.50 cal machine guns vs 20 mm autocannons on US aircraft

[tomo pauk]

The aircraft that is shoot at don't care about muzzle enegrgy, what he cares is the damage he is about to receive. A bullet that has, say, 20% more muzzle energy is bound to make a hole in aircraft skinning, slightly better than a the bullet with lower muzzle energy. If a weapon system indeed 'spits' more energy than another system, but the effect on target is smaller, that there is no point in boasting with that.
I'll concur that 37mm shell was far heavier than 23mm, but they were both fired at same velocity, so the disparity in trajectories to 300-400 yds ought to be minimal. I don't see why should be hit by 37mm, 400 rps gun, regarded as remote possibility.

 

[Shortround6]

For Panther: 102g shell x 4 cannons x 11 rps = 4,49 kg per plane per second. Sabre throws 1/4 more mass, but Panther fires shells, not ball. Advantage Panther, that carries 200 kg of guns vs. 180 kg of Sabre.

Part of this superiority of the F-86's armament over the Panther's armament comes from using the wrong numbers. If the Panther used M3 20mm cannon it was using ammunition with 128-130 gram projectiles. The 102 Gram projectiles were usually used in the M-24 gun. the M3 used conventionally primed ammunition while the M24 used electrically primed ammunition so the ammo was not actually interchangeable. The M3's cycle rate is given as 720, 750 and 700-800rpm depending on source. At 720 rpm it is 12 rounds per second. 128gm shell X 4 cannon X 12 rps is 6.14kg per second vs 43 gm projectile X 6 guns X 20rps is 5.16kg per second. About a 19% advantage for the Panther using numbers in the low part of the range and not the absolute highest quoted.

Muzzle energy (perhaps the worst way to compare firepower=target effect, although a good way of comparing gun efficiency, they are not the same thing) has the short barreled Hispanos at about 46,900 joules per round or 2,251,200 per second for 48 shots. For the .50 cal using M8 API ammo the ME is 17,030 per shot or 2,043,600. about a 10% advantage for the Panther.

Each round of .50 cal M8 API has about 1 gram of incendiary material. If the belts are loaded exclusively with the M8 API that is 120 grams of chemical per second. (the 125 rps requires all the guns to cycle at 1250rpm which is a bit higher than most sources give) A 20mm Hispano round could carry about 10 grams of HE/incendiary per projectile, even if the belts were loaded 50/50 with HE and solid shot that is 240 grams of chemical per second. Major advantage to the Panther battery.

With 190 rounds per gun and a 12rps firing rate the Panther had 15.8 seconds of firing time compared to the F-86s 13.35seconds. 18% advantage Panther.

weight of guns and ammo of the F-86 is 353kg. Weight of the Panthers guns and ammo is 363 kg. F-86 wins this one by under 3%.

Only real advantage for the F-86 is rate of fire and hit probability.

Trajectory and time of flight for any practical range ( 600yds or under) is not enough different to get excited about.

 

[davparlr]

The aircraft that is shoot at don't care about muzzle enegrgy, what he cares is the damage he is about to receive. A bullet that has, say, 20% more muzzle energy is bound to make a hole in aircraft skinning, slightly better than a the bullet with lower muzzle energy. If a weapon system indeed 'spits' more energy than another system, but the effect on target is smaller, that there is no point in boasting with that.

Energy transferred to the target is what matters which is also true with all weapons. Weapon fire over time of the Sabre starts out at a higher energy level than the Mig, but it may dissipate faster, or maybe slower. A lot depends on the aerodynamics of the projectile. I am sure someone out there knows.

I'll concur that 37mm shell was far heavier than 23mm, but they were both fired at same velocity, so the disparity in trajectories to 300-400 yds ought to be minimal. I don't see why should be hit by 37mm, 400 rps gun, regarded as remote possibility.

Probability of one hit of the 37mm with a 5% hit probability per projectile is 30%. For hit by the 23mm it is 75%. For both combined is 83%. Maybe not remote but certainly not likely.

 

[Shortround6]

Without having terminal velocity, this is all an approximation. However, I think it does show the power of the six M-3 machine guns and why the AF kept them. Here is another way of looking at it. I have never heard the P-47 being under gunned. You can take the P-47 armament, add 600 rounds per minute, put it on the center line (I read somewhere the Germans thought one gun on the center line was worth two in the wings) and you can get a feel for what was coming out of the nose of a F-86.

take a Hawker Tempest ( usually not considered under gunned), add 480-600rpm (almost a 5th gun) and put it on the center line and that is what is coming out the front of a Panther or could have been coming out the front of a Saber.

 

[davparlr]

take a Hawker Tempest ( usually not considered under gunned), add 480-600rpm (almost a 5th gun) and put it on the center line and that is what is coming out the front of a Panther or could have been coming out the front of a Saber.

Which would apparently make it just about equal in kill probability to the M-3 armed version of the Sabre.

both of these configurations offered a significant upgrade in fire power over the standard US fighter armament in WWII. The next significant improvement came with the M-39, and, to a lesser extent, the Colt Mk12.

 

[Glider]

Forgive me if I am losing the logic here but if the

Sabre M3 firing 20 rps x 6 = 120 rps. Multiply 43 g per round gives you 5.16 kg per sec
Tempest, Seahawk, Meteor, Vampire etc 4 x Hispano V 12.5 rps x 4 = 50 rps, Multiply 129 g per round gives you 6.45 kg per second

How does this give the F86 more firepower?

I must be missing something, any pointers welcome

PS I am ignoring the much higher HE content of the 20mm which would add considerably to the difference

 

[Glider]

I found this and its pretty good


View: https://www.youtube.com/watch?v=vQL9Kxxd88s

 

[Shortround6]

The 2 basic areas of disagreement are; 1. that the .50 armament combination will hit more often and that the higher number of weaker hits are superior to fewer harder hits. 2. that the Browning offered high firepower for installed weight.

AS far as the latter goes the Russian 12.7mm UB machine gun fired slightly more powerful ammunition at a slightly higher rate of fire for a bit less weight. on a power to weight ratio the Russian gun was over 30% more "efficient" than the Browning.

Since the weight of the installed armament affects the performance of the plane (indeed, the gun armament of a WW II fighter for air to air combat was it's "payload") have a not very efficient main gun imposes penalties aside from just (or instead of) firepower considerations.

 

[Glider]

So to boil it down further (Using Tony Williams details)

0.50 has 2% of Projectile as HE or equivalent and 20mm Hispano 8.8% of the projectile

Given a 5 to 12 ratio (shots per second 6 x 0.5 M3 vs 4 x 20 Hispano V)

This will give you 103 gms of HE for the M3 and 567 gms of HE for the Hispano V which is approx 550% more for the Hispano.

The MV isn't that different but the M3 is going to hit more often however a good percentage of those shots are going to go straight through unless there is something substantial in the way, whereas the 20mm is going to do damage wherever it hits.

Also the longer the range the less the effectiveness of the MV and the greater the reliance on the explosive power of the shell. I don't know the actual ballistics for these weapons but generally they are better for the larger shell so any benefit of the higher MV of the 0.5 will be soon reduced if not lost all together.

Finally its worth considering if the M3 was so effective why did the USAF change?

Does that sum it up?

 

[fastmongrel]

Seems to me the main virtues of the 0.5 Browning, higher rate of fire and a higher rate of hits (with a lighter less effective round) are the exact same points used to criticise the RAF 8 x 303 Brownings.

Not comparing the .303 to the .50 of course just wondering why its the same arguments used for the .50 and against .303 when they are being compared to competing heavier weapons.

 

[Edgar Brooks]

Not comparing the .303 to the .50 of course just wondering why its the same arguments used for the .50 and against .303 when they are being compared to competing heavier weapons.

A lot depends on whether you know why the Air Ministry stayed with the .303", rather than the .5" (which Leigh-Mallory was pushing for in 1941.) It had nothing to do with weight of shot, but everything to do with numbers. In ballistics tests, it was found that the .5" round was no better at penetrating German armour plate than the .303", and, as it went through the fuselage skin, it was just as liable to tumble as the smaller round.
Since the average pilot was not very good at deflection shooting (Johnson was an exception, since he regularly shot wildfowl, so "leading off" was second-nature to him,) it was felt that 4 x .303", at a faster rate of fire, gave a better chance of disabling the enemy pilot than 2 slower-firing weapons. When we brought in the gyro gunsight, shooting improved markedly.

 

[Vincenzo]

on british comparisono fo .5 and .303 i'm not sure remember right, as i remember .5 was yes valuted non enoguh powerfull but not same of .303

 

[Shortround6]

The "state of the art" of aircraft armament was constantly evolving during the 30s and 40s. And with the constantly evolving (increasing) engine power heavier armament could often be fitted. This changed what the "IDEAL" armament could be. The Spitfire I carried under 400lbs of guns and ammo, (254lbs of guns and 160lbs of ammo). Such a weight of allowance would cover TWO .50 cal guns with around 450rounds apiece or FOUR .50cal guns with 110-130rounds apiece. Neither is a particularly good choice. If the armament weight allowance goes to 600lbs then the choice to keep the .303 gets tougher. Four .50 cal can be used with a good supply of ammo. Four 20mm Hispano guns weigh just under 600lbs WITHOUT ammo so they are not a valid choice at this weight allowance. going to 900lbs means Six .50cal guns with good ammo or four 20mm guns with about 120rounds apiece. Going to 1100lbs means Six .50s with lots of ammo or eight .50s with under 250rounds each or four 20mm Hispano guns with 190-210 rounds each.

a good part of the choice depends depends on how much weight you can devote to the armament and what models of which guns were available at the time. A Brewster Buffalo with a pair of Drum fed Hispanos wouldn't have accomplished much more than the what they did with the historic armament.

 

[Shortround6]

Part of this is timing. When the British made their comparison the Browning .50 had a rate of fire of 600rpm at best, not 800-850. Another point was ammunition. How much good incendiary was around for either weapon? Using ball ammo the .50 just punched bigger holes in sheet metal (or fabric) if it didn't hit anything vital. and against vital things ( engine, pilot, radiators, etc) the .303 did a pretty good job since nobody had armor at that time. The .50 could bust up structure better and perhaps burst fuel tanks (split seams?) better but with 1/5 or less of the bullets fired PER WEIGHT OF GUNS INSTALLED, the trade didn't look good.

When the .50 went to 800-850rpm for the same weight and better ammo was introduced that combined with the increase in protection that the .50 could defeat the .303 (or any rifle caliber machine gun) really faded. That doesn't mean that the .50 could not be pushed aside in turn when allowable armament weight ( and bigger, tougher targets) allowed/called for bigger caliber guns.

 

[davparlr]

Part of this superiority of the F-86's armament over the Panther's armament comes from using the wrong numbers. If the Panther used M3 20mm cannon it was using ammunition with 128-130 gram projectiles. The 102 Gram projectiles were usually used in the M-24 gun. the M3 used conventionally primed ammunition while the M24 used electrically primed ammunition so the ammo was not actually interchangeable. The M3's cycle rate is given as 720, 750 and 700-800rpm depending on source. At 720 rpm it is 12 rounds per second. 128gm shell X 4 cannon X 12 rps is 6.14kg per second vs 43 gm projectile X 6 guns X 20rps is 5.16kg per second. About a 19% advantage for the Panther using numbers in the low part of the range and not the absolute highest quoted.

I did not use muzzle energy in comparing the F9F to the Sabre, but rather the Navy's published assessment of the effectivity of the 20 mm round to the 50 cal. Of course this is a WW2 round comparison and if the Navy used a different one in Korea, which I suspect they didn't, the conclusion would be askew. I did not do the energy analysis since I assumed the Navy had more knowledgeable engineers and better test equipment, especially since I have none, and did a much better job than I could ever do analyzing the various armaments.

weight of guns and ammo of the F-86 is 353kg. Weight of the Panthers guns and ammo is 363 kg. F-86 wins this one by under 3%.

Weight difference could add ammo, maybe close to a second of fire.

Only real advantage for the F-86 is rate of fire and hit probability.

And an advantage in probability of kill, if probability of a hit is over 5%. The F9F has an advantage when probability of hit is 5% or less. Of course one has to believe the Navy knew what it was doing when accessing its 20 mm, and if the Navy round used in Korea was the same as that assessed.

So, since I based my assessment of effectiveness of the F-86 vs F9F on Navy data and probability of hits, my position doesn't change, and that is that they were basically equal and the 20 mm would not add much, if any, better capability to the F-86. However, since I did use energy comparisons with the Mig, I need to recalculate because the .50 weight I used was wrong. I used a posted number and did not cross check.

Trajectory and time of flight for any practical range ( 600yds or under) is not enough different to get excited about.

Since I assume the F9F has a similar radar ranging gun sight as the F-86, I didn't think any drop in trajectory would affect probability of hit.

 

[davparlr]

Forgive me if I am losing the logic here but if the

Sabre M3 firing 20 rps x 6 = 120 rps. Multiply 43 g per round gives you 5.16 kg per sec
Tempest, Seahawk, Meteor, Vampire etc 4 x Hispano V 12.5 rps x 4 = 50 rps, Multiply 129 g per round gives you 6.45 kg per second

How does this give the F86 more firepower?



I must be missing something, any pointers welcome

PS I am ignoring the much higher HE content of the 20mm which would add considerably to the difference

My argument quickly. Commander J.P. Monroe, head of the US Navy Armament Branch, in the "Report of Joint Fighter Conference", Oct. 1944, stated that, in horsepower, one 20 mm was equivalent to three 50 cals. He also stated that, in kinetic energy, and at 500 yards, one 20mm is equal to two and one half 50 cals., which seems to imply that the 20mm loses energy faster than the 50. I am sure this is based on the M2 cannon or the HS II.

Comparing the ratio, one 20 to three 50s, and calculating the probability of hits of a one second burst and based on various probability of strikes by a single projectile, I arrived at this data.

At 2% probability of a hit by a single projectile, the F9F will have a 25% chance of two rounds striking the target, the F-86 will have four hits at a similar 25% rate. The F9F has an advantage at this hit probability. It will destroy the target slightly faster than the F-86

At 5%, the F9F will have a 69% chance of two or more rounds striking the target, the F-86 will have five hits at a slightly better probability of 75%. The Probability of kill for the two aircraft for a one second burst is about the same.

At 10%, the F9F will have a 96% chance of two or more rounds striking the target, the F-86 will have seven hits at a probability of 97%. The probability of a kill is now in the favor of the F-86 and it will destroy the target before the F9F. This will continue to improve as probability of a single projectile hitting goes up, eg, aircraft gets closer.

As a results of this analysis, it is my opinion that the armament battery of the 50 cal F-86 and the 20 mm F9F were basically awash in kill effectivity with only slight variance with changes in aiming accuracy, with the F9F slightly more effective at longer distance, but losing that edge as the distance closes. This is also assuming the gun sights are similar in performance.

 

[davparlr]

Finally its worth considering if the M3 was so effective why did the USAF change?

Does that sum it up?

The AF did not change the F-86 until the M-39 cannon came. The M-39, firing at 1500 r/m and higher muzzle velocity, was MUCH more powerful than the M2 cannon. There also was no comparison to the firepower of M39 armed F-86 and the 50 cal. version.

 

[Glider]

Dave
I have looked at this and have a few questions, any observations would be welcome

Actually no, the projectiles hitting the target and the damage they do is what counts. If we look at an individual event, in this case a timed burst of fire e.g. one second, the important factors are probability of a strike, which is the probability of a strike per projectile calculated with the number of projectiles fired, and probability of damage given a strike, in this case the 20mm being three times more effective than the .50 cal
Here is a repeat of my post on another thread comparing the F-86 to the F9F in firepower, reformatted.

I did run a few simple probability calculations on probability of number of strikes given the probability of a strike for 47 r/sec (F9F) vs.125 r/sec (F-86). This is for a one second burst. Two 20mm rounds are used as a reference.

For 2% probability of a strike per projectile:
Out of 47 attempts, the F9F has a 24% probability of 2 or more 20 mm rounds hitting.
Out of 125 attempts, the F-86 will have 4 or more 50 cal rounds hitting (24%).
For 5% probability of a strike per projectile:
Out of 47 attempts the F9F has a 69% probability of 2 or more rounds hitting.
Out of 125 attempts, For slightly better probability, the F-86 will have 5 or more rounds hitting (75%).
For 10% probability of a strike per projectile:
Out of 47 attempts the F9F has a 96% probability of 2 or more rounds hitting.
Out of 125 attempts, the F-86 will have 7 rounds hitting (97%).

Obviously, the more round fired the higher the probability of hits. As shown here, for increasing probability of hits, the F-86 will deliver more hits, from 2x at 2% probability of a hit to 3.5x at 10%. As the planes get closer, or the pilot more accurate, or the aircraft more stable, etc, the advantage moves in the F-86's direction. As the planes move farther apart, the advantage moves to the 20mm. However, for any distance, the probability of equal hits always falls in favor to the F-86.
Given the Navy analysis of one 20mm equal three .50s, at about 5% probability of strike (five projectiles hitting out of one hundred), the F9F and F-86 are roughly equal in fire power, below 5% probability of strike, the F9F delivers more damage, above that, the F-86 is more effective, at least according to probability.

It also must be noted here that one poster pointed out that the armament of the F-86 is lighter than the F9F, although a couple of seconds less in firing time. Equal being equal, both are probably equal in weight per firepower. I did not check his numbers.

It is apparent to me that the six M-3 machine gun battery on the F-86 was reasonably equal in effectiveness and weight to the four M-2 cannon on the F9F, and for the Korean War, was as state-of-the art as the 20 mms, not just a "tweaked", old gun. I think the claim that the Korean War F-86 was under-gunned is a myth.

The comment that one 20mm was equal to 3 x 0.5 was a general statement applying to the weapon, not one 20mm hit was equal to 3 x 0.5 hits. My understanding would be that he additional chance of obtaining a hit would have been factored into the equation. To put it another way the additonal chance of a hit would be more than 3 to 1 in the F86 favour due to the larger number of projectiles fired but the impact of a 20mm hit would be significantly higher.

To compare the rounds
one 20mm projectile weighs 110 gm and has an HE/I content of 11% giving 12 gms of explosive per round
one 0.5 mm projectile weighs 43 gm and has an HE/I conent of 2% giving 0.86 gms of explosive per round
Clearly this is a huge advantage to the 20mm.

Applying this to the percentage chance of a hit as you posted at 10% which was the least favourable result for the Panther

For 10% probability of a strike per projectile:
Out of 47 attempts the F9F has a 96% probability of 2 or more rounds hitting.
Out of 125 attempts, the F-86 will have 7 rounds hitting (97%).

The Panther has 2 x 12 gms of explosive on the target = 24 Gms
The F86 has 7 x 0.86 gms of explosive on the target = 6.02 gms
Basically this is still a 400% advantage to the Panther.

I have ignored the heavier impact of the 20mm due to its larger size and MV which would give it better penetration. I have also ignored the better ballistics of the 20mm as the radar ranging would probably have allowed for that.

 

[Glider]

Our postings crossed I am now looking at your previous one

 

[Glider]

Cancel my previous I had the wrong 20mm sorry everyone for any confusion. Will now redo the stats.