How would you have armed the P38 if you were to use it as it was used historically?
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Lighthunmust
Banned
I think 6 .50s in the nose may not have been possible or if possible not provide enough room for adequate ammunition. Having projectiles with the same trajectory is very desirable. However all types of .50cal ammunition do not have the same trajectory, just closer than differing calibers unless the other caliber is specifically matched to it. There is a .50cal spotting cartridge that is matched to the M40 106mm recoiless rifle for example.
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Shortround6
Major General
The trajectory difference and time of flight difference wasn't enough different to worry about at any practical range.
Sight in trajectory chart:
View: https://www.youtube.com/watch?v=-p8h43TRXwk
Sight in trajectory chart:
View: https://www.youtube.com/watch?v=-p8h43TRXwk
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Lighthunmust
Banned
Shortround6 you're awesome! I should have mentioned that trajectories were "close enough for government work" but your chart proves "a picture is worth a thousand words".
Shortround6
Major General
All I know is what's what on the video. There may be longer clips out there. Since everything on site had to be flown in or brought in by sled(?) I would guess there wasn't much of value in the drum (fuel/oil).
fastmongrel
1st Sergeant
If we can have any gun from WWII how about 4 x Beresin B20 cannon. Roughly the same size as a Browning .50 so 4 of them should fit no problem.
davebender
1st Lieutenant
P-38 Mission Requirements.
Lockheed P-38 Lightning - Wikipedia, the free encyclopedia
Unfortunately the U.S. Army Air Corps did not have a reliable aircraft cannon. Otherwise I would recommend 4 x 20mm cannon mounted in the nose or along the fuselage sides.
Lockheed P-38 Lightning - Wikipedia, the free encyclopedia
Other then the occasional enemy recon aircraft the interception of hostile aircraft at high altitude means attacking heavy bombers.
Unfortunately the U.S. Army Air Corps did not have a reliable aircraft cannon. Otherwise I would recommend 4 x 20mm cannon mounted in the nose or along the fuselage sides.
Shortround6
Major General
In 1937 just what constituted a heavy bomber? even going by what was on the drawing boards what was a heavy bomber of 1940-41 going to look like?
The 20mm Hispano gun may have been the 3rd choice for a cannon. Early proposals may have used a 23mm gun or even a 37mm. The 23mm didn't pan out and the 37mm that made it into service used a feed system that wouldn't fit. The Hispano in the P-38 seems to have given less trouble than in other American installations, perhaps because of the rigid (but heavy) mounting cradle used in the P-38.
Once the Mission changes to long range flights heavy batteries of 20mm guns may not be a good idea. The Hispano had up to 15 seconds of firing time. even using 300rpg of .50cal ammo gives 21 seconds while 500rpg gives about 35 seconds of firing time.
It also worked out that no opposing countries actually built heavy bombers in any great numbers. If they had we might have seen alternative armaments. They did plan two 20mm and four .50s for the XP-49.
davebender
1st Lieutenant
Boeing B-17 Flying Fortress - Wikipedia, the free encyclopedia
The P-38 was an American fighter aircraft. So I've got to assume the U.S. Army Air Corps had enemy aircraft similiar to the B-17 in mind when they wrote specifications for a high altitude interceptor. Even if nobody else had a B-17 size bomber it was only a matter of time before they did.
Shortround6
Major General
By Jan 31 1939 the B-17 design had progressed to the delivery of the Y1B-17A, the 14th airframe in the B-17 series and the first to be equipped with turbo chargers. No armor or self sealing fuel tanks and defense was by FIVE hand aimed .30 cal machine guns in single mounts. Engines had 1000hp for take-off and 800hp at 25,000ft. The first real production model is the "B" with more powerful engines, still no armor or self sealing tanks and still with FIVE .30 cal guns. .50s don't show up (FOUR hand aimed single guns) until the "C" model which was ordered in 1939 and not delivered until the summer of 1940.
In 1937 just which B-17 equivalent should they have been planning to shoot down?
The B-17E, which started the series that made the B-17s real reputation wasn't ordered until the summer of 1940.
In 1937 just which B-17 equivalent should they have been planning to shoot down?
The B-17E, which started the series that made the B-17s real reputation wasn't ordered until the summer of 1940.
renrich
Chief Master Sergeant
The P38 had about 15 seconds of firing time with the 20mm and around 33 seconds with the .50s. I expect that the 20mm could be turned off so that only the .50s fired. I think the mix of weapons was good because if the 20mm ran out of ammo there was still a lot of lethality left in the .50s. Unless the .50s were sighted to give a box pattern, those four gun's concenrtrated fire was deadly.
davebender
1st Lieutenant
How reliable was the P-38s 20mm cannon during historical combat operations?
Jabberwocky
Staff Sergeant
On the P-38 in VIII AF service, the AN-M2 had one stoppage about 1 per 505 rounds in 1944, between Jan-1944 and Jul-1944. Reliability improved markedly about Apr/May-1944, as the P-38 transitioned away from the long-range escort mission to fighter bomber and ground strafing missions.
This overstates the reliability of the weapon in US service though. In 1942 and 1943, the average reliability was about 1 stoppage per 160-180 rounds, improving to about 1 per 200 in early 1944.
In comparison, the .50 had 1 stoppage per 3,900 rounds on the P-38 between Jan-1944 and Jul-1944. In VII AF service in the same period, average reliability was 1 stoppage per 1447 rounds (1 per 951 for P-51B/C, 1 per 1441 for P-51D, 1 per 1800 for P-47D).
This overstates the reliability of the weapon in US service though. In 1942 and 1943, the average reliability was about 1 stoppage per 160-180 rounds, improving to about 1 per 200 in early 1944.
In comparison, the .50 had 1 stoppage per 3,900 rounds on the P-38 between Jan-1944 and Jul-1944. In VII AF service in the same period, average reliability was 1 stoppage per 1447 rounds (1 per 951 for P-51B/C, 1 per 1441 for P-51D, 1 per 1800 for P-47D).
Jabberwocky
Staff Sergeant
If it was me I'd arm the P-38 with four B-20s. The gun is an upscaled UB, which fired the potent 12.7 x 108 ammunition.
Its slightly smaller and lighter than the M2 Browning (25 kg vs 29 kg), but the round is slower (750-790 m/s vs 850-880 m/sec) and the RoF is a little lower (800 rnds/sec vs 750-850 rnds/sec).
Against this, the round weighs 2.2 times as much and carries 5-6 times the incendiary material or 6.5 times the amount of HE. The actual ammunition (brass, propellant, round et al) is just 60% heavier than a .50 shell.
Pound-for-pound, a B-20 has about 2.5 times the potential lethality of a M2 Browning.
Take out the 4 Brownings and the Hispano (total weight of guns an ammunition is a staggering 960lbs/436.5 kg). Replace them with 4 B-20s with 260 rpg (20 seconds firing time) and the whole package comes out to 630 lbs/286.5 kg and a lethality increase of about 30%.
Its slightly smaller and lighter than the M2 Browning (25 kg vs 29 kg), but the round is slower (750-790 m/s vs 850-880 m/sec) and the RoF is a little lower (800 rnds/sec vs 750-850 rnds/sec).
Against this, the round weighs 2.2 times as much and carries 5-6 times the incendiary material or 6.5 times the amount of HE. The actual ammunition (brass, propellant, round et al) is just 60% heavier than a .50 shell.
Pound-for-pound, a B-20 has about 2.5 times the potential lethality of a M2 Browning.
Take out the 4 Brownings and the Hispano (total weight of guns an ammunition is a staggering 960lbs/436.5 kg). Replace them with 4 B-20s with 260 rpg (20 seconds firing time) and the whole package comes out to 630 lbs/286.5 kg and a lethality increase of about 30%.
wwii:)aircraft
Airman
- 32
- Jul 20, 2009
6 .50 cals. Americans weren't really known for their 20mm cannons. 6.50cals in the nose would be devastating. The only way I would choose the 20mm cannon over the M2 .50cal is if the cannon was a Germany Mg 151/20 which has a very high rate of fire.
Shortround6
Major General
Thank you for the numbers, I had read that the reliability in the P-38 was better than in other planes but I didn't know how much. BTW I believe Tony Williams says that the 'total' armament package for the P-38 weighed 1440lbs IIRC. guns, ammo, mounts, ammo boxes/chutes chargers, heaters, etc.
Aircraft structure has to be able to withstand the recoil loads. Clever mounts can help absorb the recoil or spread out the impulse over time reducing the peak loads but such mounts will add at least a bit more weight.
Jabberwocky
Staff Sergeant
American's aren't known for their 20 mm cannon because they mucked up copying the design from the French (and then the British). Took them most of the war to sort it out. Plus, US 20mm ammunition was initially susceptible to misfires if there was a lightly struck cap.
MG 151/20 RoF was good, but not great when it comes to WW2 20 mm cannon:
HS.7 / HS.9: 6.5 rps
Ho-1 / Ho-2: 7 rps
20mm Type 99-1: 8 rps
20mm Type 99-2: 8 rps
MG-FF: 8 rps
Hispano II: 10 rps
HS. 404: 11.5-12.5 rps
MG 151/20: 12 rps
Hispano V: 12.5 rps
Berezin B-20: 13 rps
ShVAK: 13 rps
Ho-5: 14 rps
