UK .303 / US.30 vs. Japanese aircraft

[Piper106]

Does anyone have any technical reports or other information on the effectiveness (or lack of effectiveness) of the British .303 and US .30 (7.62 mm) machine guns against the aircraft used by the Japanese during WWII??

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I have read several times that by the end of the Battle of Britian / fall of 1940 that the British felt that the .303 rifle caliber machine gun was not adequately effective against aircraft in the European theater. It took far too many .303 hits to knock out enemy aircraft, and larger harder hitting weapons were needed.

I wonder if against the more lightly built and less protected Japanese aircraft of the early Pacific war period if the British .303 and US .30 machines were still adequately effective.

Thanks for your help

Piper106

 

[Kocur]

Machine guns, i.e. weapons for 7-8 mm cartridges, had low effectiveness in Europe, because warplanes there got two things over time: armor for the crew and self sealing tanks. The former meant, that central unit could't be damaged form usual firing angles. The latter meant that probability of setting a plane on fire with mgs became negilgible.

Most of Japanese warplanes lacked both armor and selfsealing tanks. Any bullet hitting right place would do the damage. So it may be that eight .303s were better armament than any number of .50s. Mgs fired more bullets than hmgs and any of them had enough destructive power versus human body and plain fuel tanks.

 

[Clay_Allison]

Machine guns, i.e. weapons for 7-8 mm cartridges, had low effectiveness in Europe, because warplanes there got two things over time: armor for the crew and self sealing tanks. The former meant, that central unit could't be damaged form usual firing angles. The latter meant that probability of setting a plane on fire with mgs became negilgible.

Most of Japanese warplanes lacked both armor and selfsealing tanks. Any bullet hitting right place would do the damage. So it may be that eight .303s were better armament than any number of .50s. Mgs fired more bullets than hmgs and any of them had enough destructive power versus human body and plain fuel tanks.

I have often thought that as well and wondered if F4Fs and P-40s might have been well served to save weight by including .30 cals in place of .50s in the early phases.

 

[vanir]

I should suggest Tony William's website for detailed information on the subject.

Another thing to consider with light calibre guns might be effective range too. The fifties seemed to work very well for chopping up Japanese planes and remember the F4F was even upgunned in 1942 from 4 to 6 of them, facing Japanese aircraft. Spotter planes and the like used thirties, but these were considered defensive armament only.

 

[Tk3997]

Another thing to consider with light calibre guns might be effective range too.

That's was indeed a major factor the .50 had very nice ballistics and the large slug held it's velocity longer meaning when it did reach a target it delivered far more energy. This is the same reason we use it in sniper rifles and the like today. From what I've heard the 50 caliber was quite easy to aim having good range and a fairly flat trajectory. (A noticeable advantage over many early cannons which often lobbed shells more like a grenade launcher.)

30 caliber weapons would certainly would have been more effective then in Europe, but that is still relative. Also consider that early in the war the US fighters were fighting bombers and such as much as fighters and as the RAF learned in 1940 rifle caliber machine guns are totally inadequate for attacking twin engine bombers. Japanese planes might have been slightly more vulnerable, but there sheer size would likely allow them to soak a staggering number of smaller caliber hits all the same.

Another thing was that a .50 was big enough actually cause structural damage, you could chop a smaller plane up with a brace of .50s not merely poke holes in it. (Again why we often call it an anti-material round today) Then we get into the fact that even if the .30 might have killed a target early in the war US planes were inferior in many aspects of performance and often outnumbered too boot. Linger around pumping rounds into a Zero for half a minute while his friends swarmed around you hardly sounds like fun… The slightly lighter weight of the guns was not going to even vaguely close the performance gap and would piss away your only significant advantage which was firepower. Being able kill an enemy plane quickly and then move on certainly has value and the heavier guns also made snap shots (which was often all you got thanks to inferior performance) more effective as well.

US aircraft also often found themselves attacking ground or sea targets in this time period too. While .50 caliber was hardly going to sink a transport or light warship it was certainly better at tearing up equipment and suppressing AA guns. Japan had few armored vehicles of note, but I have little doubt the big bullet of a .50 was a much better bet for tearing up enemy troops and emplacements through jungle canopy then 7.62 was.

I think .50 caliber was the perfect weapon for the Pacific as it balanced damage, ballistics, payload and reliability under adverse conditions as well as allowing commonality between various aircraft types. It was also adequate if not outstanding in Europe which allowed still greater commonality and eased logistics.

 

[timshatz]

IIRC, the US Airforces in the Pacific, at least in some cases, went with standard ball .50 in place of AP as they found the ball would fragment inside japanese aircraft when hit whereas the AP would just sail right through.