WWII 20mm cannon in planes

[zxcv]

It seems to me that the Germans and Japanese had a lot more cannon in their
planes than the Americans who seemed to rely almost totally on .50 machine
guns.

Why was that? What was the rate of fire or the 20mm cannons and what type
of projectiles did they fire?

[steve gallacci]

zxcv wrote:
>
> It seems to me that the Germans and Japanese had a lot more cannon in their
> planes than the Americans who seemed to rely almost totally on .50 machine
> guns.
>
> Why was that? What was the rate of fire or the 20mm cannons and what type
> of projectiles did they fire?

The US .50 BMG was a pretty good gun, reasonable rate of fire, hard
hitting round, and good velocity/range. The German 13mm gun was rather
weak by comparison and 20mm (and later, 30mm and larger) explosive or
incendiary shells were considered good bomber killers, though had
somewhat poorer velocity/range. For most applications, .50 fire was more
than adequate for most combat, especially as you could put more guns and
ammo in the plane compared to 20mm. It wasn't until things like the
toughness of MiG15s in the Korean War and the need for good bomber
killer rounds for US fighters that the limits of the .50 became more of
an issue.
On the other hand, the Brits (and the US Navy?) used 20mm during the war.

[Kevin Brooks]

"steve gallacci" > wrote in message
...
>
>
> zxcv wrote:
> >
> > It seems to me that the Germans and Japanese had a lot more cannon in
their
> > planes than the Americans who seemed to rely almost totally on .50
machine
> > guns.
> >
> > Why was that? What was the rate of fire or the 20mm cannons and what
type
> > of projectiles did they fire?
>
> The US .50 BMG was a pretty good gun, reasonable rate of fire, hard
> hitting round, and good velocity/range. The German 13mm gun was rather
> weak by comparison and 20mm (and later, 30mm and larger) explosive or
> incendiary shells were considered good bomber killers, though had
> somewhat poorer velocity/range. For most applications, .50 fire was more
> than adequate for most combat, especially as you could put more guns and
> ammo in the plane compared to 20mm. It wasn't until things like the
> toughness of MiG15s in the Korean War and the need for good bomber
> killer rounds for US fighters that the limits of the .50 became more of
> an issue.
> On the other hand, the Brits (and the US Navy?) used 20mm during the war.

The USN started to switch to the 20mm during the latter part of the war, but
it also produced .50 cal armed aircraft through the end of the war, too. If
the original poster will do a search using google news, he will find that
this topic has repeatedly been beat to death in this NG, and likely find
some items of interest to him.

Brooks

[Keith Willshaw]

"zxcv" > wrote in message
...
> It seems to me that the Germans and Japanese had a lot more cannon in
their
> planes than the Americans who seemed to rely almost totally on .50 machine
> guns.
>
> Why was that? What was the rate of fire or the 20mm cannons and what type
> of projectiles did they fire?
>
>

Because most continental powers were using .30 calibre MG's and often
only mounted 2 or 4 of them which gave pretty poor firepower

4 or 6 .50's give a much better armament and less incentive to
move to cannon. Various calibre cannon were tried with some success
and towards the end of WW2 the USN started to adopt it more
rapidly.

Keith

[Cub Driver]

The American fifty-caliber machinegun was a formidable weapon,
especially against fighters. This size bullet was rarely used by other
nations, who tended to favor rifle-caliber (.30-cal or 7.x mm)
machineguns. The A6M2 Zero had two rifle-caliber guns and two 20 mm
cannon. The Wildcat with four fifties came out even against the Zero
during the first year of the war, despite the fact that the U.S.
pilots started out with the disadvantage of no combat experience. And
the Wildcat wasn't even considered a first-class American fighter!

When Germany and Japan realized they had to up-gun their fighters in
order to prevail against heavily defended and armored American
bombers, they naturally favored cannon. After the first year of the
war, the U.S. didn't have to contend much with enemy bombers; the
Americans were on the offensive, and U.S. fighters mostly battled
enemy fighters.

>It seems to me that the Germans and Japanese had a lot more cannon in their
>planes than the Americans who seemed to rely almost totally on .50 machine
>guns.
>
>Why was that? What was the rate of fire or the 20mm cannons and what type
>of projectiles did they fire?
>

all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com

[pendell]

"zxcv" > wrote in message >...
> It seems to me that the Germans and Japanese had a lot more cannon in their
> planes than the Americans who seemed to rely almost totally on .50 machine
> guns.
>
> Why was that? What was the rate of fire or the 20mm cannons and what type
> of projectiles did they fire?

Question for the group at large ...

.... did it have anything to do with the fact that the Germans were
gunning for B-17s and such, and therefore needed a weapon that had a
low rate of fire and less accuracy but a heavy punch? Whereas the
Americans, whose fighters mostly did escort over europe, needed a
weapon with better accuracy and a higher rof?

Just curious.

Respectfully,

Brian P.

[Tony Williams]

"zxcv" > wrote in message >...
> It seems to me that the Germans and Japanese had a lot more cannon in their
> planes than the Americans who seemed to rely almost totally on .50 machine
> guns.
>
> Why was that? What was the rate of fire or the 20mm cannons and what type
> of projectiles did they fire?

See: http://www.quarry.nildram.co.uk/WW2guneffect.htm for full details
of WW2 fighter guns and ammunition, and a comparison of their
effectiveness.

As other responders have said, the .50 was a good gun which met USAAF
needs (although the USN would have preferred to make more use of the
20mm). Other nations preferred to use cannon as they were more
destructive, even when (like the USSR) they had a good HMG available.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[ArtKramr]

>Subject: Re: WWII 20mm cannon in planes
>From: (Tony Williams)
>Date: 3/8/04 9:52 PM Pacific Standard Time
>Message-id: >
>
>"zxcv" > wrote in message
>...
>> It seems to me that the Germans and Japanese had a lot more cannon in their
>> planes than the Americans who seemed to rely almost totally on .50 machine
>> guns.
>>
>> Why was that? What was the rate of fire or the 20mm cannons and what type
>> of projectiles did they fire?
>
>See: http://www.quarry.nildram.co.uk/WW2guneffect.htm for full details
>of WW2 fighter guns and ammunition, and a comparison of their
>effectiveness.
>
>As other responders have said, the .50 was a good gun which met USAAF
>needs (although the USN would have preferred to make more use of the
>20mm). Other nations preferred to use cannon as they were more
>destructive, even when (like the USSR) they had a good HMG available.
>
>Tony Williams
>Military gun and ammunition website: http://www.quarry.nildram.co.uk
>Discussion forum at: http://forums.delphiforums.com/autogun/messages/
>


Seems lik there was a lot of indecision about our use of canons, When we were
told that our Marauders were being replaced by Invaders they also announced
that the Invaders would come with a 75mm cannon mounted in the nose. We got
the Invaders OK but nary a cannon in sight, We didn't have much to complain
about since it had 14 50's firing forward. But I alway s looked forward to
using that 75mm cannon and was sorry when they didn't arrive, I think one
reason was it had to be hand fed by a guy in the right seat which would have
given it a very slow rate of fire.When we flew warhead A-26's I was the guy in
the right seat. I only flew in the nose on Norden equipped models.II sure
would have loved to have had the 75mm cannon to play with. (sigh)


Arthur Kramer
344th BG 494th BS
England, France, Belgium, Holland, Germany
Visit my WW II B-26 website at:
http://www.coastcomp.com/artkramer

[Tony Williams]

(pendell) wrote in message >...
>
> Question for the group at large ...
>
> ... did it have anything to do with the fact that the Germans were
> gunning for B-17s and such, and therefore needed a weapon that had a
> low rate of fire and less accuracy but a heavy punch? Whereas the
> Americans, whose fighters mostly did escort over europe, needed a
> weapon with better accuracy and a higher rof?

Not really. The Luftwaffe adopted the 20mm version of the MG 151
(rather than the original high-velocity 15mm version) long before they
had the USAAF to worry about. To deal with the B-17, they found 20mm
wasn't adequate and went up to 30mm. The Russians also went for 20mm
guns rather than 12.7mm as the war progressed, and they never had
heavy bombers to worry about.

A good 20mm cannon simply had a better power-to-weight ratio than a
..50 cal HMG because it was the smallest calibre to carry a useful HE
charge. So you got more destructiveness for a given armament weight.

The USAAF stuck with the .50 simply because that's pretty well all
they had; fortunately, it proved good enough.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

[zxcv]

"Emmanuel Gustin" > wrote in message
...
> "pendell" > wrote in message
> om...
>
> > ... did it have anything to do with the fact that the Germans were
> > gunning for B-17s and such, and therefore needed a weapon that had a
> > low rate of fire and less accuracy but a heavy punch?
>
> Like most WWII weapons, the 20 mm cannon were developed
> during peacetime, a considerable time before the first B-17s
> appeared over Europe. Combat experience did not play a large
> role in to the decision. (There was of course some experience in
> Spain and China.) It was more a matter of, as engineering usually
> is, balancing different factors to find the optimum. The big factors
> were destructiveness, hit probability (rate of fire and muzzle
> velocity) and weight. The first favours bigger guns, the second
> usually favours smaller-calibre weapons, and the third generally
> favours bigger guns again (although they are heavier, they give
> more hitting power for the same installation weight; for example,
> a single .50 is equivalent to about four .30 Brownings.)
>
> The wide consensus during WWII was that the optimum was
> around 20mm. Given the same technology, rate of fire and muzzle
> velocity were not much lower; the gun was heavier but the
> ammunition far more effective. Later several heavy machine guns
> were modified to 20 mm cannon (the Soviet ShVAK and B-20, the
> German MG 151/20, and the Japanese Ho-5) because they were
> judged to be more effective in that form. The USAAF did not follow,
> in part because of a different doctrine, and in part because its gun
> development budgets between the wars were largely hypothetical
> in nature.
>
> > Whereas the Americans, whose fighters mostly did escort over
> > europe, needed a weapon with better accuracy and a higher rof?
>
> It was less a matter of what they needed than what they had. But
> the big advantage of the .50 was that a large stock of ammunition
> could be carried. A good 20mm cannon would have offered similar
> rates of fire and accuracy (although with the limitation that only
> four would have been installed instead of six) and more firepower,
> but the total available firing time would have been much shorter.
> For an escort fighter that was a very important consideration. For
> this reason, for example, the USAF decided against a plan to install
> four 20mm cannon in the nose of the P-38: The .50s had 500 rounds
> (40 seconds of fire) but the cannon only 150 (15 seconds).
>
> --
> Emmanuel Gustin
> Emmanuel.Gustin -rem@ve- skynet dot be
> Flying Guns Page: http://users.skynet.be/Emmanuel.Gustin/
>
>
>
>

What about planes with multiple fixed guns that had different amounts of
ammunition/fire time -- did the pilot have a selector to determine which
guns would fire or did everything fire when the trigger was pulled and some
guns would run out first?

[Regnirps]

"zxcv"

>It seems to me that the Germans and Japanese had a lot more cannon in their
>planes than the Americans who seemed to rely almost totally on .50 machine
>guns.

>Why was that? What was the rate of fire or the 20mm cannons and what type
>of projectiles did they fire?

I think it is pretty simple. They needed to shoot down bombers. We needed to
kill fighters. Eight Brownings with a nice synchonization gave a good spread
out to 300 yards or so. The folks with the cannons could fire from further away
at bigger targets and try to keep out of the massive MG fire of the bomber
formations.

I have some pictures of P47's with 20mm battle damage -- most hit from the
rear.

-- Charlie Springer

[Tony Williams]

"zxcv" > wrote in message >...
>
> What about planes with multiple fixed guns that had different amounts of
> ammunition/fire time -- did the pilot have a selector to determine which
> guns would fire or did everything fire when the trigger was pulled and some
> guns would run out first?

Generally speaking, where the planes were equipped with homogenous
armament (e.g. eight .303s or six .50s) they all fired together,
without the option. Where a plane had mixed armament (e.g. cannon and
MGs) it was possible to fire them separately or together.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/

[Dave Eadsforth]

In article >, zxcv
> writes
>"Emmanuel Gustin" > wrote in message
...
>> "pendell" > wrote in message
>> om...
>>
>>
>>
SNIP of Emmanuel's usual good stuff

>
>What about planes with multiple fixed guns that had different amounts of
>ammunition/fire time -- did the pilot have a selector to determine which
>guns would fire or did everything fire when the trigger was pulled and some
>guns would run out first?
>
>
In RAF aircraft, nearly all fighters had either two gun buttons (e.g.
Mosquito FB for its 4 Brownings and 4 20mm cannon) or, (as in the case
of the Spit MkV - 4 Brownings and 2 20mm cannon) a button that 'rocked'
- one set of guns when the top was pressed, another set of guns when the
bottom was pressed, and all guns when the middle was pressed. To my
knowledge, only the Beaufighter MkI fired a mixture of guns with just
one button.

Cheers,

Dave

--
Dave Eadsforth

[Cub Driver]

>What about planes with multiple fixed guns that had different amounts of
>ammunition/fire time -- did the pilot have a selector to determine which
>guns would fire or did everything fire when the trigger was pulled and some
>guns would run out first?

Yes, certainly. You had selector switches.

Because of their limited number of cannon rounds, Japanese Zero pilots
used their rifle-caliber mgs as sighting weapons.

all the best -- Dan Ford
email: (requires authentication)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com