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Gunner_361st
02-07-2005, 12:34 PM
Below is an interesting quote from "Fire in the Sky; Air War in the South Pacific" By Eric M. Bergerud. Page 208-209.

"Because guns were the most important subsystem carried by any fighter and were very important on bombers, it is worthwhile to examine the subject. Ultimately, after all, a fighter plane was a flying gun platform. Regardless of performance, a plane without sound armament was of little value. The basic equation was complex, and no definitive answer arrived until the development of the incredibly destructive minigun rapid-fire cannons in the late 1950's (which continue in use on modern jet fighters). On the surface the tarde-off appears simply one of bullets in the air, which would support machine-gun armament, as opposed to destructive effect, which favored the cannon. In reality things were more complicated. Rifle-caliber machine guns (.303 caliber or 7.7mm depending upon the nation) had a very high rate of fire, approximately 1,200 rounds per minute per gun. The guns themselves weighed about twenty-five pounds, which enabled an aircraft to carry more light machine guns, more ammunition, or both. However, caliber (usually diameter, sometimes length) can be deceptive. A .303 round weighed approximately half an ounce. A heavy machine-gun round-say, .50 caliber (12.7mm)-weighed 1.7 ounces. Consequently a heavy machine gun roiund had greater than 3 times the mass of a light round and could fire at about 700 rounds per minute. A 20mm (.80-caliber) cannon round weighed about 4.5 ounces and carried a small explosive charge to boot. Consequently the mass of the round increased dramatically with the caliber of the gun. These calculations led major European air forces and the Japanese to mount a combination of machine guns and cannons on their fighters.

The basic thrust of this argument gained many adherents in both the USAAF and the USN. However, the Americans soon decided on a different path that matched the demands placed on their aircraft. The Americans experimented extensively (often at British urging) with cannons and a cannon-machine gun combination on all major U.S. fighters. With the notable exception of the P-38 Lightning, the Americans decided that heavy machine guns were superior for fighters. The major reason American engineers decided so was because they conceived of fighters as being designed to shoot down other fighters. Unlike Germany, the United States never had to worry about strongly armed and armored heavy bombers. And as we shall see, no Japanese aircraft could stand up to a solid hit from a heavy machine gun. So the standard armament on most U.S. fighters was six .50-caliber machine guns. In theory (as the British tirelessly pointed out) this layout meant less weight (I.E. in lead) in the air during a sustained burst and sacrificed the extra benefit of an exploding bullet. However-the Americans would counter- it did mean more bullets in the air than did mixed cannon-machine gun configuration. For the Americans, the crux of the matter was the destructive power of the .50-caliber round. Although a cannon round would do more damage, a heavy machine gun's armor-piercing bullet, at most angles, penetrated any pilot armor and bore a good hole in an engine block. And if it struck an enemy from any rear angle, it bore a hole through the aircraft or embedded into something very vital, such as the engine and cockpit. Therefore it did not make so much difference, if the target was a fighter, whether the round was 1.7 ounces or 4.5 ounces: Either would damage the enemy. If one accounts for the larger number of rounds - again, the Americans would argue - one stood a better chance of striking the enemy. It stood to reason that several bullets from a massed burst of six machine guns would be more effective than two cannons with a lesser rate of fire. In addition, because heavy machine-gun rounds were lighter than cannons rounds it was possible to carry far more of them, lessening the chance of running out of ammunition during a fight.

With the Zero, the Japanese again fell between two stools. It had two rifle-caliber machine guns and two 20mm cannons. Both had serious weaknesses. A rifle-caliber machine gun fired quickly, but the bullet's mass was inadequate to cause fatal damage to a heavily built U.S. fighter unless the Japanese pilot was an excellent shot or very lucky. Moreover, a rifle-caliber machine gun, unlike a .50 caliber machine gun, could not penetrate the pilot armor at most angles; it would rip much smaller holes in fuel tanks but not necessarily do fatal damage to an engine block. Furthermore the potential effective range of a light machine gun was about 600 yards, but in practice it proved hard to strike home unless closer. Cannons and heavy machine guns in theory offered better range, but considering the gunsights of the day most kills were made inside that range. Still, at most ranges cannons and heavy machine guns were more accurate. And so excellent marksmen, which Japan possessed initially, could overcome this problem by using the Zero's manueverability to gain a very close shot and shred an enemy with light machine guns using a large burst. If they could strike home with the cannons, all the better.

However, in both cases the ballistic qualities of light machine guns and Japanese cannons were poor. Despite theoretical range, it was very important to get as close as possible with light machine guns, especially given that during a rear attack the bullet lost impact as the target moved farther away. In theory cannons should have compensated for this problem, yet in practice the Japanese 20mm cannon was a poor weapon. It's rate of fire was low, and the initial muzzle velocity (the speed at which bullet leaves barrel) was poor. To make matters worse, on early Zero models the cannon barrels - again, to save drag - were made as short as possible, further weakening ballistic properties. In short it was hard to hit a target with a Japanese 20mm cannon. It was easier to strike with the light machine guns, bu they were not likely to gain a rapid kill. It did not help that early Zeros only carried sixty cannon rounds (for each gun). Famous ace Saburo Sakai commented after the war: "Our 20mm cannons were big, heavy, and slow firing. It was extremely hard to hit a moving target. Shooting down an enemy aircraft was like hitting a dragonfly with a rifle! It was never easy to score... our opponents were tough."

Hope you enjoyed the quote. 'An open mind for a different view, and nothing else matters.'

Gunner

Gunner_361st
02-07-2005, 12:34 PM
Below is an interesting quote from "Fire in the Sky; Air War in the South Pacific" By Eric M. Bergerud. Page 208-209.

"Because guns were the most important subsystem carried by any fighter and were very important on bombers, it is worthwhile to examine the subject. Ultimately, after all, a fighter plane was a flying gun platform. Regardless of performance, a plane without sound armament was of little value. The basic equation was complex, and no definitive answer arrived until the development of the incredibly destructive minigun rapid-fire cannons in the late 1950's (which continue in use on modern jet fighters). On the surface the tarde-off appears simply one of bullets in the air, which would support machine-gun armament, as opposed to destructive effect, which favored the cannon. In reality things were more complicated. Rifle-caliber machine guns (.303 caliber or 7.7mm depending upon the nation) had a very high rate of fire, approximately 1,200 rounds per minute per gun. The guns themselves weighed about twenty-five pounds, which enabled an aircraft to carry more light machine guns, more ammunition, or both. However, caliber (usually diameter, sometimes length) can be deceptive. A .303 round weighed approximately half an ounce. A heavy machine-gun round-say, .50 caliber (12.7mm)-weighed 1.7 ounces. Consequently a heavy machine gun roiund had greater than 3 times the mass of a light round and could fire at about 700 rounds per minute. A 20mm (.80-caliber) cannon round weighed about 4.5 ounces and carried a small explosive charge to boot. Consequently the mass of the round increased dramatically with the caliber of the gun. These calculations led major European air forces and the Japanese to mount a combination of machine guns and cannons on their fighters.

The basic thrust of this argument gained many adherents in both the USAAF and the USN. However, the Americans soon decided on a different path that matched the demands placed on their aircraft. The Americans experimented extensively (often at British urging) with cannons and a cannon-machine gun combination on all major U.S. fighters. With the notable exception of the P-38 Lightning, the Americans decided that heavy machine guns were superior for fighters. The major reason American engineers decided so was because they conceived of fighters as being designed to shoot down other fighters. Unlike Germany, the United States never had to worry about strongly armed and armored heavy bombers. And as we shall see, no Japanese aircraft could stand up to a solid hit from a heavy machine gun. So the standard armament on most U.S. fighters was six .50-caliber machine guns. In theory (as the British tirelessly pointed out) this layout meant less weight (I.E. in lead) in the air during a sustained burst and sacrificed the extra benefit of an exploding bullet. However-the Americans would counter- it did mean more bullets in the air than did mixed cannon-machine gun configuration. For the Americans, the crux of the matter was the destructive power of the .50-caliber round. Although a cannon round would do more damage, a heavy machine gun's armor-piercing bullet, at most angles, penetrated any pilot armor and bore a good hole in an engine block. And if it struck an enemy from any rear angle, it bore a hole through the aircraft or embedded into something very vital, such as the engine and cockpit. Therefore it did not make so much difference, if the target was a fighter, whether the round was 1.7 ounces or 4.5 ounces: Either would damage the enemy. If one accounts for the larger number of rounds - again, the Americans would argue - one stood a better chance of striking the enemy. It stood to reason that several bullets from a massed burst of six machine guns would be more effective than two cannons with a lesser rate of fire. In addition, because heavy machine-gun rounds were lighter than cannons rounds it was possible to carry far more of them, lessening the chance of running out of ammunition during a fight.

With the Zero, the Japanese again fell between two stools. It had two rifle-caliber machine guns and two 20mm cannons. Both had serious weaknesses. A rifle-caliber machine gun fired quickly, but the bullet's mass was inadequate to cause fatal damage to a heavily built U.S. fighter unless the Japanese pilot was an excellent shot or very lucky. Moreover, a rifle-caliber machine gun, unlike a .50 caliber machine gun, could not penetrate the pilot armor at most angles; it would rip much smaller holes in fuel tanks but not necessarily do fatal damage to an engine block. Furthermore the potential effective range of a light machine gun was about 600 yards, but in practice it proved hard to strike home unless closer. Cannons and heavy machine guns in theory offered better range, but considering the gunsights of the day most kills were made inside that range. Still, at most ranges cannons and heavy machine guns were more accurate. And so excellent marksmen, which Japan possessed initially, could overcome this problem by using the Zero's manueverability to gain a very close shot and shred an enemy with light machine guns using a large burst. If they could strike home with the cannons, all the better.

However, in both cases the ballistic qualities of light machine guns and Japanese cannons were poor. Despite theoretical range, it was very important to get as close as possible with light machine guns, especially given that during a rear attack the bullet lost impact as the target moved farther away. In theory cannons should have compensated for this problem, yet in practice the Japanese 20mm cannon was a poor weapon. It's rate of fire was low, and the initial muzzle velocity (the speed at which bullet leaves barrel) was poor. To make matters worse, on early Zero models the cannon barrels - again, to save drag - were made as short as possible, further weakening ballistic properties. In short it was hard to hit a target with a Japanese 20mm cannon. It was easier to strike with the light machine guns, bu they were not likely to gain a rapid kill. It did not help that early Zeros only carried sixty cannon rounds (for each gun). Famous ace Saburo Sakai commented after the war: "Our 20mm cannons were big, heavy, and slow firing. It was extremely hard to hit a moving target. Shooting down an enemy aircraft was like hitting a dragonfly with a rifle! It was never easy to score... our opponents were tough."

Hope you enjoyed the quote. 'An open mind for a different view, and nothing else matters.'

Gunner

Yimmy
02-07-2005, 01:16 PM
"it was very important to get as close as possible with light machine guns, especially given that during a rear attack the bullet lost impact as the target moved farther away"

That is true, however I think the author is missing the point of the aircraft shooting the MG also moving.
Say an aircraft shoots when it is going 300mph, this means the bullet gets an extra 300mph to its muzle velocity.
Given than a .30 cal round only goes 700-900m/s in the first place, an aircraft diving at speed onto a target can give its rounds a muzzle velocity of 1500m's or more in theory.

Due to the increase in velocity, the .30 cal round will deliver vastly more energy into a target when fierd from the fast moving aircraft, than when fierd from a standing position.

When two aircraft are going head to head, the intercept speed of the bullet fierd and the target aircraft must be immense - easily capable of defeating pilot armour.

initjust
02-07-2005, 02:00 PM
Yimmy,

Check your math.

Convert the "extra" 600m/s the diving ac in your post would add to the bullet's velocity to MPH.

I'm curious to know which WWII ac could attain/survive that kind of speed.

Indianer.
02-07-2005, 03:07 PM
All I know is when my 50's hit that 109 it looks nothing like it does on the TV http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Yimmy
02-07-2005, 03:19 PM
Plane in a long moderate dive down onto an enemy at say, 600km/h, for a boom and zoom attack.
That is 600,000m's an hour.
Which is 10,000m's a minute.
Being 166m/s.

What can I say, workings out in my head arn't what they used to be! http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif
So it would push a .30 cal round at 800m's a second to near 1000m's. Still a heavy increase in energy mind, but I don't know how long it would take for the extra muzzle velocity to drop off.

Obi_Kwiet
02-07-2005, 05:48 PM
Remember the speed that the enemy plane is traveling away from you, too. If you fire a bullet that goes 2000MPh, and you are going 200MPh, and the plane that gets hit is going 1500MPh, the effect will be that the bullet will hit him at 700MPh. How ever if it's head to head, then the bullet will hit him at 3700 MPH. If you're both going the same speed and you hit him from the rear, than it will be as if you fired it from the ground.

Gunner_361st
02-07-2005, 05:59 PM
The speed of the aircraft would effect the kinetic power of the bullets, sure, but not to the degree one would expect.

Example.

The muzzle velocity (speed at which bullet leaves barrel) of the Browning .50 M2HB is approximately 2,800 feet per second. Lets convert that to miles per hour, a common indicator in aircraft speed.

2800 x 60 (for FPM) x 60 (for FPH). The result is 10,080,000 feet per hour. Then, we divide it by the number of feet in a statuate mile, 5,280.

10,080,000 / 5280 = 1909.09 Miles Per Hour

Thats the speed at which the bullet leaves the barrel. Now, if the plane is flying along at 300 miles per hour and say, strafes a stationary vehicle on the ground, it adds 300 mph to that speed... Which is approximately a 16% boost in speed and thus kinetic power.

We could get into some very advanced ballistic properties here, but I'll just name a few examples. Remember, gravity starts pulling down on the bullet as soon as it leaves the barrel; this is why when shooting at long ranges, weapons are vertically elevated to compensate for gravity, meaning that with a very long range shot, your bullet's trajectory is really a lob. This principle applies to all firearms, from pistols and rifles to enourmous artillery pieces.

But anyway. Hope you all are enjoying the reading. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

eddiemac0
02-07-2005, 09:53 PM
At first, I loved birds with cannons because I couldn't kill anything with MGs. When I finally learned to stop shooting dead-6 and take some BnZ snapshots, I learned that the 4-8 .50s approach with its high volume of lead can be very appealing. Especially in new pilots, I would assume that cannons are conducive to turn fighting: not especially a good thing for late war Germans and Japanese...

Just an idea...

fordfan25
02-07-2005, 10:35 PM
well in this game i like the 4 20mm config on the hurrican and f4u-1c the best. how ever IRL id just as soon have the 6 or 8 50.s. im not going to get into a "is the .50s right in PF" debate. i will say though that IRL what ever a .50 round hits on a fighter or bomber its going to go right threw like a hot knife threw butter. with in combat range of course. heck iv seen a 270 rifle "no armor percing" shot completly threw a cast iron dodge 318 v8 . iv also my self shot threw one side of the same 318 with my 30-30 win. neather of those guns are any thing close to a 50 cal.

one of the things i think lead to the US useing almost eclusivly the 50bmg in its fighters and bombers other than resones stated in the firt posters right up was resuply and matanince. its alot easyer to send one type of ammo and replacement parts across two oceans and keep them instock on bases than 2 or 3 types. also i would think that a rifle round would be cheaper and faster to make than a cannon round with explosives. also training ground crews on mantanince for just one type of weapon would be easyer right?

i think the US made the smart move at that time by sticking with the 50.bmg now by the time fighters like the mig15 ect or if the J or Ger woulda had big heavy bombers like the b-17 or b-29s then i would think maby going with a 20 or 30mm might have been the way to go. there big and easy to hit and youd need to duck in and out with fast shots to avoid being hit by there turrents or escorts.

most of this is IMO

sighnd your lord and master
FORD