This slingshot is heavily based on a slingshot outlined by Joerg Sprave in the video "How to make a power steel slingshot with common tools". I have, however, slightly modified his design to simplify construction and allow for a later upgrade to add a whisker biscuit, which will allow you to shoot arrows with this slingshot (given heavy enough bands - See Joerg's videos to see this type of thing in action).

DISCLAIMER: This slingshot can handle very powerful heavy bands, and therefore this can be a very dangerous slingshot. It can injure and probably kill. DO NOT point this thing at any people or pets. This goes double when the whisker biscuit attachment is added. I take no responsibility for what you do with this thing once you build it.

The above being said....I just might try it out shooting paintballs at some point in the near future...

Step 1: Step 1: Materials

Materials
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2 - Simpson Strong Tie T-Plates (With an extra hole drilled in the center)
1 - Hyper-Velocity Slingshot Band Replacement Kit (This was out of convenience...for more power use Theraband Gold or Black)
4 - 3/8" Hex Nuts
4 - 3/8" Flat Washers
1 - 5"? Carriage Bolt (Pick a bold that fits your hand nicely)
2 - 3/8 x 4" Eye Bolts (Sold with nut attached...so really you need 6 nuts total if these are not present)
1 Roll - Black Duck Tape
A few feet of light twine/string (optional)
Krazy Glue (optional)
20 Gauge Hardware Wire

Tools
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Most of my tools are in the city at my brother's place since I normally have no use for tools at my apartment. I keep a small amount around just in case, so for this project, I actually did not use all the appropriate tools. I will outline what I used and what should have been used.

9/16" Wrench (Should use 3/8")
Adjustable pliers (Ideally use another 3/8" wrench)
Wire cutters
Needlenose Pliers

Step 2: Step 2: Attach Handle

Screw a nut as far onto the carriage bold as you can, and then put a washer on the bolt.

Run the bolt through the center hole of the plate, as shown.

Place another washer and nut on the bolt, and tighten.

I later cut the excess threads off the top of the handle.

Step 3: Step 3: Add the Posts

Decide how high you want your posts to sit. Keep in mind the higher the posts, the more the strain on your wrist. If you do not plan on cutting off the bottoms of the eyebolts, then you do not need to worry too much about this right now, and you can experiment to find a height you like.

The key thing here is to have the first nuts on the eyebolts at the same height. Once this is done, put the eyebolts through the plate from the top, and place a washer and nut on the other end of the bolt. Make sure the open part of the "loop" is facing away from the direction you will be pulling. Tighten.

I then put some Krazy Glue in the threads to, hopefully, make them less likely to loosen up.

Step 4: Step 4: Add Your Band

Bend the end of the band around the eyebolt.

Stretch the end and band together, and twist the wire around the bands.

This is not an ideal way to do this, but I could not figure out how to do a proper constriction knot, and I didn't have any appropriate strong string to tie these bands properly. Hopefully the wire holds up well.

For the proper way, check out constriction knots on YouTube.

Step 5: Step 5: Grip

For the grip I wound some string around the carriage bolt for 2-3 layers and helped it stick with some Krazy Glue. I then put about 5 layers of Duck Tape on the grip, over the string. This thickened the grip a bit, and made it nicer to hold onto. In the future I may upgrade the grip using something like what Mr. Sprave showed in the video I linked at the beginning.