Hit rate- cannons vs mg

[Pongo]

Originally posted by 63tb
If the 20mm was superior (especially the Hispano) to the .50, why didn't the British and Americans use them for bomber defense? I see that they might be tough for hand-held positions but they would work in a turret mount, right? Wouldn't  a 20mm be a better defensive weapon too?

63tb

You could more correctly say
"As the 20mm was so supperior it is not supprising that the British, Americans, Japanese and Germans worked very hard to implement 20 mm defensive turrents"

[Pongo]

Originally posted by SunTracker
But that brings me back to my original point.  A pilot firing cannons would not have the same amount of shells in the air, nor the dispersion if firing with 1 or 2 cannons.

So basically it all comes down to this.  At the average engagement distance, would it be easier to land 20-30 hits with 6 50 cals (the average U.S. Armament), or would it be easier to land 2-5 cannon hits with two cannons (the standard cannon armament)?

6X800rpm=4800rpm.  4800rpm/60=80 rounds per second.  It would take a 1/4th second burst to down an enemy aircraft.  Though indiviudal machine guns could be ramped up to 950 rounds per minute by armorers.

Hispano MkII= 600rpm.  600rpmx2=1200rpm/60=20 rounds per second.  Figuring 2 rounds to down an enemy aircraft, it would take 1/10th of a second.  Figuring 5 rounds, it would take 1/4th of a second.

The parity load out for 6 50 cals is 4 Hispanos.
The Spit, Pony, Hellcat, Corsair, etc etc etc.
could all carry 4 hispanos. So you see by your own numbers the Hispano is twice as good as the 50, because you had to cut the battery in half to show parity.

[63tb]

The rear turret of the Lancaster comes to mind. That turret was fitted with 4 x 303s. Seems like they could have stuffed two 20mm in the same space (maybe even one). When shooting back at night fighters, you would want any hit to do maximum damage since you may not get another shot. Was the issue ammo storage? I guess a belt of 20mm would take alot more space than a belt of 303.  Or was it that all Hispano production was allocated to fighters only?

63tb

[Tony Williams]

They could fit a pair of .50s  instead of four .303s (just about - the total gun weight was still greater) but not a pair of Hissos. The 20mm weighed 50 kg, the .303 around 10 kg. It also generated much heavier recoil, needed entirely different ammo feed arrangements and so on.

TW

[GRUNHERZ]

4 20mm hispanos is vastly more effective and versitale armament than 6 USA 50 cal - end of story...

[Flyboy]

Originally posted by HoHun

Here's a comparison of a selection of the above numbers to the energy of a single projectile (relative to the 12.7 mm Browning M2's API):

Gun Type                Dam in #  Energy
.303 Browning AC          0.296     0.20
.50 M2 AC                 1.17      1.00
12.7mm Breda - SAFAT      0.95      0.55
12.7mm Ho-103             0.998     0.55
12.7mm UBS                1.15      1.28
13mm MG 131               0.92      0.64

Note that the two columns are not directly comparable - increase the right hand column by 17% for that, using the 0.50" M2 as a calibration point.

Regards,

Henning (HoHun) [/B]

can someone explain me how come the M2 0.5cal round has such higher destructive power over all the other HMG?

i can understand in the 20mm theres a room for variety in the HE content. but in the 12.7mm? the M2 is allmost twice as powerfull

[Tony Williams]

It is almost twice as powerful in terms of muzzle energy as the Japanese, Italian and German 12.7mm and 13mm guns, because they fired much smaller and less powerful cartridges (although the Russian 12.7mm is slightly better than the M2).

However, it is not twice as destructive, as the damage score shows. That is because the other guns fire HE ammunition.

Tony Williams: Military gun and ammunition website and Discussion forum

[HoHun]

Hi Flyboy,

>can someone explain me how come the M2 0.5cal round has such higher destructive power over all the other HMG?

Wel, compare the following rounds:

Round       Type    Mass g  v0 m/s  Chem% KE kJ    ChemE kJ total E kJ
12,7x99     API     112     890     2     17,0     4,8      21,8
12,7x99     AP*     112     890     0     17,0     0,0      17,0
13x64B      AP       76     710     0      9,7     0,0       9,7
13x64B      HE       72     750     3,5    9,6     6,6      16,2

* Figures from API with 0 chemical energy for comparison purposes

The 12.7 mm M2 fires a 50% heavier shell at a 20% higher velocity, giving about 2 times the kinetic energy.

Another reason it looks good is that I have used mixed belting for some of the other guns, as for the Breda-Safat and the MG131, while only using the most powerful round for the 12.7 mm M2.

(Differently from what Tony assumed, I have figured in chemical energy in my statistics, and the damage numbers are actually derived from Aces High tests by someone else :-)

Use the most powerful round for the MG131 and the 12.7 mm M2 alike, and the firepower of the M2 is not ca. 200% of the MG131's (what you'd get looking at kinetic energy only), but rather 135% per round. Figure in the higher rate of fire of the MG131, the M2's firepower per barrel is just 117%.

(And figure in the weight of the weapon, and the M2 ends up at just 68% in the firepower comparison.)

For a heavy machine gun that's really powerful regardless of the perspective, we'd probably have to look at the Soviet UBS :-)

Regards,

Henning (HoHun)