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Marrakai

“Quod erat demonstrandum”??? Well, I will let others be the judge of that!

However, since you have injected a mathematical theme into the debate; let’s do some maths. Let’s go back to no less an authority than John Taylor and his K - O values to put some perspective on things, viz;

STANDARD .577x 3” LOAD(750 gr @ 2050 fps),K-O= 126.7

STANDARD .577x23/4" LOAD(650 gr @ 1950 fps), K-O = 104.5

“MARRAKAI LOAD”(650 gr @ 1650fps), K-O = 88.4

I think the figures speak for themselves!

You will note that I have refrained from any mention of Kinetic Energy. Any system that places a 460 Weatherby Magnum ahead of a 600 Nitro as a gauge of stopping power has got to be flawed in my book. For a theoretical analysis of the validity of Taylors KO values, you could refer to T.R. Fowler’s Appendix in Elmer Keith’s book “Safari”. But, please, take his word for it; I really don’t care to be embroiled in debate on this score.

If it works for you, fine, but my suggestion is that if you can find a way of building a .577 Nitro that gets closer to duplicating the ballistics of the original 3” round, you would have a much more versatile outfit.

How you get there is another matter!

Since you seem to want to take issue on most of my points, I take it that your silence on the matter of larger capacity cases facilitating lower chamber pressures, is tacit agreement, so there is no point dwelling on that concept.

On any analysis, all things being equal, the standing breech on a 10 bore action has got to allow for thicker chamber wall thicknesses than a 12 bore. I eagerly await your metrological comparisons of the Zabala and Empire actions….

It would be dangerous in the extreme though to translate this into assumptions about relative action strength, since it is far too complex an analysis to undertake by the layman. Perhaps some Mechanical Engineering PhD student could find it suitable topic to write a thesis on?

I wouldn’t get carried away about the role of the underbolting in containing the forces of recoil. I changed my mind about underbolts when I saw an old hammergun once that has somehow “lost” it’s underbolt – the owner had been shooting is with a wire hoop that slid up over action and barrels! Happily shot the gun for years!

Somewhere, I seem to recall experiments done along the same lines where the gun was kept closed with gaffer tape, or some such. Can’t remember whether it was Gough Thomas or Burrard? Some day when I’ve got nothing better to do for a couple of weeks, I might try and dig it out. So, don’t ask me to come up with a published reference on that score!

Also interesting to note that, before Purdey came along with his underbolts, some guns were locked with effective top fasteners only. Westley Richards’ Model C bolting is one – I should have included that with the Rigby and Bissel, as one of the few systems that that actually worked!

On the pressure issue vis-a-vis jacketed and cast lead pills; perhaps you misconstrued my point?

Proof House pressure tests are a measure of CHAMBER pressure, not BARREL pressure. This is an important distinction, and it relates to the pressures that the barrels are subjected to further down towards the muzzle, and the concept that lead’s ductility leads to relatively higher pressures in that region.

Perhaps I was a little too cavalier in my original observation. Obviously, there are many factors at play; powder burning rate, lead/core hardness, jacket thickness/type, bore size, lubrication, etc.,etc. Anyway, this issue is quite peripheral. The point is, I believe that it is possible get lower barrel pressures with jacketed projectiles; whether you take that on board is entirely your prerogative………

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