Sort of reiterating what somebody over on the Proof Loads post stated, my opinion is that if you have to ask the series of specific questions you are asking, you should not attempt to do this yourself.

Good heavens, friend, of course it might fail!

Make no doubt about it, I personally think the British proof system is, from a safety standpoint, a joke, though I readily admit that a defendant in a court of law might find it of some value, inasmuch as courts of law are something of a joke as well. So yes, it does serve a valuable purpose, though it does not declare a gun safe for every use it might be or should be expected to survive. I believe Bramble's description of the British proof system definitively "proofs" my point.

In fact, I believe the British system, while it might separate some wheat from chaff, is dangerous to rely on IF, IF the person shooting the gun somehow thinks that he doesn't have to inspect and maintain and knowledgeably feed his own hardware every time he heads to the range. DITTO ALL OTHER SYSTEMS.

They all serve a purpose in CYA for the gunmakers but "proving" a gun DOES NOT mean it is "SAFE". It only means that it fired a certain load on a certain day and it stayed together when it was fired and if done at the British proof house, the work was done by some guy who didn't have to get his cousin out of his sisters bed long enough to load the ammunition.

This gun thing is inherently unsafe. It is not golf. I enjoy it and so do many blokes who read these posts, but let us never forget that things that go boom nicely can go boom in a decidely unpleasant way. And never forget that the early-number 1903 Springfields that blinded some Doughboys were EVERY ONE PROVEN, and with known-pressure ammo to-boot. {BTW, I've never heard of a Lee Enfield letting go like them, but then they were proven in Merry Old.

} But don't forget also that it can happen even to Modern Man, as it did with the SAKO's that were recalled a few years back.

I have no doubt about my own ability to prove a gun as I and, I might add, every other handloader does it all the time, literally every time we work up a load. If you don't know what I mean by this, please see my first paragraph above.

Putting it another way, IMHO, every time you change a load and fire a round of ammunition the pressures of which are unknown to you {and they all are unless you own and use accurate pressure testing equipment}, you ignore and indeed nullify the value of your gun's original proof and you step out into the realm of proof-testing your own gun.

Now, Sir, do you need John Bull for that?