Originally Posted by
LouisianaMan
I need to catch up on lots of things, including the .455 thread and the June 2018 Minutes of Her Majesty's S.A.A. (Revolver, Service, Webley .455-inch) Terminal Ballistic Science, Testing & Experimentation Board.
Pending fuller review, let me ask this: did you verify whether the conoidal-pyramidal-cylindrical &c. (I'm getting in the spirit here!) bullet shape tumbles in water jugs? I scanned your results with those nifty flat-nosed bullets and see that they did NOT tumble. My own shooting in various calibers .32, .38, .44 also has consistently resulted in flat-nosed bullets penetrating straight, nose-first. Round-nosed heavy bullets at low velocity were the ones quite likely to tumble, with .38 caliber efforts yielding most consistent tumbling with 200g LRNs at sub-600 fps MV. The British military spec for the .380-inch Mark 1/1Z 200g LRN was 590 fps, which corresponds closely with what I was finding to be the "sweet spot" when shooting water jugs.
In shooting CIS Mk 2Z 178g FMJ ammo of modern manufacture, I was observing a strong tendency to tumble. My impression was that tighter bores such as Colt and Ruger generally developed higher velocity, more stability, and were less likely to tumble. I should've done more shooting with Enfields when I had the chance, but having the largest dimensions and looser military/wartime tolerances, I consider them the most likely to develop low velocities and tumble after penetration.
That's safe with lead bullets such as the 200g, but that combination of characteristics is what gave the guns and Mk 2 FMJ ammo such a disastrous reputation for bullet-in-bore incidents when shooting low-powered or degraded ammo built to loose wartime tolerances. "Tolerance stacking" is the engineering concept Outpost explained to me, and it makes perfect sense even to this History-German major...!
So, is the lead, bottle-nosed .38-200 Mk 1 bullet, and/or in its guise as the Mk 2Z 178g FMJ, the "poor man's hollowpoint"? The low-pressure, low-blast, low-recoil way to enhance terminal ballistic effects without violating the Hague Convention restrictions against expanding bullets? Did the transition to jacketed bullets make a good thing go wrong?
And did the .455 in its round-nosed forms perform the same way, and thus show the way for reduction to .38-200? Given the dimensions of the .455" and .380" bullets, how do their surface areas compare in cross-section? Assuming that maximum terminal ballistic effect is achieved when the bullet is vertical, how does the "stopping power" potential of the two cartridges compare?
Let's say, for example, that the cross-sectional surface area of the 262g .455 bullet is 1.00. Is the 200g .380 bullet, say, .890? Therefore the .38 might be calculated as having 89% of the permanent crush cavity (aka wounding potential, aka "stopping power") of the .455, assuming (1) equal depth of penetration, and (2) equal number of revolutions as each bullet tumbles through its target.
Conventional Internet wisdom scorns the British Army's c. 1930 conclusion that their new .380" 200g LRN bullet offered essentially the same "stopping power" as their .455" 262g LRN bullet. If Fackler is correct in asserting that permanent crush cavity is the only thing that truly matters as a handgun bullet wounding mechanism, might the Brits have been onto something after all?
Do any of our CB engineering types care to calculate the cross sectional surface areas of the two bullets in question?