I do not quite understand why ShVAKs are so crappy in AH as compared to 6 50s and MG151s.
Even if to go only by muzzle velocity, rate of fire and projectile weight ShVAKs are better. In addition to that there were some types of amunition for soviet guns that made them more effective than competitors.
Here is the data:
(Type Muzzle Vel. ROF Proj.Weight)
ShVAK(20mm) 800m/s 800rpm 96 grams
MG151(20mm) 780m/s 700rpm 90 grams
Hispano(20mm)860m/s 800rpm 130 grams
US M3(12.7mm) 800m/s 750rpm 43 grams
UB-12.7mm 860m/s 1000rpm 48 grams
MG131(13mm) 700m/s 800rpm 36 grams
US M4(37mm) 700m/s 130rpm 650 grams
MK-103(30mm) 580m/s 200rpm 330 grams
MK-108(30mm) 500m/s 600rpm 330 grams
NS-37(37mm) 900m/s 250rpm 735 grams
So, Hispano does look better, but that's the only 20mm gun that is better than ShVAK if to compare only by these three parameters.
Some of the more complicated metrics that can be used are:
weight of a one-second burst;
"quality" of a gun = (m*(v^2)*n)/(2*g*60*M)
where, m - projectile weight (kg)
v - muzzle velocity (m/s)
n - rate of fire (per min)
g - gravity acceleration (9.8 m/s^2)
M - gun's weight (kg)
Also, I heard statements that even one 20mm and 2 12.7mm have more destructive power than 6 12.7mm (these statements were based on tests and pilots' experience).
Here's an excerpt from TsAGI study (chapter assessing lend-lease aircraft):
"Soviet and foreign fighters differed significantly in the positioning and power of their armament. Central positioning of armament, typical for Soviet fighters, allowed for better concentration of fire than wing positioning, typical for US and British aircraft. And this was so even though the rate of fire on Soviet aircraft was reduced due to the synchronization needed to fire through the proppeller area. So that to increase concentration and effectiveness of fire, the british and americans were forced to increase the number of guns, which resulted both in increase of the aircraft weight and the moment of inertia relative to the nose-tail axis. Because of this the responsiveness of the aircraft to the pilot's roll control inputs was worsened. It must be noted that even though the P-51B and D (that had only machine-guns) had higher weight of a burst, their effectiveness of fire was lower than that of the La-7, Yak-3, and "Spitfire" armed with cannon."
Here's what Oleg Maddox (Il-2 game creator, long-time aerospace industry engineer) had to say about some of the ammo used in USSR:
"Also 12,7 mm rounds for UB, BK and UBT had versions with contact explosure.
Such shells(rounds) used mostly on IL-2 rear gunner UBT as well as on most Russian bombers.
Less use of such shells on fighters was in the first period of the war, but from 1943 all planes were supplied with such power rounds.
So there was each third with traccer and others with explosure...
It was much more effective than say German 13 and 15 mm MG and of course more effective than US and UK MGs (There was total replacement of weapon on the lend-lease planes. Even on aircobra there is known such replacement of 12,7 mm US MG's, but not so many replacements than on Lend lease Hurricanes, P-40s and Spits)
Lend lease bombers also had replacement of weapon. Say such as A-20 even had Russian design turret as much more effective than original.
So, if someone think that one high speed 20 mm cannon and one 12,7 mm MG on Russian fighters was not enough, should read Hartmann's description with comparison - One gun is more effective then 6 MGs on US fighters. (And of course is big advantage when cannons are nose mounted).
The old time docs comparison with shot-weight per sec isn't so correct and can be used only as a basic comparison in additional to type and explosure effect of shells/rounds."
[This message has been edited by Wisk-=VF-101=- (edited 03-02-2001).]
