I think that this project was always meant to produce a functional Vasa cannon. I think the ones recovered with the wreck might also work if you wanted to fire them, but since they are originals they arent for obvious reasons.
It is an amazing project, and wish I could see part of it in person!
We will cast the bronze gun this Friday, at 10 AM, in Tierp (north of Stockholm). I was there yesterday helping with the final cleanup and preparation of the mould. There should be some press coverage, as well as a full account in Tom Ward's blog. The iron gun last week was a test of the mould and foundry logistics. The plan is for a full series of ballistic trials on an instrumented proving range to assess range, accuracy and effect. Some of the rounds will be fired at a replica section of the side of the ship, to evaluate both how effective the gun is and how Vasa might have stood up to cannon fire. Test firing is currently planned for next summer, but that may change depending on range schedules and funding (it will cost about 1 million kronor/150,000 USD to do the trials). There will be film taken, both conventional and high speed, as well sound, doppler radar, pressure monitoring. Think an order of magnitude above a Mythbusters project.
The gun was successfully cast this past Friday at Tierps Järnbruk. We started heating about 2.4 tons of bronze around 8 am and poured at about 11. No difficulties, and we expect to take it out of the mould late this week (it takes about a week to cool down). Pictures should be posted on Tom Ward's blog today or tomorrow (http://www.vasamuseet.se/creating-the-cannon). Fred
The gun was successfully removed from the mould yesterday, no voids or flaws, and the alloy matches the original very closely. We will spend a few days cutting off the gate and gunhead, cleaning up flash and mould dross, etc., then the gun will come to the museum next Wednesday for chasing and boring.
On Thursday last week, Oct 2, we successfully proofed the bronze 24-pounder copy, firing four rounds without incident. The largest charge, at 3.3 kg of powder, gave a breech pressure of 72 mPa (about 10400 psi) and a muzzle velocity of 399 m/sec (mach 1.17). The service charge we will use in the full trials starting next week will be 2.65 kg, which gives a muzzle velocity of 362 m/sec (mach 1.06). The proofing showed that at a low elevation of around 3 degrees, this is enough to throw a ball about 900 meters. It also showed that even if the ball leaves the gun at supersonic velocity, it quickly decays to high subsonic and then stays there, due to the exponential drag increase at transsonic velocities.