Fields of Fire

CapnMac - That may be the crux of the difference. Ranges of these weapons were alot shorter than the shipboard weapons. The .50cal was preferred by pilots as it was lighter, carried more ammo and therefore less of a drag on the aircraft. The US was the only air force that relied on machine guns rather than cannon as the primary armament of their aircraft at the end of WWII. The British at first used .303 cal. mg's (The Spitfire I and Hurricane I each had 8) which could saw off the wing of a bomber such as a He-111. This was fine at first, but with great fleets of bombers attacking, more bang for their buck was needed. The later series of all British aircraft had 20mm Hispano's added to their amament. The MG's being used more to target the cannon. Late in the war the Germans used their 30mm cannon (Me-262 had 4 mounted in its nose.).

Although the Russians had a good 37mm aerial cannon, the US weapon was not in the same category. When I mentioned that it was like lobbing a grapefruit, that was because of the distinct arc that it had. It was virtually impossible to hit with it. The P-39 series was the only production aircraft to use it as Bell Aircraft was a great proponent of the weapon using it on various designs from the pre-war period. 

Maximum range of aerial combat was usually limited to a maximum of 500 to 600 yards. 400 yards was the usual range for convergence of wing mounted weapons, although it is known that the better pilots like their convergence to be closer to 150 yards, but would attack even closer than that if they could. P-38 pilots liked the nose mounting of their armament which didn't need convergence with its concentrated firepower at all ranges.

Mike T.

telsono

Even if the 20mm shell (HE) is at the end of its range, its an explosive ordinance and relies on fragmentation to cause the greater amount of its damage. I still say that what you were talking about is the damage done by a .50 cal bullet (AP) which was the standard gun on us aircraft in WWII.

Well, we may be dealing with apples and artichokes, too.

Air-to-air 20mm weapons differed significantly from surface-to-air weapons.  I want to remember that the aircraft weapons are Hispano-Suiza, the shipboard weapons weapons used by the USN being nearly universally Orlikons. 

Further, we clearly are not taking about the same  engagement ranges.  Air-to-air; plane on plane, the guns were set to converge at useful distances for flying, 3-500 yards out.

When on a surface vessel, you want to engage aerial  targets as far away as possible.  With the Mk 2 and later 20mm weapons that is 3000-3300 yards out, ten times aircraft dogfighting ranges.

Inverse square rule applies when dealing with the energy available to detonate a fuse train in a projectile less than 1" in diameter.  Especially a 0.27# (4.3 oz) shell with a 0.024# (1/3 ounce) HE charge.

USN pulled the 0.50 cal AAA guns very quickly from shipboard use, along with the 1.1" guns.  The .50 cal and 37mm guns had excellent use in aircraft, just not much use from ships.

Working from memory (it being long time since Surface Warfare school) the 40mm Bofors had  a surface ceiling of 6000 yards, twice that of the 20mm.  But, had even a worse record for actually detonating on contact with kamikazes, unless the round struck something substantial (landing gear, engine, main spars, etc,)

The 20x105mm round remains an excellent air-to-air weapon even today. 

The 20x72 and 20x110 shipboard weapons, not so much.

Best place to engage an aircraft aiming for your ship is when the CAP intercepts them 40-50 miles out, and the CAP adds their 1-2000 yard range to that 80-100,000 yards.  Otherwise the bakers and yeomen are  just out there creating ballistic FOD to deal with.

ddp59

shell will hit point 1st not sideways as that will defeat the fuses.

It will only hit point first if it is in atmosphere allowing the aerodynamics to rule.  If it is in vacuum, aerodynamics will not come into play, thereby allowing gravity to pull the shell down to the surface with the point still pointed in the original direction it was fired.  If it was fired level with the ground the side of the shell would impact first.  If it was fired upwards, the back edge of the shell would impact first.  If there is even a little bit of air pressure present, then aerodynamics will take over and it will hit point first.

Capnmac I would still differ from your explanation. Even if the 20mm shell (HE) is at the end of its range, its an explosive ordinance and relies on fragmentation to cause the greater amount of its damage. I still say that what you were talking about is the damage done by a .50 cal bullet (AP) which was the standard gun on us aircraft in WWII. Few US aircraft had 20mm cannon, The P-38, a couple of the P-39's (P-400 for one), P-61 and the Corsair F4U-1C (only 200 produced) were the only US aircraft to use it. although it was commonly used by other nations Spitfire, Bf-109, FW-190). In aircraft that had both weapons the practice was to walk the machine gun on the target and then fire the 20mm when you were on target using the machine gun tracer rounds to mark the hits. Usually there were only 20 to 40 2omm rounds against the 100 to 200 mg rounds. There was a separate switch to arm the cannon. 

I didn't mention the 37mm of the P-39 because it was like lobbing a grapefruit, hard to hit with, but one shell hit could destroy an aircraft, again because of the explosive effect and fragmentation.

Mike T.

shell will hit point 1st not sideways as that will defeat the fuses.

Yes, I guess it's true that a pointed shell would fly point first due to aerodynamics.   Aerial bombs, of course, have fins, so they'll point downwards.   Same with mortar shells.

ddp59

don't forget gravity as it will still bring a shell down even in a vacuum.

That was my intent.  That is why it would impact with the side of the shell when it finally landed.  If there was no gravity, and in a vacuum (no air friction) it would continue in a perfectly straight line until it impacted something in front of it.  If nothing was in front of it then it would continue forever.

Ah, but that is also the difference in air-to-air use of 20mm shells and in surface to air use.

Air-to-air engagements were much closer together.  The shooting pilot had a much better control to "walk" the shells on to something that would detonate a 20mm shell (which is only 5/6" around, with a rather small charge). Also, air-to-air maneuvering resulted in "showing"  a large aiming area to the other pilot.  Kamikaze attack is a dot that gets a line through it eventually.

Surface-to-air engagement distances could be 3000yds with a maximum ceiling of 10,0000', or about 2 miles.  At those ranges, the rounds are mostly spent.

Then, remember, you are engaging a target in a power dive, it's coming at you at 300-something knots. That's 35,000 feet every minute, giving you about 20 seconds of engagement time.  Every second that a/c is getting 585' closer--you need to knock a wing off or engine/pilot kill.

That 20mm round, at the end of its energy could pass right through the thin-as-a-coke-can skin on an aircraft.  This would leave a hole not much bigger than the round.  Even if the hit has enough energy to detonate the 0.001# charge, it's as likely to happen after going through the entire wing.

CapnMac - I might want to differ with aircraft armament, smaller caliber ammo up to .50cal are solid rounds primarily with also tracer rounds. (the Italians did have a .50cal with an explosive warhead, but it wasn't too good a weapon.) Few are explosive. The damage you illustrate sounds more like a .50cal hit. 20mm guns used shells filled with explosives and caused alot more damage on striking an aircraft, more than the 1-2" damage. Against the Japanese, our aircraft increased the ratio of tracer rounds with our .30 and .50 cal machineguns as they had a greater tendency to initiate fires in these aircraft without self sealing gas tanks. During Korea, the .50cal MG was found not to be an effective as an air to air weapon and was phased out with the 20mm cannon and gatling guns with explosive shells taking over.

Mike T.

edit:

This article supplies some technical details. Note the worst 20mm shell has twice the destructiveness of a 12.7 mm (.50 cal) bullet.

http://www.quarry.nildram.co.uk/WW2guneffect.htm

Recall that shells have a ogive shape, this generates lift and airflow.

As the velocity decreases the nose points down.  This continues until the attitude gets to near vertical.

The same thing occurs with aerial bombs--they start off horizontal, then follow a ballistic curve into the near vertical.

This is true for a 5" round at 12 miles as it is for a 16" round at 40,000 yards.

Note, that for separately-loading ammunition, you often use the same barrel inclination, but not as many bags of powder.   This can keep the ballistic curve similar, just with a different scale factor (handy when using a mechanically-geared prediction computer to solve for fall of shot).

Part of the AAA equation is also in how the a/c are built.  On the thin-skinned Japanese a/c a 20mm hit might make only a 1-2" hole through the sheet metal.  Unless you hit a spar or the controls or the engine or cockpit, the shells do not do that much.  (Well, other than giving the crew--stewards, signalmen, carpenters, yeomen-- "something to do"; thus the flight deck galleries on USN WWII carriers.)  Go up to 40mm and, if the round exploded, it was a pretty reliable "kill."  But, you have to hit something on the a/c, engine, gun/mounts, landing gear to have it go off.  until about '46, the smallest round a proximity fuse could be fitted to was 3".

don't forget gravity as it will still bring a shell down even in a vacuum.

I think it has something to do with the dynamics of air friction, but the point of a spinning bullet will always lead the way.  Regardless of distance.  Now if you are using a barrel shape like a .38 Wadcutter, then the bullet can tumble in mid air, but if it has a point, it will hit point first.  It may be wobbly, but the point will hit first.  The fatter rear of the bullet or shell has more drag than the point so it is always lagging behind.  If you were firing in a vacuum, then your theory would probably be correct.  The shell would land on its side because there would be no air friction to affect it.

Slightly off topic, but I was recently reading a book on the U.S.S. Houston, and it mentioned that 8 in fire at maximum range plunged almost straight down on the target.   That got me to thinking; since the shells are stabilized by their spin, a shell coming straight down wouldn't hit point first, would it?  It would still be oriented in the same direction as it was when it left the tube.

Am I missing something?  Seems like a shell hitting sideways would be more likely to be a dud, and with poor penetration.

Of course, they wouldn't really be straight down, but any look at a ballistic table shows things falling pretty fast at max range.

Yes, they were manned. Look closely and you can see they have observation hatches. I recall a Mk.37 has  several inches of armor, like a turret without a gun. The director has telescopes for line of sight bearings, and was used as an observation point for fall of shot. Even in a radar equipped director, initial line of sight for targets above the horizon might be optical.

AAA controlled by a Mk. 51 is optical, but those things are pretty local to the guns and not so armored.

bondoman

... I'm sure. I don't know much about it, but I did learn that, while modeling CA 38, the communication trunk from the director to the fire control center was heavily armored.

So the fire directors were manned by operators? Didn't realize that! I always thought they were remotely controlled from below.

Rusty

Lebanon was a very "close quarters" fight for much of the early days. Lots of bottlenecks and choke points on those mountain roads where anti armor helicopters and teams could really wreak havoc. A shot at 100m is barely inside minimum range for the missile. IIRC it does not arm until it travels approx 65m. During my active duty time as a TOW gunner I got to fire three of those very expensive fireworks. It seemed like time stands still for the 17 seconds it takes from the time you press the launch button until the missile impacts a target at 3000+ meters downrange. And that is with no one shooting at you... the Dragon missile I always thought was a good way to get the gunner killed in combat. The Javelin and Hellfire are a vast improvement in survivability.

stikpusher

 

There's also a story from Falklands where a British helo, probably a Gazelle, fired a wired guided weapon  like a Milan at maximum range toward s the Argentine HQ in Port Stanley, but they got scared off and the wire got stuck over the top of a hill and the munition went out to the harbor and narrowly missed a ship.

I always thought wg weapons were weird. But of course now I get spam calls on my iPhone selling me golf clubs when I drive through Pebble Beach, so who can say?

Glue Mark

 

"CAN HE DO IT? HELL YE.......!!"

bondoman

OT a little, but I have heard of tanks firing their main guns at attack helicopters. Could be effective against a TOW platform.

Not very effective though. The TOW was designed to keep its launcher out of effective range from Soviet tnak guns. One of the reasons its range was extended from 3000m to 3750m. But if the launcher is inside max effective range the tank has the advantage due to faster flight of a tank round vs the missile...

bondoman

Well if I was that pilot, I'd get good and low down between the BB and a DD! Might sink two ships at once!

Whew! Bondoman, you had me worried there for a minuet. At first I thought you were going to talk about "frying chickens in the barnyard!" like ol' Buck Turgidson in Dr Strangelove.

"CAN HE DO IT? HELL YE.......!!"

Rusty 

Well if I was that pilot, I'd get good and low down between the BB and a DD! Might sink two ships at once!

IMO the only real use for BB's after, oh about 1905 was for shore bombardment. Which they are fearsome deadly at.

In fact, when the CA 38 got hammered so badly at Guadalcanal, she was torn up by 5" gun fire from a bunch of destroyers. An unexploded 14" fragmentation shell from Hiei was found in her.

bondoman

Source, please. I'd discount that. First of all those big rifles took time to lay and fire, plus they were set for a ballistic trajectory. Others would know, but I would guess the minimum range to drop a shell in the water would be at least a couple of miles away.Plus, that attack was a dive profile to hit the deck at a high angle.

Fire control is the answer, I'm sure. I don't know much about it, but I did learn that, while modeling CA 38, the communication trunk from the director to the fire control center was heavily armored.

I can't remember for sure, but I think it was a book about the Iowa Class BBs that I had borrowed from the local Public Library, which would have been back in the early 70s.  It seemed a little difficult to believe to me also considering the speed the planes traveled versus the speed the turrets could turn and train the guns to a specific spot, but they explained that the guns could depress something like 3 to 5 degrees which would give them an impact about a mile or so away.  Some of the kamakaze would come in at wavetop to hit like a torpedo, and these were the only ones these guns could be used on.  I would imagine they would have to be already trained to a specific distance and if a spotter saw a plane approaching that vector they would tell the gun captain when to fire so as to create the wall for the plane to hit.  So the opportunities would be very few.  I can only imagine what it would look like if a shell did happen to hit the plane directly.  A whole lotta energy released in a small location.  Even if the shell didn't explode, the sheer impact should disintegrate the plane.  A 3 ton plane at 300 knots versus a 1 ton shell at what, 2000 knots, in the opposite direction? 

I would think that if it actually happened there would be some kind of Action Report crediting a Main Battery crew with downing a plane.  Or a picture of a turret or barbette showing a downed plane instead of just shore bombardments.

OT a little, but I have heard of tanks firing their main guns at attack helicopters. Could be effective against a TOW platform.

5 inch guns which were destroyer main guns and secondary on other vessels were dual purposes. Were some 8 inch guns developed in this fashion as well? One of the refits on the British Tribal class destroyers to to change the main guns from a single purpose to a multipurpose role. In some all were changed and others only certain turrets were changed.

Mike T.

The only case I recall reading about of a ship firing her main batteries at attacking Japanese aircraft was at Midway. In Walter Lord's "Incredible Victory" he wrote about one of Yorktown's escorting cruisers firing her 8" battery at low flying Kates.

I am not an expert on AA matters, but when it came to knocking down planes in WW II, it wasn't "size matters" but "weight matters," in this case throw weight, i.e., the total weight of all anti-aircraft projectiles on a given side of a warship that could be put into the air in one minute (considering realistic rates of fire, etc.). Technology helped, sure, with the development of the proximity fuze, but when you consider the AA total throw weight for an Iowa-class battleship was almost 49,000 pounds by wars end - that's a lot of lead.   

Agree with bondoman. 

Sounds like maybe some one confused some notes--the Japanese had done some development work on a shotgun shell-like AA around for the 18" guns.  I want to remember that firing those shells basically scrapped the liners from tearing up the rifling.

There is a reason those guns are called naval rifles.  They are designed to lob a shell at great velocity a great distance.  I'd wager even the 14" rifles would not depress, even "on the roll" enough to get  a shell in the water closer than 3-4 miles.  And that, while risking a squib by short charging the gun.

And, even if you did, those shells are going to be supersonic still, they'd likely hit the water and ricochet right off, not the sort of thing to generate good feelings among the rest of the battle group.

Source, please. I'd discount that. First of all those big rifles took time to lay and fire, plus they were set for a ballistic trajectory. Others would know, but I would guess the minimum range to drop a shell in the water would be at least a couple of miles away.Plus, that attack was a dive profile to hit the deck at a high angle.

Fire control is the answer, I'm sure. I don't know much about it, but I did learn that, while modeling CA 38, the communication trunk from the director to the fire control center was heavily armored.

I have read in a couple of historical books that even the 14" and 16" Main Batteries of the BBs were used against kamakazes.  I don't know how true, but the books were non-fiction.  The Main Batteries would fire into the water just in front of a kamakaze and let it fly into the resulting wall of water.  The plane would disappear without a trace, sucked under when the wall collapsed.  Supposedly several kamakaze planes were downed in this fashion.