches.
Step 8: 8
Using bolt cutters, heavy gauge wire cutters, or whatever other tool you have available that can grind the steel down, cut the spring to a length of between 7-1/2 and 7-3/4 inches.
This length may need to be adjust later to ensure that the spring can be fully compressed while still allowing the plunger catch the lock in the catch.
Step 9: 9
Using a mitre saw with box, table saw, band saw, scroll saw or circular saw cut one 8-1/2" length section, two 7-1/2" length sections, two 5-1/2" length sections, and one 3-5/8" length section off of the 1/2" diameter plastic rod.
It's important to cut the ends of these as squarely as possible so that the finished blaster is assembled straightly. While some deviation in alignment is alotted for, crooked ends will make for a crooked blaster that may not work properly. SO TAKE YOUR TIME WHEN MAKING THESE.
NOTE: If you plan on having both a STOCK and a FOREGRIP installed on the blaster together you will need four 7-1/2" length sections rather than two.
Step 10: 10
Mark the center of both ends of all of the rods.
Using a 7/64" bit in a drillpress or power drill, drill to a depth of around 1/2 of an inch. Then tap the holes with a UNC #6-32 tapping bit.
Step 11: 11
Take the 3/4" length hex spacer, 5/8" OD spacer, and a #6-32 3/4" length screw and assemble them as shown.
Step 12: 12
Make sure the #6-32 3/4" length is holding the 5/8" OD spacer firmly centered on the 3/4" length hex spacer. Install the 3/4" length hex spacer into the chuck of a drillpress or power drill and run it at a constant speed.
If using a power drill, clamp a flat file into a vice.
Use the surface of the flat file to shave a roughly 45 degree bevel onto the outer edge of one side of the 5/8" OD spacer. Then round off the transition from the bevel to the side of the spacer.
When finished set this piece aside.
Step 13: 13
Using flat-blade wood-boring drill bits in a drillpress or power drill, drill out the large diameter holes to the marked sizes.
Make sure the do this while using a scrap of plywood as a backing to make the piece easier to clamp down, and in order to prevent the bit from hitting the table of the drillpress or the surface you are working on.
Using a 7/64" bit in a drillpress or power drill, drill all of the holes marked as "#6-32". Then repeat for the remaining hole sizes using the appropriate bits as indicated by the templates.
Step 15: 15
Using a scroll saw or coping saw make the internal cut in the CATCH piece that connects the 5/8" and 5/32" diameter holes.
Step 16: 16
1. Using a countersink bit or stone grinding bit in a drillpress or power drill bevel the marked edge of the 3/4" diameter hole in the CATCH piece.
Alternatively this can be achieved using a small round file.
2. Use an X-acto knife to round off the transition from the bevel to the inner diameter of the 3/4" hole to achieve the profile shown by the fine-point sharpie line in the photo.
Step 17: 17
Use a band saw or scroll saw to make all of the external cuts.
Use an X-acto knife to clean the burrs off of the cut edges of each piece.
Step 18: 18
Using a 7/64" bit in a drillpress or power drill, drill the four holes needed in both sides of the GRIP-SPACER piece using the lines on the template as guides for where to do so.
Then tap the holes with a UNC #6-32 tapping bit.
Step 19: 19
Use #6-32 3/8" length screws to assemble the GRIP HALVES using the GRIP-SPACER.
Use a belt sander, flat file, or sanding block to round off the edges of the grip as shown until it is comfortable to hold.
Step 20: 20
Use a 7/64" drill bit to align the two TRIGGER HALF pieces together and apply super glue inbetween them. Use spring clamps or a C-clamp to press the pieces together while the adhesive sets.
Set aside for however long the adhesive instructs is required for complete curing. Typically one hour will suffice
Step 21: 21
Attach together the FRAME1 and FRAME2 pieces using #6-32 3/8" length screws and the 3/4" length hex spacer. Insert and align into the partial GRIP assembly as shown, then using a fine-point sharpie to mark both side of the pieces as shown to indicate the alignment of the holes.
Step 22: 22
Using a 7/64" bit in a drillpress or power drill, drill the four holes needed in both sides of the FRAME1 and FRAME2 pieces.
Then tap the holes with a UNC #6-32 tapping bit.
Step 23: 23
Assemble the CATCH and SHOE pieces onto the FRAME1 piece using #6-32 3/4" length screws. The CATCH piece should be oriented so that the side with the bevel is facing the FRAME 1 piece.
The screws do not need to be fully tightened as the CATCH needs to be able to slide freely in place.
Install a #6-32 3/4" length screw in the FRAME2 side of the bottom tongue of the CATCH piece.
Step 24: 24
Continue constructing the rest of the assemblies as shown.
Step 25: 25
Loop a rubber band around the lower 7-1/2" rod then onto the screw on the tongue of the CATCH piece before attaching the two assemblies together with #6-32 3/8" length screws.
Also attach the STOCK piece to the opposite ends of the 7-1/2" rods with #6-32 3/8" length screws.
The GRIP/CATCH/STOCK sub assembly is now finished. The STOCK is optional and removable provided you replace the lower 7-1/2" rod with another means of retaining the rubber band to the GRIP-SPACER.
Step 26: 26
Use a belt sander, flat file, or sanding block to round off the forward edges of the PRIME piece.
Using a #6-32 1-1/4" length screw assemble the PRIME piece, 3/8" OD spacer, and 5/8" OD spacer onto one end of the 8-1/2" length rod as shown so that the side of the PRIME piece with the beveled edges is towards the 8-1/2" rod.
Step 27: 27
Tap the through hole in the TRIGGER with a UNC #6-32 tapping bit.
Use a belt sander, flat file, or sanding block to round off the forward edges.
Install the TRIGGER into the GRIP using a 1-1/4" length screw. The screw does not need to be fully tightened as the TRIGGER needs to be able to rotate freely in place.
Step 28: 28
1. Make an indexing mark on the FRAME0 piece and plunger tube using a fine-point sharpie. Make another mark on the plunger tube at the center-line of the edge of PCROSS1.
2. Using a 9/64" bit in a drillpress or power drill, drill the mark on the plunger tube.
3. Realign the indexing marks on the two pieces, then make a mark on the edge of PCROSS1 through the hole you just drilled.
4. Using a 7/64" bit in a drillpress or power drill, drill a 3/8" deep hole into the mark on the edge of PCROSS1.
5. Then tap the hole with a UNC #6-32 tapping bit.
6. Secure the plunger tube to PCROSS1 using a #6-32 3/8" length screw.
7. Repeat the above 1 through 5 steps on the opposite side of the plunger tube.
Set aside the plunger tube for later assembly.
Step 29: 29
1. Slide the partly assembled plunger rod onto the 5-1/2" length rods.
2. Slide the FRAME0 assembly onto the end of the plunger rod then secure it to the 5-1/2" length rods using #6-32 3/8" length screws.
3. Slide the plunger spring on to the plunger rod.
4. Center two rubber washers on the PH2 piece, then slide PH3 and PH2 on to the plunger rod.
5. Secure PH1 onto the end of the plunger using a #6-32 3/8" or 3/4" length screw.
6. Secure the plunger tube onto PCROSS1 after spraying the inside of it with silicone lubricant.
Step 30: 30
1. Secure the 3-5/8" length rod onto FRAME0.
2. Using a 7/64" bit in a drillpress or power drill, drill into both sides of the 3-5/8" length rod through the holes in the sides of the GRIP HALVES
3. Tap the holes with a UNC #6-32 tapping bit.
4. Install #6-32 3/8" length screws into the new threaded holes to secure the 3-5/8" length rod to the GRIP.
Step 31: Optional Foregrip
Remove the front half of the blaster by taking out the screws as shown.
See Image 2
1. Insert the FOREGRIP piece into the 3" PVC gravity feed coupler and use it as a template to mark where to cut out a section of the coupler.
2. Using a coping saw, hack saw, or band saw cut the coupler as shown.
3. Use a flat file or sanding block to round off and smooth out the edges of the coupler.
See Image 3
1. Remove the catch parts from the back end of the plunger rod.
2. Attach the 7-1/2" rods to FOREGRIP2, then slide FOREGRIP2 onto the plunger rod.
3. Reattach the catch parts to the back end of the plunger rod.
4. Loop a rubber band around FOREGRIP2, then use an S-hook to loop it onto the bushing at the front of the plunger tube.
Step 32: FINISHED
You are finished. Just add a barrel of your choice.