P-40 vs. ME-109

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"Riddled" is hardly the right term.

The Hispanos went through a relatively protracted pre-war development process with the French Air Force, and then a somewhat more truncated development with the RAF, but, after initial failures in combat trials during the Battle of Britain, they were considered a very effective and reliable weapon.

The Hispano Mk I, which displayed much problem with jamming was quickly replaced by the more reliable Mk II, and used as the RAF's basic fighter armament from 1941 onwards.

The problems with the Mk I were in several areas. Lightly struck caps caused problems with misfires, the canted over installation, particularly in the Spitfire, combined with a less than satisfactory feed mechanism for the 60 round snail magazine, also lead to jams. Another problem with the Mk I was again tied to the installation, was the wing mountings were initially to light to handle the recoil. Wing flexing was also a problem which lead to jamming. Both of these were tied to the Mk I's origin, in the form of the French HS 404 'moteur cannon' and the differing installation requirements that such a gun had.

The Hispano Mk II sorted out many of these problems, particularly the magazine feed and modifications to the chamber, firing pin and extractor spring, to reduce mis-fires and poor cartridge ejection.

In mid 1942, the Hispano Mk II was tested against the US 20mm M1 and AN-M2, firing 5,000 rounds. The RAF gun averaged about 1 stoppage in 275 rounds. The three US guns average 1 stoppage every 60, 39, and 27 rounds respectively, and none of them were able to complete the full 5,000 round test before destructive failure.

By 1943, testing showed reliability of US 20mm cannon had improved, but the RAF never used any of their imported US 20mms in combat. Even the 20 mms coverted to AAA guns went straight into storage.
 

Tell me what the angle for each gun's bore site is in relation to the line of site?
Bore site charts are used to set convergences not compare trajectories. You need to fire both guns at the same angles to make this comparison relevant. Its not really the best source for what your trying to show.

I understand altitude and pressure density, but when your bullet is traveling at 2-3 mach, air is still pretty freckin dense.

The 20mm is over a quarter inch wider than the 50 cal, so i'm trying to figure how you would think their coeficient would be similar.

The .50 M2 bullet weighed 46g giving an SDR of 0.406 (therefore) BC = .54
The 20mm Hispano weighed 130g giving an SDR of 0.462 (therefore) BC = .31

COMBATSIM.COM ARCHIVE FORUM : Ballistic coefficients
This guy explains what all the numbers mean better than i can.

But basically what this means is the 50 caliber is nearly 42% more efficient at holding its velocity than the 20mm was.
I hardly consider that similar.

All else being equal, bullets that have the same BC would follow the same trajectory path. You might notice the 7.92mm had a BC of .30


And the nonsense about the Spitfire was a just a joke, mate.

Bill
 
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billswagger said:
But basically what this means is the 50 caliber is nearly 42% more efficient at holding its velocity than the 20mm was.
I hardly consider that similar.
l
Click to expand...

Would that make the .50 caliber superior at armor-penetration at ranges of over 200 yards?
 
billswagger said:
But basically what this means is the 50 caliber is nearly 42% more efficient at holding its velocity than the 20mm was.
I hardly consider that similar.
Click to expand...
42% gives a false idea of accuracy as one half of the formula is "guesstimated". Only a small error in this guesstimation will lead to very different results. Academic approaches are nice and all but the empirical results as indicated by the bore sighting chart simply show that for all practical purposes there is no difference in effective range. As mentioned the trajectory differences are below normal ammo and gun induced dispersion.
 
Demetrious said:
Would that make the .50 caliber superior at armor-penetration at ranges of over 200 yards?
Click to expand...

For the purposes of WW2, it depends on the rounds used. HE rounds explode on impact so armor penetration is not really their intended purpose. AP 20mm was shown to be more consistent and more effective up to 400 yards.


Armor penetration in mm


================
Browning 50 cal
================

APM1(RA/40) :

20 @ 200 yards
18 @ 400 yards
16 @ 600 yards

APM2

22 @ 200 yards
19 @ 550 yards
10 @ 1300 yards

(SLAP) modern M2 (light armor piercing, doesn't apply to WW2)

34 @ 550 yards
23 @ 1300 yards

=============================
20mm Hispano
=============================
Ball Mk 1

12 @ 200 yards
10 @ 400 yards

HE Mk 1

8 @ 200 yards


AP MkII.Z

27 @ 200 yards
24 @ 400 yards


The 20mm being a heavier round also would show more consistency at various angles. The steeper the angle, the less effective 50 caliber becomes by comparison.




Bill
 
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The boresite chart simply indicates the convergence range. The guns are fired at different angles so that corresponding arc meets in the convergence zone. Its good information but doesn't indicate effective ranges for either round only that they can be paired and converged in a way illustrated on the chart.

Indeed its splitting hairs at 200 yards, but at 400mph and turning the differences in ballistic properties are augmented.
I don't know how accurate Tony Williams guestimate is, but he is an ammo expert and written several articles as well as a book.
Methods used to indicate form are not far off from his method, and his numbers are valid and consistent with other data.




Find the 20mm Hispano round.

Hint: its the one with the blunt tip.


more info:

This guy did 4 months of research and explains his methodology.
http://members.cox.net/rg_lunatic/gunpage/index.htm

The charts indicate velocity at different ranges and the blue squares indicated mach 1.5 speed. Simply put, the bullet experiences higher amounts of drag the longer it travels above the speed of sound, in turn most speed loss occurs in the first few hundred meters. Speed of sound changes with altitude, so these are sea level indicators.

His chart says the 20mm slows to about 705m/s at 250m, where the 50 caliber slows to 695m/s at 400m. This indicates a loss of over 150m/s from the distance to the muzzle. (best case)

150 m/s = about 335 mph.

i'm sure you can see where this is headed when planes travel from 200-400mph in a combat scenario. These figure don't factor in the speeds at which the plane firing is going. It would only complicate matters, but the point is illustrated further.

http://members.cox.net/rg_lunatic/gunpage/Ballistic_Methodology.htm
His methods.
Here he points to historical data which suggests the 20mm retains 48 percent less velocity than the 50 caliber at 600m.


Bill
 
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Duh of course they are fired at different angles. The point is that the difference in trajectory is MINIMAL, you continue to ignore that. The chart you provide, if accurate, indicates that the difference in time to reach x, is less than 10% for all x below 500m. Anything beyond that range is unrealistic to achieve with a decent hit probability given the combat conditions and the crude gunsights, especially if the target is a single engined fighter. And you can quit pointing to the blunt nose of the 20mm ammo. We all know that and the web site you quote "guesstimates" kind of like I did that the form factor is less important for the ballistic performance when compared to the sectional density. The qualities of having a good form factor apparently are not as important for aircraft cannons, which would also explain why virtually all WW2 era aircraft cannon designs didn't give that much attention even though the manufacturers that built them were very well able to build streamlined bullets (Germany, Russia, France, UK...). Even among modern cannons there are many (like the M61) with very "dirty" shaped ammunition.

It's obvious you have your mind dead set on the .50, so I will just leave it at that. But I would be curious: There are a number of USAAF fighters that were equipped with 20mm Hispanos, most notably the P-38. Was there ever a report that P-38 pilots complained about the lack of range of that cannon or its lack of felt accuracy in a turn fight (reliability issues aside) when compared to the M2? Imo the M2 had its advantages even in the air-to-air role, primarily as a defensive weapon for bombers where the range advantage over German cannons was more important than the destructiveness or efficiency. The simple fact that a German fighter pilot was usually always under fire upon starting his attack run matters.

As an offensive gun however it was just acceptable. I don't believe the USAAF ever thought it to be perfect for its task as some people here argue or else they would not have multiple projects to get a 20 mm to work, going as far as trying to copy the MG151.
 
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This discussion has been had before and it seems to me that the various advocates for the aerial cannons and the 50 BMG are mostly talking past one another. To me, any attempt to prove that the 50 BMG was NOT inferior to the 20 mm or for that matter the 37 mm or 30 mm if all guns firing those projectiles were roughly equal in reliability, is futile. Those cannon rounds were more destructive than the 50 BMG. The MGs mainly relied on kinetic energy or sometime incendiary effect for their destructiveness and when the cannon shell exploded it was more destructive. However, the 50 BMG was a very destructive bullet because of it mass and velocity and many many EA were destroyed by the 50 BMG. Someone earlier made the point though that the German fighters and British fighters armed with cannon did not go on long escort missions because they did not have the range. They also were being used often to shoot down four engined heavy bombers or well armored Russian ground support bombers, or in the case of the British fighters the only alternative to the cannon was the rifle caliber guns. Since those fighters were in the air only a short time they did not need a lot of ammo. The fact is that hits in fighter versus fighter combat were hard to obtain and the large number of guns carried by US fighters and the high rates of fire made hits a little easier to obtain and the long firing times, (compared to cannon equipped fighters) meant that US fighters on long escort missions could still contniue to be armed when a cannon equipped fighter would have been out of ammo. Perhaps the best armed US fighter was the few F6Fs that carried two, hopefully, reliable 20 mm cannon with 225 rounds for each gun and four 50 BMGs with 400 round each. When the 20
mms were exhausted he still had four effective guns with some ammo left. However that F6F had a big thick wing to carry all those guns and ammo and one wonders how much it's performance was degraded by the additional weight.

Was the 20 mm round more destructive than the 50 BMG? YES
Could the US fighters carry more guns and more ammo if they were 50 cals instead of 20 mms? YES
Did the more numerous 50 cals with a higher ROF enable the US fighters to get more hits? YES
Did the longer firing times of the US fighters because of being equipped with 50 cals enable them to still be lethal on long missions? YES

Those seem to be the salient and unarguable points.
 

The angle of the bore doesn't really matter in this case does it?

I am not trying to prove that the 20mm was better or equal to the .50 in a purely theoretical case. I am trying to prove that at normal air combat ranges the .50 didn't have enough of an advantage to get all worked up about. Unpleasant as that may be for some .50 cal fans.

since the chart shows that up until 500yds the 20mm trajectory can be made to match the .50 cal trajectory within 3in or less I would say the chart does help show what I am talking about.

It certainly is a lot more on point than your statement from post #219

"It was also determined that cannons (not sure of the caliber) had an effective range of 250y, where 50 caliber had an effecitve range of 850y."

or from #224

"Shots of 50 caliber remained inside the site ring for 850yards. Shots of cannon fire remained inside the site ring for 250yards."

billswagger said:
The 20mm is over a quarter inch wider than the 50 cal, so i'm trying to figure how you would think their coeficient would be similar.
Click to expand...

Not sure what you mean by this one. For lead round balls the ballistic co-efficient goes up with an increase in caliber. Same with any similarly shaped projectile, as in different diameters but similar shapes including length to dia. ratio, the larger diameter projectile will always have a higher BC.

I have a lot of respect for Mr. Williams but in this case he is (and admits) he is using estimates. For instance he uses the same form factor for the German 20mm and the Hispano. While there may not be a huge difference there is a difference:

http://www.quarry.nildram.co.uk/20mm1.jpg

I have some some figures that I am not real happy with but I will give them to you.

Time of flight to 600yds for a .50 cal 753gr/2900fps is 0.72sec, angle of departure is 14 min, remaining velocity is 1950fps. Retained velocity is 67%

Time of flight to 1000yds for a .50 as above is 1.32sec, angle of departure is 30 min, remaining velocity 1575fps. Retained velocity is 54%

For a prewar 20mm cannon with a 2000gr/2750fps round the 600yd time of flight is 0.84sec, angle of departure is 17 minutes, remaining velocity 1650fps. Retained velocity is 60%

For 1000yds the numbers are time of flight 1.71sec, angle of departure 42min and remaining velocity 1210fps. Retained velocity is 44%

Please note that these figures are from "Automatic Arms" by Johnson and Haven except for the percentage of retained velocity which is mine.
While the .50 shows a marked superiority in flight times, angle of elevation and retained velocity at 1000yds the margin of superiority at 600yds is nowhere near as great.

If somebody has better figures please bring them out.

I would note that at 600yds if a .50cal and a 20mm were fired at the same instant the 20mm's 1st shell would arrive hard on the heels of the .50cal's second bullet if free firing and just a bit ahead of a synchronized .50 cal's 2nd bullet.

At distances below 600yds the differences are going to get smaller.


billswagger said:
And the nonsense about the Spitfire was a just a joke, mate.
Click to expand...

Good Joke then, I said it gave me a good laugh.
 


Its obvious you use erroneous conclusions.

Trajectory is minimal? Is the chart to scale? Does it give the angles?
I don't expect you to answer that, I've already admitted its an apples to apples comparison under 300 yards.

Not really trying to drill the point so much as share what i know.

I guess what i was getting at was the 50 calibers ability to maintain velocity at higher speeds, and USAAF recognized this over the 20mm.
Somewhere in the comparison of muzzle velocities and coefficients i was intending to show that the bullet has better effective range. Hopefully what i've shown gets through to you. Effective range is the ability to hit the target and do damage.

As for the bore site chart. I simply disagree about its use to show similar effective range for 50 caliber and 20mm. Your more than welcome to beat me up about it, but it doesn't change the facts about the ballistic behaviors of each weapon.
P-38s had the advantage of the nose mounted armament which made calibration easier. I don't doubt P-38 pilots ever complained about range. With proper trajectory and calibration you could probably get an effective range of 1000yards.
Point is, your gonna have an insane arc. Geez, they could probably set the trajectory of the 50 cal to hit at over 2000 yards. Oh wait, thats called a sniper rifle.
When the target goes into a turn at higher speeds, you'd need to pull more lead and at higher speeds thats where the 50s have a better chance of hitting. The closer the target the less difference it makes.

If you think they have the same effective range, show me something other than a boresite chart from a P-38.




Bill
 
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1 agree
2 but if we take in consideration the more damage of 20 mm the US fighters with 20mm can carry more effective weaponry with same time of firing.
3 yes but the hit of 50 give less damage of hit of 20mm so this indifferent (with just proportion)
4 with same time of firing the US fighter can use 20mm ever if we take in consideration the just proportion (damage delivered to target)
 
Shortround6 said:
The angle of the bore doesn't really matter in this case does it?
)
Click to expand...

If your firing in a straight line at zero mph, probably not much at all. In turns at high speed, i would think ballistic behaviors are gonna tell you a bit more info.

An aircraft moving at 300mph at 10,000ft fires into a headwind. You'd have to have atmospheric conditions to get exact figures but it would make a difference if the coefficient of the 20mm is 40 percent worse.

Your numbers on velocity correlate with most other numbers i've seen which seem to pin the difference in velocity loss at 29 percent for the 50 caliber, and 43 percent for the 20mm. 43-29 = 12 , 12/29 = 48 percent (600m) Ball round data

The faster the plane gets the more distance the bullet needs to travel to the target its shooting. So a shot at 300meters may infact may need to travel through another 75 meters of air to hit a moving target.
You start to see how a bullet that's 40 percent less efficient would start to show at combat speeds and ranges.
You could adjust trajectory for accuracy but it doesn't make up for velocity loss where a tenth of second is enough to make your shot miss by a significant margin.

I can't help think of race cars that travel at 200mph, When they show the lead car as having a 0.10 second lead, and the gap that appears to the trailing car. You could probably fit a Mustang or two between them.

"A round that doesn't hit its target is never effective. "
 
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billswagger said:
You could adjust trajectory for accuracy but it doesn't make up for velocity loss where a tenth of second is enough to make your shot miss by a significant margin.
Click to expand...

Well, lets look this then. At 600yds the 20mm round is .12 seconds behind the .50. Close enough to " a tenth of second"?

But then the second round out of a syncro-ed .50 is the same time behind or more. These guns are fired in bursts after all. Some pilots may have started shooting behind the target and "traversed" (turned tighter) to bring the bullet stream/s through the target and then ahead to get the correct lead. Others may have over lead and then loosened their turn a bit to let the target run into the stream of bullets, Some tried to use tracers to correct aim but that doesn't work so well at 600yds does it? Tracer tells you were you shooting 3/4 of a second ago.

comparing the times it looks like the 20mm may need about 16% more lead than the .50. Of course if you are defection shooting at 600yds you are either very, very good or hoping for a whole lot of luck.

As the range shortens the difference gets smaller. At range "X" (20mm needs 10% more lead) could you really tell if you were leading the target by 66ft rather than 60 ft?

The .50 will show an advantage, but it only shows a big advantage at ranges beyond normal air to air combat ranges that were common in WW II.

As for this "Is the chart to scale? Does it give the angles?"

It doesn't have to be to scale does it?
Since there is a chart that lists the exact below and above line of sight distance for the trajectories in inches for every 50 yards of range out to 500yds.

I have given you angles of elevation for both 600yds and 1000yds. But they may be nominal angles which assume bullet rising and then falling to the same plane as the muzzle of the weapon and not take into account the difference in hight between the sight and the barrel.

Angles for the bore sight chart are useless. barrels will vibrate differently from each other when fired and have different points of impact using the same nominal bore alignment ( as in optical or laser bore sighting) which is why nobody but a fool doesn't test fire a weapon to confirm point of impact in relation to sights. once you have a known point of impact for a barrel you can then bring the barrel up either the "correct" number of minutes or you can use a short range sight in chart (like 1000in) and when the guns point of impact coincides with the proper point on the chart/target you will automatically have the desired arc/trajectory for the sight/ranges desired.
 
Yeah, i agree with what you are saying.

What your still missing is the point that the faster the plane moves the more the bullet needs to travel to get to the target and
you also have more air resistance acting on the coefficients of the bullets.

A test fire from a stationary gun is not likely to show this accurately but the differences in trajectory would probably correlate similarly to speed shot from as it does range.

So it would be apples to apples at 180mph and 200 meters range, but at 400 mph and 300 meters range you might see greeter differences than whats depicted on the chart. (augmentation)

Part of the reason the 50 caliber gets its praise is for its ability to hold speed at higher mach numbers.

I could throw altitude and mach effects into the equation but i think that might be splitting flea hairs.

To digress a bit, i know that an angles fight often involved getting in a snapshot that would do the most amount of damage in the least amount of time. The 20mm is better suited for this but would be limited by rate of fire and firing time.

At higher speeds, and in energy fights, the goal is similar however efficiency of the shot needs to insure it will hit the plane.
At higher speeds, it is not always possible for the fight to develop to a point where the pilot can shoot at closer range.
As you know ammo loads are critical to compensate for deflection shooting.


Bill
 
SR, those are very interesting numbers you have posted. Many thanks. Those numbers raise an interesting question. In a P38, with the one 20mm and the four 50 cals, if the pilot was trying a full deflection shot at 400 yards, (very unlikely) against an EA traveling 350 mph, the rounds from the 50 cals would hit in the same vicinity but the 20mm rounds would hit further away longitudinally. Correct?
 
To get back on topic i found a short read on Google books that goes into the handeling charcteristics of the 109.

Its a decent read because it gives several perspectives and also distinguishes RAF reports from propaganda.

The commonality i see in most reading regarding the 109 is its poor elevator response at higher speeds as well as its decrease rate of roll.
At speeds above 250mph it becomes difficult to fly and maneuver well and dives at 400mph could be difficult to recover from.

The Putnam Aeronautical Review - Google Books

starts with Handling and reads to the next page.


In comparison of the P-40, although under powered at higher altitudes was able to maneuver more effectively at higher speeds.
Increased maneuverability allows for tactical superiority since a broader range of maneuvers can be used.

This is not a full proof approach to what fighter would come out on top, but rather illustrates the apparent disadvantages the 109 had where the P-40 could be successful in a combat scenario between many aircraft.

I don't see how the Thach Weave would not also apply to 109 being that it was particularly successful against the Zero which also suffered in high speed maneuvers.

The short coming of course would be the climb and altitude issue. It just seems tactical advantage would need to be in place before the 109 had the chance to escape and climb to a position of advantage. (many vs many)

While some of the bombing campaigns took place over parts of Italy and Sicily, it was learned that 109s were dispatched on average of about 15 minutes before the bombers got over their targets.
P-40s had the range to fly to the target area ahead of the bombers awaiting for 109s attempting to take off or climb to intercept bombers.

109s attempting to dive away had little maneuverability if being pursued by a faster diving plane, P-40s included.


Bill
 

Depends on the deflection angle and also the speed of the aircraft being shot at. Steeper angle would mean greater separation even at 200 yards, but having pin pointed accuracy with an HE round is not as critical. You only need hit the wing once or twice and the plane will have trouble remaining in the fight.

You also have to couple that with rate of fire.

Deflection shooting at 300-400 yards was quite common on 50 caliber load outs. (20-30 degrees)
In reading combat accounts, a pilot pulling deflection is usually closing at higher rates of speed. You have an aircraft moving at over 400mph toward its target, while the target is slower but banking and/or turning to avoid being hit. The bullet that gets there the fastest wins.

Its really the difference between hitting the nose or hitting the tail. Or hitting a wing and not hitting a wing.
No doubt experience would compensate for any corrections needed to compensate for deflection.

Its apples to apples in the end.


Bill
 
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Bill, if you will notice, I said full deflection, which means the attacker begins to fire at 90 degrees to the target. Only USN trained pilots spent much time in full deflection gunnery because of issues like visibility over the nose, so my question is somewhat academic. However, the P38, unlike most other fighters had good visibility over the nose. The question is only interesting because the P38, like all fighters with all armament closely grouped, had a very good concentration of projectiles. But if one projectile is traveling more slowly than the other four then that concentration would suffer. An example might be that four rounds hit in the cockpit area and the 20mm round might hit further back on the fuselage. The question is how much further back? For a very fine discussion of Aerial Fixed Gunnery and deflection shooting, go to Appendix 2, Lundstrom, "The First Team."
 
If my math skills don't betray me (which they usually do), at 400 metres, full deflection, EA flying at 350mph (563.3 km/h), the 20mm bullets would hit about 4.69 metres aft of the .50 calibre bullets.

I took metres since I'm to lazy to convert the chart into yards.
 
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drgondog said:
You are right, the RAF did not use the aft fuse tank - at least not as far as I know.
Click to expand...
At the moment I only have Gruenhagen's book which gives figures of:

P-51 B/C/D Internal Fuel wing/fuselage tanks 500 miles combat, 1,200 miles ferry
+ 75 gal drop tanks 880 miles combat, 1,830 miles ferry
+110 gal drop tanks 1,000 miles combat, 2,120 miles ferry


The ranges for Mustangs with wing tanks is given as:
Mustang I, P-51, A-36, P-51 A/B/C is 400 miles combat, 900 miles ferry
 
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