Bf-109s and FW190s against B17s

[Shortround6]

I will bow to your operational knowledge. Most books do not mention the feed problems that a lot of US .50 installations had or what was done to solve them, except that mention is often made of using electric motors from B-26 turrets to help fix the feed problems on the P-51B & C.

The "explosive" round mentioned by your father and Henry Brown could well be the M23 incendiary, it did have a lot of problems with prematures and went in and out of production several times between WW II and Korea and manufacture was shifted from plant to plant at least once if not twice in attempts to solve the problem. I don't know if the problems were completely solved by Korea or just reduced enough for service use in a shooting war. I believe there were a few occurrences of the bullets igniting in the barrel.
A standard M8API has 15 grains (0.97grams) of incendiary compound in the tip ahead of the AP core. The M23 had 90 grains (5.83 grams) and was essentially a gilding metal covered steel tube full of incendiary material. It was around 500fpm faster in velocity than standard .50 cal ammo due to the bullet being so much lighter. about 10 grams lighter.

There may have been a explosive bullet, I have never heard of it but there are a lot of things I have not heard of
The M23 existed at the time I think you are referring to, it did have major problems in use similar to what I think you are describing.
What the men in the squadrons called a particular round vs what the official nomenclature was may well differ.

somewhere in the number of .50 cal threads on this sight I believe I posted a set of cross sections of .50 cal bullets including the M23.

 

[stona]

Monroe's comments from Patuxent in full:

"As it is now, we have the 50-cal gun which has reached its peak. The only improvements will be minor. The only good increase is to increase the number of guns. So it seems to be just about the right time to look for a better weapon. There are two possibilities here- the one we have and the one we might get shortly. The one we have is a 20mm gun. I think very highly of it. It is a fact, we have one here, and it is one in hand. It won't do what the 60 will do, but we haven't got the 60, and we won't have it for a year. So we are gradually working into all our aircraft the 20mm gun. To give you some idea of the 50 versus the 20 and dispel a lot of the ideas that have bothered us, I would like to give you a comparison. When somebody goes from four 50s to two 20s, to the layman that means a decrease in fire power. Actually, quite the reverse is true. In the horsepower of the gun, one 20 is equal to three 50 calibers. In the actual rate of fire delivered at the target, one 20 equals three 50s; in kinetic energy at 500 yards, one 20 equals two and one half 50s.
That adds up to four 20s equalling twelve 50 calibres, judged by those standards. Of course you have other advantages of the 20. You have much greater penetration of armor. The 20 will go through 3/4 inch of armor at 500 yards, while the 50 cal. will go through only 0.43. In addition to that you have one more great advantage-that is, you can have longer and more frequent bursts without damage to the gun with the 20 than you can have from the 50 cal. That is important for a strafing airplane, because they are burning up their barrels and ruining their guns on one flight. Sometimes it is long before that one flight is over. They will come down with screaming barrels and get trigger happy, and then all the barrels are gone in one flight. It should not happen in a 20mm. Of course, you have disadvantages. You have a heavier installation, one half as much armament for the same weight . Our standard ammunition in the Navy is 400 rounds in one gun. The Fleet has set up 30 seconds of fire as a minimum requirement for the 50 cal. gun. We can't do that with the 20s, so we give then 200 rounds. The 20 is lethal enough to get far more results out of that 200 rounds than the 50 ever will out of the 400 rounds."

Cheers

Steve

 

[Shortround6]

Could I ask what is the date of the Patuxent statement ?

 

[Greyman]

I believe the change in rate of fire could be achieved by changing just a few parts, including the buffer? and could be done at squadron level.

For what it's worth ...

British Browning .50 in. Gun manual (April 1942):
The speed of the gun, which is approximately 800 rounds per min., can be adjusted by regulating the flow of oil in an oil buffer.

 

[Shortround6]

Thank you.

 

[stona]

Could I ask what is the date of the Patuxent statement ?

The conference ran from 16-23 October 1944

 

[muskeg13]

Too bad this wasn't developed sooner. It's claimed that it makes the .50as effective as a 20mm. Raufoss Mk 211 - Wikipedia

 

[drgondog]

It became VERY clear even to USAF that the day of 50 Cal was at its end for air to air combat at high altitudes. NAA, for GUNVAL, converted 4 F-86E and 6 F-86F with the prototype M39's (IIRC). They lost one to flameout caused by blast gas and several flamed out but were restarted. That said, the limited experience in early 1953 sealed the fate of the M3. Also, IIRC the 6-3 wing replaced the conventional wing with LE Slats, improving speed and turn and climb, but higher landing speeds.

 

[Shortround6]

The statement from the Patuxent conference is helpful but hardly definitive.

It leaves a lot unsaid and uses a rather basic method of comparison between guns. As far as muzzle horsepower goes a 20 gauge shotgun slug .625 oz (273 grains) at 1580fps has less muzzle HP than a .220 Swift 48 grains at just over 4000fps. range and target effect are ignored.

I don't know if it was a result of the conference or the statement at the conference was a summation of what was going on in procurement but the Navy ordered NO new fighters armed with .50 cal guns after the fall/winter of 1944. They took delivery of thousands of aircraft already on order over the next few years but no new fighters or versions were planned with .50 cal guns.

I would also note that the M2A1 gun was starting production at around this time with a cycle rate about 100rpm faster than the M2 but was stopped after 8000 guns were made out of over 33,000 ordered( I have no idea if any actually went over seas) because of the progress on the T25E3 project which was standardized as the 1200rpm M3 in the Spring of 1945. First experimental T25E3 had been fired in July of 1944. We have no idea of which .50 cal gun the Patuxent statement is referring to. Also please note the above mentioned M23 round was in combat trials in the fall/winter of 1944 with rather mixed success.

Getting back to the Germans vs B-17s the German MG 151/20 had about twice the muzzle horsepower of the .50 cal gun and roughly 2/3rds that of the Hispano. It had a cycle rate (750rpm) somewhere between the Hispano (600rpm) and the .50 Browning (750-800)(book rates) and the synchronized guns in the FW 190 wing roots were probably about 10% lower than the "book" numbers.
The three common rounds the Germans used for air combat (others were used for surface targets) were
APHE, 115-117 grams at about 705mps with 4 grams of HE filler.
HEI/T, 113 grams at 705mps with 4.4 grams of he/incendiary material.
Mine shell, 92-95 grams at 800-805mps with 18.6-20 grams of HE. no tracer.

The last is what made the reputation of the MG 151 as a bomber destroyer. However it's light weight and poor ballistic shape meant it lost velocity quickly and while the trajectories/times of flight of the 3 rounds matched fairly well at close ranges the MG 151 was not a long range gun. Also the actual destructive effect of the MG 151 varied considerably with the mix of shells in the belt. Was the mine shell 33% of the load or 60% of the load?

The late 1944 .50 cal was using the M8API of about 43 grams at 880mps with about 1 gram of incendiary material. The .50 retained velocity better than any 20mm projectile and had a significantly shorter time of flight at any but the shortest of ranges.

To compare guns/aircraft another way try comparing the weight of metal delivered per second. A P-47 with eight .50s firing at 720rpm will deliver 4.128 KG of projectiles per second.
A 3 gun FW 190 (one through the prop and two in the wing roots ) will deliver 3.864kg IF the belt is a 1 : 1 : 1 mix. Granted the German fighter is delivering more HE/incendiary.

 

[Peter Gunn]

RE: Project Gunval, as I recall, there was an NAA engineer that solved the issue of flame-outs on the cannon armed Sabre by adding a small horseshoe shaped apparatus or clip at the end of the gun trough. I believe it broke up the gun gas and channeled or deflected it away from the intake. I could be wrong but I believe that solved the issue.

Initially I think they tried a selector in the cockpit to fire only a pair of the guns at a time but that didn't work so well either, hence the horseshoe thing.

Also as a side note, those crazy Aussies stuck a pair of 30mm Aden's in their Sabres, on on each side, but I have no information if they had similar flame-out problems as the Gunval Sabres did.

 

[GregP]

Mass delivered per second is just one of the factors in the Soviet "quality Factor" variable. I believe it takes into account the mass per second delivered, the kinetic energy, the explosive energy, (all the preceding add to it) and the weight of the gun (detracts from the Q factor). I may have left something out.

Google "The great Fighter Gun Debate" and read the article. If you create a spreadsheet to duplicate the values shown, you have the relationships. It seems like a very GOOD measure of a firearm, at least to me.

 

[stona]

Google "The great Fighter Gun Debate" and read the article. If you create a spreadsheet to duplicate the values shown, you have the relationships. It seems like a very GOOD measure of a firearm, at least to me.

I think you mean something like the table(s) to be found here

WORLD WAR 2 FIGHTER GUN EFFECTIVENESS

Cheers

Steve

 

[GregP]

Actually no, but, that IS a nice table of characteristics.

More like here: The WWII Fighter Gun Debate: Gun Tables . The Soviet Quality Factor is shown as "Q." When you do the spreadsheet and account for consistent units, the numbers come out quite well. A LOT of thought went into the Q factor, and it seems like an ideal metric for gun effectiveness to me, as an engineer.

Many things can be quantified in various ways. The Q calculation takes into account all of the important characteristics of any weapon firing projectiles from an aircraft. I say "from an aircraft," because the gun weight hurts the Q factor. If you were looking at a gun for a tank or a ship, weight might NOT be a factor at all and, for a tank, gun size would be much more of a factor than for, say, a ship. So, detracting from the score of the metric for a characteristic depends largely upon the intended use of the weapon.

 

[Clayton Magnet]

A P-47 with eight .50s firing at 720rpm will deliver 4.128 KG of projectiles per second.
A 3 gun FW 190 (one through the prop and two in the wing roots ) will deliver 3.864kg

What is the total weight of eight M2's plus ammunition as compared to the three MG151/20's plus ammunition? The 8 machine guns may throw as much mass down range, but the performance penalty imparted to the aircraft would make that a relatively poor arrangement.

 

[Shortround6]

The weight is a disadvantage of the .50 cal gun. It is one of the reasons the P-47 was as large as it was. However there are at least two other reasons so the entire difference cannot be charged up to just the .50 cal battery.
I would also note that the P-47 battery could fire for for over 30 seconds IF the ammo trays were full. They often were not in order to carry under wing loads/drop tanks but even the reduced capacity was good for 20 seconds or so.
IF the wing root guns on the FW 190 have 200rpg they are good for about 18 seconds. Sources differ on capacity and actual rate of fire.

Once you had the P-47 at the size it was taking out guns/ammo doesn't do much for performance. More change in climb that level speed or turn.

 

[Clayton Magnet]

I think the Thunderbolt would have been better served by 4 Hispano cannons, but that is another thread, and the M2's did the job adequately. If the USAAF faced fleets of bombers like every other major combatant did, perhaps that would have accelerated the development of an American produced cannon. I seem to remember something about the US trying to develop a copy of the MG151/15, but nothing came of it.
Then perhaps they would not have gone into Korea still armed with .50's

 

[Shortround6]

Please see: Welcome to Culver's Shooting Page

The US had literally dozens of gun programs going on during WWII. A wide variety of fast firing .50s. A wide selection of .60 cal guns and 20mm guns. Not all calibers stayed with one type cartridge.

Select Volume 3A and start on page 4 for the.50 cal guns. A number of post war guns are included but the 40mm guns start on page 39.

 

[pbehn]

I believe the British settled on 4 x 20mm canon for fighters sometime in late 1940/41. the Hurricane MkII, Mustang Typhoon and Tempest all had 4 x 20mm canon as did the post war Sea Fury. The exception was the Spitfire but this was simply because the canon require heating and ducting hot air to 4 guns. For the Hurricane Mk II it was clear that it couldnt compete with the Bf 109f in 1941 but it continued to be produced until 1944 not as a fighter but a ground attack aircraft

 

[Shortround6]

..........Then perhaps they would not have gone into Korea still armed with .50's

as has been noted the USAAF went into Korea with 1200rpm M3 .50cal guns instead of the 800rpm (nominal) M2 .50 cal guns of WW II.
They were also firing the M23 incendiary round at 1036m/s muzzle velocity instead of the older 870-890m/s velocity ammo. The M23 used a lighter projectile but it was filled with six times the amount of incendiary material as the M8 API round used in the last couple years of WW II.

Granted the 20mm guns and ammo had also improved but the six guns on the Sabre were worth nine WW II guns and were delivering almost 720 grams of incendiary material per second compared to the 106 grams of incendiary material per second delivered by eight .50 cal guns on a P-47.

They probably should have shifted to the 20mm like the Navy did but the .50 hadn't stood still.

 

[GregP]

Guns had nothing whatsoever to do with the size of the P-47. The size was dictated by the turbocharger installation.

The pilot sat between the two hot tubs and the cockpit was warm. In Europe, this was a bonus in winter and disadvantage in summer. The wings were large enough to handle 8 x 50-cal plus ammo. This aircraft is currently flying.

Today, they just taxied another one that was recovered from a lake. EVERYTHING works, including the turbo! Dottie Mae!


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