About WW2 fighter aircraft firing power

[Harri Pihl]

IMHO the ability to hit the moving target is a key factor on firing power, therefore the aspects which affect the hitting probability have large influence on firing power. The best known example of this is the velocity of the projectiles; 50% increase in muzzle velocity increase hitting probability by five times according to some sources.

[Rob Philips]

Thanks, gentlemen. I excluded HE & I ammunitions from the discussion as it is very difficult to quantify their effects. It is clear that adding explosives to a round increases its effectiveness by a large margin. Have checked what Tony Williams has to say about this, on the site mentioned by Juha. Explosive power is mentioned, of course, but not quantified. Perhaps we can include into the equasion the kinetic energy of an exploding round. But first comes the ability to hit the target at all.

I introduced "sighting" of the guns, as expressed by Juha, as "pattern density" into the equasion. Harri hits the mark I'm trying to make, with "the ability to hit a moving target". Projectile velocity is less of a factor here than you might believe. Projectile velocities are about 800 to 900 meters per second at the muzzle, reducing to say 700 after 150 meters. 700 meters per second translates to 2.520 km/h, about four times faster than the top speeds of the aircraft involved. Max. muzzle velocity of conventional projectiles coming out of rifled barrels is limited; this cannot be increased easily. If a Vo could be raised to say 1.000 m/s, or 3.600 km/h, reducing to say 850 m/s after 150 meters, or 3.060 km/h, then that would be about 5 times faster than the fastest aircraft, lessening the projectile flight time to target by a factor 5/4 = 1,25 only. This would translate to a smaller leading angle in the deflection shooting required in aerial combat, but that would be all. I would be interested to hear how, as Harri said, some sources calculate an increase of hitting probability by a factor 5, if muzzle velocity is increased by 50% - if that would be possible. I would also be interested in a definition of "hitting probability", as that would indeed be the key notion in this matter.

Have once done experiments to determine the max Vo that can be obtained from a rifled barrel. Using custom made plastic projectiles, used for their light weight, with .223 cartridges fired from an AR 15 rifle, cartridges loaded to the brim to obtain max. propelling force, a max. Vo of about 1.500 m/s was achieved. This was found to be a limit, that could not be exceeded with these means. Vo's of WW2 aircraft machine guns are all below 900 m/s.

Regards,

Rob

[Stewart]

The reason that small increses in MV/BC are so much more effective is not because of the differances between target and projectile velocities as you surmise, but because you required less lead on a target apearantly moving accross the line of fire.

The USAF made many studdies and determined that the third power of the differance between any two MVs would show the differance in probability to hit. In WW-II the Germans determined that the square of the differances in MV was equal to the differance in hit probability. The Ruskis came to much the same conclusions, but then determined that weight of shell Vs the heavy American Bombers was more inportant as they were very easy to hit. later guns had much higher MV/BCs!