In message , Kevin
Brooks writes
"Paul J. Adam" wrote in message
...
Checking, that's true - on the other hand, you did a lot more damage
with the 20mm guns. I recall a vivid account from a Hurricane pilot
flying night intruder over France, describing his firing pass on a
German bomber in a Hurricane IIC; and his startled surprise at how the
aircraft caught fire and went out of control almost at once, compared to
the long 'squirt' needed with machine-gun fire.

Yeah, and the .303's in the Hurricane were not .50 cals, were they?

Nor were they 20mm.

I
believe one can also find plenty of examples of MG fire quickly
destroying both german and Japanese aircraft during WWII (i.e., all of
those large deflection snap shots).

And yet the USN felt a need to get 20mm into the Fleet, because it would
destroy Kamikazes more quickly and reliably.

I doubt it, or the RAF would have stuck with .303".

I do believe ammo volume was a concern for the USAAF; one has to
wonder if the 20mm was so invaluable, why did it get dumped from so
many aircraft? I belive a lot of P-38's dumped them, as did the B-29
in its tail armament (we went through this a while back--issue being
both weight *and* performance problems).

The B-29 often also dumped most of its turreted .50" guns other than the
tail pair - shall we assume that a shocking flaw was suddenly found with
the .50"?

The USN switched to 20mm guns for its new-production fighters and
dive-bombers (the dive-bombers arrived before the end of the war, the
fighters mostly didn't) but the USAF didn't.

Partly correct. The USN "sort of" switched, as best I can figure; they
produced MG armed fighters to the very end of the war, I believe (even
the vast majority of the -4 series of Corsairs were MG armed). The
20mm did not come into large scale USN/USMC fighter use until after
the war, and even then they retained MG armed aircraft like the
Corsair through the Korean conflict.

"Retained" because there wasn't much new production, rather than from
choice.

Burst effect is handy when strafing groups. It also ups lethality
against a lot of soft targets (using HEI) and harder targets like APCs
and self-propelled guns (using AP).

The 20mm of the day (not the same as todays more powerful charges,
both propellent and filler wise) was not the big hitter that you
apparently believe it was, IMO.

Not a "big hitter" but more powerful than .50".

Plenty of German vehicles, including
armored ones, were killed by the ol' .50 cal, too.

Plenty of German vehicles killed by .303" strafing, but that doesn't
make it a superior weapon. You keep waving this strawman that because
the 20mm was more lethal, I'm claiming that the 50" was somehow meant to
be ineffective, and that just isn't so.

Not in question. But would the P-47 have done better with four or six
20mm vice eight .50s? (or twelve .30s, for that matter?)

I doubt it would have really been any more effective with the cannon
armament.

Really? What's the basis for that analysis?

To take a different example, the US Army replaced the M-1 with the M-14.
Does that mean the M-1 was a flawed, ineffective weapon and a dangerous
liability to the troops carrying it? Don't think so, somehow.

Careful. By that approach, we went to the 5.56mm over the 7.62mm
because volume of fire became more important than hitting power--what
does that say about the .50 cal vs 20mm argument?

Given that a reason why the USAF abandoned the .50" was because it
visibly lacked lethality against the MiG-15 (many kills, but also many
recorded cases of 'lost kills' where MiGs were hit and still escaped) it
says quite a lot.

What's the relative numbers of A-36s and P-47s in USAAF service, and a
sortie count for each?

Hey, no argument that the P-47 was the better CAS/BAI platform--but
the P-51/A-36 was indeed used for ground attack during WWII, and in an
amount that IMO exceeds the "wasn't much used" that you have
attributed to it.

What's the relative sortie count?

What _is_ interesting is that the F-51 was forced into the role for
Korea, where the P-47 would definitely have been better suited to the
role.

Driven by the fact that they had F-51s available to reactivate rather
than a superiority for the mission.

Who cares what drove it--

I do.

it was used in that role.

And does that indicate that it was the best option possible for that
role? Or does it indicate that it was all that was available?

This is why the reasons are important.

It was by war's end, but certainly not by enough to justify a retrofit
program.

And what great advances in the 20mm "by wars end" made it a hands-down
better weapon?

Comparable rate of fire, considerably more destructive projectile.

Why was the F-86 so succesful when armed with MG's?

How many kills did it lose because the MGs weren't able to reliably kill
MiGs? Flicking through Jackson's "Air War over Korea" reveals as many
MiGs 'damaged' as confirmed killed by Sabres, because while the F-86
could get into firing position, and the .50" battery was accurate and
would get hits, it took an average of a thousand rounds of .50" to down
a MiG (which meant a Sabre carried only two stored kills on that
average).

Compared to how much in .50 ball?

When you consider the velocity and mass of the what, five or so .50
cal rounds that are hitting the target for every one old straight neck
20mm round?

Nope. Typical installation would be six .50" guns firing at ~750rpm, so
a one-second burst looses off 75 rounds of .50 ball. Compare that to
four Hispano V, also firing 750rpm - you're looking at sixty rounds of
mixed HE and AP, or seventy-five rounds of ball.

(The faster-firing M3 .50" was a post-war innovation, confined to the
USAF - that would get you 120 rounds in a one-second burst from six
guns, but they're still only ball rounds)

You keep leaping to the assumption that "an alternative might have been
better" means that "the existing weapon wasn't adequately lethal".

No, I am "leaping to the conclusion" that you cannot support your
earlier assertion that the 20mm was a hands-down better weapon for
strafing.

So, why is the A-10 armed with a 30mm cannon instead of a battery of
..50" guns? For that matter, why were the A-1, A-4, and A-7 all
cannon-armed rather than using machine-guns?

Persoanally, I see advantages for both weapons, and figure
that they probably were around equally effective in the strafing role.
The effectiveness of the P-47 and MG-armed Corsair, the F6F, etc.,
prove that the .50 cal was a very effective weapon for strafe
missions;

It proves nothing about how those missions might have gone, had they
been armed with something different.

I have seen nothing that shows definitively that the
heavier, lower velocity, lower rate of fire, and more jam-prone 20mm
weapons of the day were demonstrably superior to them.

Rate of fire? Nope, the Hispano V fired just as fast as the M2 Browning
(750rpm each)

Reliability? Many aircraft had problems with their gun installation
(including the P-51), typically with jamming caused by wing flex
distorting gun mounts or ammo feeds. Not a gun issue, a mounting issue.

Low muzzle velocity? 880m/s for a .50, 850m/s for a Hispano V (which had
a shortened barrel - 880m/s was typical for longer 20mm).

Heavier? 29kg for the .50" gun, 42kg for the Hispano - so six M2s end up
heavier than four Hispanos.


I can point to the US Navy's decision sometime in 1943 or 1944 to
require new aircraft to be armed with cannon rather than guns, and to
the extinction of the .50 post-Korea (replaced, in aircraft like the
F-100 by... guess what, four 20mm cannon!)

Gee, are you gonna tell all those F6F pilots around during August 45
that their aircraft were underarmed?

By war's end, yes. "Underarmed" is a relative term, of course: they had
an effective battery, but it was possible to do better.

What about the MG armed Corsairs
of Korea?

Likewise. The Corsairs weren't the aircraft of choice for Korea, they
were used because they were available.

And that those MG armed F-86's racked up a much higher kill
ratio against those (I guess) superior armed Mig-15's?

And yet the Sabre's MGs proved lacking in lethality... allowing many
MiGs to limp away, and driving a shift to heavier calibres.

As another
poster has pointed out, the USAF went to the 20mm in-mass when the
later M39 became available--early efforts with the 20mm in that poor,
underarmed F-86F were unsuccessful.

Due to gun gas ingestion, rather than any flaws in the weapon. (Similar
problems plagued the RAF's Hunter and Swift development - the 30mm ADEN
worked just fine, it was persuading the engine not to guzzle the muzzle
blast and stall that was a problem)

To be really sarcastic, why is the A-10 built around a 30mm Gatling when
(by this tally) a noseful of .50s should be so lethal and effective?

Paul, you are truly stretching here.

No, I'm asking why a unique, heavy and expensive weapon was chosen for
ground-attack in favour of a cheaper, lighter alternative.

What does this have to do with
your complete inability to provide definitive proof that the .50 cal
was deficient in comparison to the 20mm's of the day in the ground
attack role?

I'm giving you the data, you're ignoring it and insisting that I'm
"claiming it was deficient". It was at least adequate: it's just that
there were alternatives that were even better.

Can you show us where the Typhoon was so radically more
lethal than the P-47?

Neither used their guns as their primary air-to-ground armament, and
there was no radical difference in lethality between US and UK bombs and
rockets.

Was that a deliberate choice, or the USN using what it had?

Who cares?

It's significant because it drives the results.

The fact is that the .50 cal was still being used in great
numbers by the USN years after you indicated the USN gave up on it
because it was not up to their needs.

The USN didn't "give up on it", they elected to procure new aircraft
armed with 20mm rather than .50. That decision was affected by the end
of the war, the procurement slowdown, and the Korean malaise that
strength couldn't be diverted from Europe and so Korea was fought with
reserve stocks (the saga of F-84 deployment is a good example)

Yes, they did, for all new designs and production. The results of that
decision mostly just missed the war.

The decision to change armament leads aircraft in combat by eighteen
months to two years. Which new USN fighter design from 1944 or 1945 used
machineguns rather than cannon?

Not during WWII it did not.

Look at the F8F Bearcat: first flight in 1944, just missed combat
service in 1945. About eighteen months.

Or the
B-17E/F/G gestation period.

How about the B-29 gestation? Or the F-80? By war's end, it was taking
longer to get aircraft from concept to service.

The F4U night fighter variant did, IIRC, use the .50 MG's.

Was it new-build or a conversion?

And all of
the serving fighters which continued into production throught the end
of the war continued to retain the .50 cal, with the exception of some
400 copies of the -4 Corsair series.

"Retained" is not the same as "new designs armed with", of course.

Not surprising - the Hunter and Swift both had major problems with gun
firings choking the engine.

http://home.att.net/~jbaugher1/p86_25.html

is interesting - sounds like they got the problems fixed pretty well.
They then put the de-bugged 20mm gun package into the F-86H, for ground
attack use... suggesting that it was considered more effective in that
role.

More than just debugged, I believe--they deleted part of the original
load, and I am not sure that the 20mm guns in the H were even the same
model as those tried out in the E/F trial. And yes, they were starting
to look at improving the hitting power--the newer cannon being more
reliable than the older 20mm's, and with the threat changing as
well--none of which has anything to do with the fact that the .50 cal
in the CAS/BAI role during WWII was not demonstrably less effective
than the 20mm.

Basic OA indicates that it most definitely was. Same problems applied to
the AC-130's armament evolution, which started out with 4 x 7.62mm and 4
x 20mm guns, and rapidly jettisionned the 7.62mm and some 20s to add
40mm guns. Provided you could get hits, explosive shell was a lot more
lethal than ball.

About 5% of production, compared to 15% of Corsairs built with cannon?
Do I hear moving goalposts?

No. You hear a statement of fact--the latter US production run did
bring the 20mm into service, contrary to your claim that "mostly if
not all" cannon armed Sabres were foreign.

I'd call 95% "most" - what would your definition be, considering that
elsewhere 15% is "a small minority"?

The MG armed Sabres were
rplaced in active service by the F-100 and F-86H, with both later
replacing the earlier F-86's in the ANG in good time (not sure what
the history of the ANG F-86 early models was--did they have the .50
cals removed and replaced by 20mm?).

At that point, I'd guess the aircraft were left as-is until replaced.

--
When you have to kill a man, it costs nothing to be polite.
W S Churchill

Paul J. Adam MainBoxatjrwlynch[dot]demon{dot}co(.)uk