Today I took what is likely the most impressive shot I have ever done, and the ammunition was nothing more sophisticated than an ancient hole punch wrapped in duct tape.
I've been trying to shoot through a piece of 1/4" steel plate for about 5 months now, ever since I upgraded the SCTBDC to high pressure bottled gas, and today I achieved that milestone of performance which very few spudguns will ever reach. The obvious solution came to me at work when I was looking on McMaster to see what kind of steel I should get for my APFSDS rounds. I saw "S7 tool steel", read the description, and realised that I already has some on hand, pre-sharpened. After a few scratch tests, I confirmed that it would likely be hard enough, and proceeded to convert it to a non-finned, non-discarding sabot type ammunition to save weight over the APFSDS format.
I loaded up the SCTBDC (which has a ridiculous number of different possible configurations now), using the 2" valve, 2" x 144" barrel, a 40 layer (~340 psi) disk, ~230 ci of chamber and the 150 gram hole punch, which weighed about 170 grams with the sabot and wadding (an old rag). The target was placed roughly 1" from the muzzle to prevent the unstable round tumbling, with 1.5" of wood and a bag of concrete behind it to avoid damage to my shed.
I then set up the camera to record the shot, and started turning up the nitrogen reg. At roughly 340 psi, the rupture diaphragm fulfilled its final purpose, and my 1/3 pound hole punch was propelled down the barrel at just over 700 feet per second, hitting the target 24 milliseconds later, and doing this:
After cleanly penetrating the plate and leaving a hole that looks a lot like the hole from a .50 AP round, the hole punch continued on to split a 2x4 in half, fly through a bag of concrete, and punch through the front of my shed. Sideways. I found the punch lying on the floor, bent about 45 degrees off of straight, with a point just as sharp as it had before it was shot. The only thing I can't do is prove that this was actually done with the SCTBDC, and not a .50 rifle with a carbide tipped AP round. You can however, realize that no firearm ammunition capable of doing this is available in my entire country.
