My first mini: the Micro Raptor

Boom_erang · Posted: 05/11/2008 1:52 AM Post subject:

Thanks to all the great ideas I found around here on SF!

Presenting my first mini. The chamber is two Nalgene 1oz jars, glued back to back with LockTite plastic superglue (this stuff really works!) The forward jar is for storage, while the rear jar is the actual chamber. The barrel is a 12" piece of metal tubing with a 1/4" bore. At first I thought that it was steel because it definitely is not aluminum. But just tonight I tried sticking a magnet on it, and it does not appear to be ferrous material. Hmmm. Well, I found it lying around work so I'll ask around as to what it might be.

Ignition comes from a piezo element from a Scripto long-stemmed lighter, with solid wires soldered to the terminals and inserted directly into the chamber via small holes. I got the butane cartridge, tubing, and the brass tip (where the gas goes into the chamber) from same.

I used a 10CC syringe to figure out that this chamber needs about 1.5CC of butane for optimum combustion. I had calculated .9CC, but it did not turn out to be correct. Maybe my math is off... So my method for charging the chamber is to count about 2.5 seconds of butane from the cartridge. Fires every time and packs quite a punch! (video coming soon).

The ammo I made from brass rod and from aluminum stand-off posts. I used my drill press as a lathe of sorts to shape the rod into a bullet with a file. The aluminum bullet is faster because it's mostly hollow and thus about 1/2 the mass of the brass bullet.

As you can see from the damage pics, this thing will penetrate cardboard with these bullets.

The only problem is that often the cap will fuse to the jar and I have to work at it to get it off! So I added some oil and it helps. Any other ideas out there to prevent the polypropylene from fusing from the combustion heat?