[Rob Philips]

Thanks, gents. Lively topic. We agree that high muzzle velocity is good for the capability to score hits. We are unsure about a quantification of this statement. We agree that the Janecek effort regarding "hit probability" is remarkable, and very relevant, even if we cannot (yet?) agree with the presuppositions of that theory.

We do not agree that hitting bombers was easier with low Vo weapons. I believe that a lower Vo was the trade-off in the wish to bring a lot of explosives to the bomber target, as that required a large caliber, meaning a large projectile that could accomodate a lot of TNT, or whatever mixture of the contemporary explosive compounds. Larger calibers meant lower Vo's, or elso the design of weapons that would become prohibitively heavy for use in aircraft.

The earlier thread mentioned by Juha shows that the explosives used by the combattants of WW2 were rather similar. Detonation speeds from 7.000 to 8.750 m/s. Density differences of up to about 35%. Compounds that were either already available during WW1, or were variants of that, with no major developments to this day - if we limit this statement to explosives based on chemical compounds, the so-called conventional explosives. But all that is not relevant to hitting capability, or probability. It is highly relevant to the capability to do damage. But for that, a hit needs to be scored first.

I like to re-adress attention to what I'm after: an understanding of the probability to achieve hits. This is meant in a way that strictly belongs to weapon technology, not to weapon system technology. The latter would include aiming aids, and human factors such as pilot skills. I proposed to leave that out of the discussion, at least for now, so as not to complicate matters too much in round one.

In an effort to direct the thoughts, I would like to use the comparison with hunting ammo once more. If the target is stationary, and/or if it needs a lot of energy to bring it down, you choose ammo with a single high velocity projectile. If the target is a duck in flight, you choose ammo with submunitions, a 12 gauge cartridge loaded with a lot of size 5 to 7 pellets, that deliver a cloud of projectiles at a certain range. This cloud of pellets enables you to hit the duck, flying at about 70 km/h, at all. You would have virtually no chance to hit it with a single .22LR round, even if your marksman skills were exceptionally good. One .22LR round would definitely kill the duck, whilst one size 6 pellet would not. The .22LR round would probably fly through the duck's body, spending only a portion of its energy in that body, but that would be more than enough to bring down the duck. A size 6 pellet, at a shooting range of 40 meters, would penetrate only skin deep, not nearly enough to kill the duck. Three pellets however would bring down the duck, killing it instantly, as his nervous system cannot survive the sensory overload produced by their impact. Three pellets out of perhaps 150 fired with the shot, in a cloud of about 2 meters in diameter, a cloud with sufficient pellet density to score 3 hits at that max. range of 40 meters.

This max. range of 40 meters is the trade-off. The pellets have a very low weight; they go out at about 350 m/s, and they lose their speed very rapidly. If fired at a wooden door from a distance of one meter, the cloud of pellets is small and very dense, blowing a most impressive hole in that door. If fired at the same door from 50 meters, chances are that the pellets shall produce tiny dents in the woodwork, nothing more spectacular than that.

Surely a WW2 fighter aircraft is not comparable to a duck. But the analogy could be useful, to find out which aircraft armament can be considered as the more effective one for the envisaged job of bringing down adversaries, given the non-guided projectiles of that time, the gun sights that were marvels then, but very poor tools to those who are familiar with computers, and the likelyhood that most pilots were common people, meaning average marksmen.

The 12 gauge tool has a game hunting track record of centuries. Apparently it is most effective. It uses a very rudimentary sight only. It enables marksmen of average skills to score on a regular basis. Which WW2 fighter aircraft armament came nearest to a comparable achievement?

Regards,

Rob

P.s.:

1. This was written & send before I had a chance to read the preceding 3 posts. I used many more words to make the same point as Kurfürst did.

2. Harri demonstrates to be a close reader. Shall try to match that and state that we also agree that muzzle velocity is a factor when talking about aiming error. I'm not sure how important that factor is. That may change as we proceed.