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400 NE

Thank you for that.

The calculation that I did was as an exemplar for the person making the enquiry.

I didn't mention CIP Ave Max pressures.

The data that I used was the average from the actual pressure data published by A square for the cartridge. The Avg. 16 bore data was taken fron Hodgdons loading data 2007. The reason I used A squares data was to have a PSI figure rather than a long ton breach thrust figure so that the enquirer could compare apples to apples.

The origional breach thrust figure for the 450 3 1/4 is 17 tons, for the 450#2 it is 13 tons a reduction of 23%. That is significant IMHO where an perspective action for conversion is considered.
I didnt think that there was any point in my reply in confusing the issue by getting into the conversions. I just wanted to keep the enquirer safe.

My figure of 52,500 for the proof pressure on my rifle was simply an extrapolation to one decimal point of 3500 bar into psi.

None of the above was designed to be definitive stress calculations for the proposed rifle. Simply to explain to the proposer that using the proof pressure of the 16 guage as a safe figure for a NE working load was not necessaraly a simple proposition.

As to the proving process for rifles, I too am left a little bemused. You are quite correct in what you say, in that neither I, you or the proof house actually know what pressure that rifle was subject to during proof. To say that I have no idea is perhaps missleading. I have a good idea what the minimum pressure generated by that firing was. If their experience is correct (and I must assume from their many years of knowledge it is) then the rifle was subjected to a strain at least 30% greater than that service load that I gave them. I can only presume that their experience has shown them that rifles barrels during prooving do not fail through radial pressure but through breach thrust. Thus their process is designed to put all the strain on the action face and jointing.
I would also like a formula for a proof load for this and many other cartridges. If you know where one can obtain that data then I would welcome it. I do not have the equipment to produce that data although it must exist somewhere. That would be a much more reliable way to proove rifles.

I truly expected the rifle to be attached to a strain guage during prooving. I have reported what happened as it happened, I am not advocating it! The process is a legal requirment for me not a matter of choice.

Regards