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No videos for two weeks...I was starting to have withdrawal spasms. Nice shooter.
 

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No videos for two weeks?

I uploaded one on Friday and one on Sunday...
My stupid YouTube account was on the fritz. Just saw them after your post.
 

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The handle is an awesome addition. Are you allowed to attach a full size bayonet in Germany?
 

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I have a similar pistol crossbow. Very cool!
I have to use two hand and my knee to cock mine, so you pretty much demonstrated how damn strong you are. You did it with such ease!
 

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Sure, I can attach a bihander longsword if I wanted to. But no pocket light. Go figure.
Are police the only ones allowed to attach lights in this manner?
 

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Sure, I can attach a bihander longsword if I wanted to. But no pocket light. Go figure.
There are stupid laws that are made by politicians who are ignorant about real life. Out here in California you can not own anything labeled a club; war club, billy club etc., but you can buy all the baseball bats you want. Also blowguns are illegal here too. The only reason for these laws seams to because they could.
 

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That's just awesome. Exactly what it needed! lol

But it needs one more thing: exploding bolts. They make aluminum shaft bolts for these things that are the same size as the plastic ones. They are hollow, with a screw-in field tip. I tested this, and it works. Apologies ahead of time for mixing metric and English measures.

The materials:
- Aluminum pistol crossbow bolt(s)
- 35mm 6d finish (small head) nails
- 4mm common nails or steel rod
- Roll of caps (for children's toy cap gun)
- Masking tape
- Gunpowder and/or flash powder

Tools:
- Dremel with cutting wheel
- Electric drill
- .12" drill bit

The steps:

1. Remove the field tip and set it aside. You won't use it for this project.
2. Remove the plastic rear vane piece from the aluminum tube.
3. Cut 1/2" off the end of the vane that gets inserted into the tube.
4. Drill a tiny 5mm deep hole straight into in the flat spot you just cut.
5. Insert a 6d 35mm finish nail into the hole. If it is loose, drop in some glue.
6. Using a dab of glue, re-insert the vane into the aluminum tube.
7. When that dries, drill a tiny hole near the rear of the aluminum tube. The hole should be purpendicular to the plastic 'feathers'.
8. Using glue, insert wire (or a tiny nail) into that hole. Cut flush with the tube.

That all prepares the 'shell' of the exploding bolt.
Now we prepare the 'head':

9. Cut a 35mm section of the 4mm nail/rod. One end should be cut flat, the other may be cut as a pointed tip.
10. Cut a cap from the roll. Cut diagonally, to allow as much paper to accompany it as possible.
11. Using masking tape, tape the cap to the flat end of the arrow 'head' you have made. Tape around the perimeter of the head, keeping the cap exposed. Use enough tape to make the head fit sorta snugly into the tube, but not so snugly that it is difficult to push in with your fingers.
12. Fill the tube with gun/flash powder, up to the head of the nail inside.
13. Insert the flat 'cap' end of the arrow head into the tube. Push it slowly, all the way in. When it contacts the nail and stops, pull it out approximately two millimeters.

Your exploding bolt is now ready! The amount of powder in it is roughly equal to that found in a .380 ACP round. I tested this on heavy duty cardboard boxes. Be extremely careful, as on impact it propels the 'head' straight out into the target and creates flying aluminum and plastic shrapnel. Once the vane shot straight back at me (hence the subsequent care in ensuring it stays connected to the tube), so use eye protection. Be sure that no one is in the target line, or near the target when it hits.

It would be waaaay cool to see Jeorg rapid-fire seven of these. :). I've been using them with an NCstar self-cocking compound xbow with shoulder stock, but will definitely get an all-metal Cobra and add a magazine and foregrip to it.
 

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Discussion Starter #33
I made a tip for those bolts that are in fact pistons for percussion caps. You can turn those bolts into explosive ones simply by filling them with gun powder. But that would be very illegal here in Germany, so I can't go there.

My bolts can be seen at 1:36 in this video:

[ame]http://www.youtube.com/watch?v=kb4gBguXX6s[/ame]
 

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I made a tip for those bolts that are in fact pistons for percussion caps. You can turn those bolts into explosive ones simply by filling them with gun powder. But that would be very illegal here in Germany, so I can't go there.

My bolts can be seen at 1:36 in this video:

http://www.youtube.com/watch?v=kb4gBguXX6s
Thanks joerg, i will try to create one by myself with the Pdf
 

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Percussion caps are in short supply here in the USA right now. And on researching it I find that exploding arrows are a gray area here. You can legally buy arrow heads that contain actual bullets that fire on impact, which are functionally almost identical to what I have constructed, yet some states indeed have regs against ammo that explodes on impact.

Anyway, the roll caps are very cheap and do the job. And at 33 cents per bolt plus the cost of powder, it it price-competitive with .223 or 9mm or 7.62 - and for me, a lot more fun :)
 

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Here are the changes:



On the left is the bolt as purchased.
On the right you see the shortened vane, with the inserted nail and the 2 caps taped to the head of that nail. You also see the 1.75" length of the #8, 16d nail that is used in place of the original field point. The nail is wrapped with enough tape to keep it in place until impact, which shoves it backward and detonates the caps.

Even the detonation of just the caps, without adding any gunpowder, is enough to propel the nail out of the bolt when shot into heavy cardboard.
 

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My path toward optimizing the Cobra:



The materials were all obtained at my local home improvement superstore. A happy coincidence is that the flashlight is the same outside diameter as 3/4" PVC. So that clip on the bottom fits perfectly.

The handle is 1" Sched 40. Turns out that PVC can be very inconsistent, so to find a piece that coupled correctly using the riser extension required an additional minute.



The shoulder stock is 3/4" Sched 40. I might try again using 1/2", and drilling/cutting it such that the ball end of the cocking handle serves as a hinge for folding. But the reality is that the fixed stock only adds six inches, so we'll see.

I'll wait until it's warm out to spray paint those pieces. Next up is to figure out a removable magazine to feed multiple bolts.
 

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Didn't like the light at the bottom of the handle. That control button needs to be right at hand:







It's three bucks worth of PVC total, and easy to configure. A saw, a file, a drill....
 

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A better shoulder stock. 1/2" PVC (the first was 3/4"), smaller, easy to remove AND locks firmly into place



And a prod enhancement. Spring steel, wrapped in electrical tape. Also twisted the string to increase tension, and pushed the prod as far forward as possible. Ear estimate perhaps 15-20% speed increase:



But added speed is really not a major benefit. What is beneficial is added momentum. So I'm putting lengths of 16d nail into the hollow aluminum bolts to increase their weight. It goes an additional 1/4" into solid wood than before the enhancements.
 

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A velocity followup. My mods made a difference, but not quite as much as I imagined. Used an iPad audio app to measure time from launch to impact (17 feet). Had the ipad near the point of impact, and added 19 milliseconds to the duration of the audio track to compensate for the time the sound of launch took to reach the recorder.

With the standard plastic bolt, average velocity of 5 shots went from 169fps to 192. Aluminum bolts went from 164 to 183, and weight-enhanced aluminum bolts from 158 to 178. So the average velocity increase is around 13%. Not what I imagined, but still not bad. As cocking is not difficult at all in the current configuration, I will definitely add some more spring steel to boost it further. I wanna get the weight-enhanced aluminum bolts up near 200fps if possible.
 
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