May 8, 1999
Well, folks. I did it. I went out and bought a new "barrel". The new barrel is comprised of a 4' length of heavy walled (0.25" wall thickness) seamless steel tubing. Back of the envelope calculations say it should be capable of withstanding roughly 7000 psi but I don't plan on pushing the gun past 2000 psi (at the *extreme*)....
Which brings up the question, "How do you know what your chamber pressure is?" Well, in the old gun, I didn't. I just made some guesses based on the muzzle velocity (roughly 300 psi, btw). The new gun, however, has a removable, replacable breach (still a muzzle loader though). This means that I'll be able to tinker with different ignition and instrumentation schemes without having to buy a whole new barrel because my breach has too many holes drilled in it (or whatever). With this in mind, I plan on putting in a pressure tap so that I will *KNOW* what the chamber pressure is.
October 10, 1999
After having spent (off and on) all summer developing the gun mount, recoil system, igition system, and instrumentation system, I finally got off ass and fired the gun this weekend at the urging of Bob Fortune.
I loaded up the gun with the normal load of 35 grams of fg BP and let her rip with an extra rocket that I'd made up last summer.... Unfortunately the new barrel has much tighter tolerances than the old (Actually, this is a good thing for the future, but didn't work out so well this weekend.). This resulted in much higher chamber pressures than in the old system. Exactly how high is unknown as I didn't hook up the instrumentation package as I wasn't planning on doing any "serious" testing yet. At any rate, the sabot and rocket were blown to holy hell and emerged from the barrel as confetti. The recoil was quite significant and a 3/4" bar of solid steel that is integral to the gunmount was bent and rendered unusable (no biggy, 'tis cheap and easy to replace). In short, the gun was a real crowd pleaser with one hell of a roar!
So what did I learn? That the new system is much more efficient than the old. This means that I'll be able to back off on the size of the BP charges used to achieve similar results. This is good both from safety and financial perspectives.
Below are a couple pics of me setting the gun up at the RRS/PRS MTA before firing [Thanks to Bob Fortune for the pics].
January 17, 2000
Having spent the last few months thinking about the failure of the recoil system, I've got a new system drawn up that I'm reasonably sure should kick booty. 'Tis based on the shocks of a 1980 Caddy (cheapest shocks I could buy at the parts store). It will require some machining that my wife should be able to do shortly.
As always, I'll keep you posted.