Sunday, September 11, 2011

Pedal Air Gun Ballistics

This is something I've been meaning to do for some time, but never got all the elements together for it.

The Pedal air gun has a good deal of power, and the thing to do is to fire it through a chroney at an appropriate backstop, weigh the projectiles, and publish the results. I had, after all been pushing this thing as a kids toy.

Most of the elements fell together this week. The scale, the Chroney, the weather, and an attempt at a backstop. Click the link and scroll down for a picture of the projectile, made from a 12 ga shotgun shell hull. For this experiment I fired 2 shots, one with a hull with the rear opening flared, and one with masking tape wrapped to make a close fit in the barrel.

Specs: Shell with flared end weighed 266 grains, and the one with the tape came in at 279 grains. A bit heavier than a .45 round.
Air gun pressure was 60 psi.
Measured velocities were 357 ft/sec for the flared projectile, and 366 for the one with the tape. This yields a power factor of 102, which coincidentally is the same as my CZ-82 9mm and right there with a .38spl service revolver.

The backstop is where things got problematical. Here's the setup:

Draped over a ladder were 2 pieces of carpet, with a woven hemp doormat about 3/4" thick in between. The thinking here was that the resiliency of the rig would absorb some of the energy. It probably did, but to be safe, I added a piece of 2 x 8 in behind. Shot #1 penetrated all 3 layers and bounced off the 2 x 8. The carpet hanging down the back would probably have stopped the projectile, but the 2x8 was good insurance. Shot #2 stuck in the 2 x 8. At this point, I quit.
Yes, through 3 layers of hanging carpet, and into the wood. The point on this is 1/4" dia and an inch long and the fuzz hanging out from under is the 3 layers of carpet.

So no more back porch ballistics. Any further tomfoolery will be done at the range.

1 comment:

Rivrdog said...

Don't take that to ANY range. You'll have a chance of either meeting a BATFE minion or having one of their snitches see it, then you go on their Destructive Devices watch-list.

Bad enough to blog about it.