Richard,
At issue here is proof pressure versus service pressure. The loads you actually use (service pressure) should be well under the pressure used to proof the gun. Believe, subject to correction, that the consensus is that service pressure is 2/3 of proof pressure so your 5,000 psi loads would be about right.
Here's a quote from the London Proof House web site:
"Proof firing. Guns that pass examination are taken to an enclosed firing room, where they are secured in a holding device, which is aimed into a “snail” bullet catcher, a box containing a lubricated and hardened steel spiral that can safely dissipate the momentum of a bullet. The snails used at the London Proof House are safe for bullets upwards of .50 calibre. The gun is then loaded with a proof cartridge that, depending on the type of gun, will produce 25% to 50% more than the theoretical maximum service pressure. the firing chamber is closed, and the gun is fired remotely."
Regards, Tim
