20mm cannon, best, worst, specs, comparison to LMG, HMG etc.

[Peebs]

In relation to the air defence over Northern Australia...

RAF tests showed that the Hispano cannons averaged 1 stoppage per 1500 rounds fired under normal opperating conditions.
This stoppage rate doubled in dusty conditions, ie the conditions of Northern Australia.

The Hispano cannon was also prone to freezing at low tempretures, ie above 25000 feet where most aerial combat to place over Australia.

A gun heating system that took hot air from the exhaust manifolds out to the wings was installed in an atempt to overcome this problem, however,
unacountably many spitfires were dispatched to Australia without this ducting.

moreover, many stoppages occured outside the gun itself, it has been reported that the Austin Belt Feed Mechanism was a failure as a weapon sysytem because of
the ammunitions belts propensity to jam.

So dispite claims that the Hispano's unreliability problems had been solved, the pilots defending Northern Australia fought their war with a cannon unable to cope
with the cold of altitude, the ingestion of dust from bush airfields and a unreliable ammuntion feed mechanism.

A pilots table of 15 march 1943 records that of 19 pilots to engage the enemy, 8 reported 1 or both cannons to have failed.

So, whereas the RAAF and RAF pilots defending darwin had a near 50% chance of having cannon malfunction, the Japanese pilots in thier Zero's fitted with
Oerlikon FF cannon, altough technically inferior in ballistics and hitting power, could be at least assured of the guns firing until the ammuntion supply was exhausted.


from 'Darwin Spitfires. The real battle for Australia' Anthony Cooper 2011

 

[pinsog]

140/150rpg.


Not much more, even the MK 21 with the new wing and 4 guns only carried 175rpg for inboard and 150 rpg for outboard guns. Of course a MK 21 weighed less with with full tanks and ammo boxes than a F6F-3 did with empty fuel tanks and ammo boxes.


No but that proves what? That 1100lbs of armament is better than 500-750lbs of armament?

The top score in a single day in Europe was by George Preddy, 6 fighters in one day, perhaps conditions in Europe were a bit different than in the Pacific?

If the aircraft can carry it, outperform enemy fighters, and shoot down more enemy fighters per mission than they lose, then I would vote "yes".

There were several "aces in a day" over europe to, they weren't limited to the pacific.

 

[Shortround6]

If the aircraft can carry it, outperform enemy fighters, and shoot down more enemy fighters per mission than they lose, then I would vote "yes".

I would vote 'yes' too but it doesn't tell you that .50 cal guns were better than 20mm guns. It only tells you that if you increase the weight of armament carried by 50% and are able to keep competitive performance you can shoot down more planes. It doesn't take a rocket scientist to figure that one out.

 

[Ratsel]

do not want to argue here, just curious, but its generally accepted that it takes anywhere from 15-25 MG151 hits to knock down a B-17. much less for the Mk108. so how many rounds would be needed for a 50cal to knock down a B-17? I know its a tough one to answer.. so just a best guess. thanks.

edit:

or a little guy, like an IL-2

 

[pinsog]

I would vote 'yes' too but it doesn't tell you that .50 cal guns were better than 20mm guns. It only tells you that if you increase the weight of armament carried by 50% and are able to keep competitive performance you can shoot down more planes. It doesn't take a rocket scientist to figure that one out.

Not necessarily BETTER, but BETTER FOR THE INTENDED TARGET. The 20mm were many times better for large 4 engined bombers, or even very tough, armored, well defended twin engined bombers such as A20, B25, B26, and A26's, but against a fragile little ME109 or a slightly tougher FW190, a 50 hit plenty hard and carried much more ammo with considerable longer firing time.

If you were German, there was no other choice but to carry cannon. The only thing I would argue for Germany was, they needed bigger, more powerful, high altitude, single engine fighters(P47 would have been perfect) to carry all the cannon they needed to bring down heavy bombers.

 

[Shortround6]

do not want to argue here, just curious, but its generally accepted that it takes anywhere from 15-25 MG151 hits to knock down a B-17. much less for the Mk108. so how many rounds would be needed for a 50cal to knock down a B-17? I know its a tough one to answer.. so just a best guess. thanks.

Best guess?? 45 to 75 hits?

Some people figure the MG 151 was about equal to the Hispano so figure 3 rounds of .50 equal 1 round of 20mm. (some other 20mm were not equal)

 

[Ratsel]

theres a pic of a lancaster ( shoulda saved the pic) that got riddled with 13mm hits (100s and 100s). most of the hits were not grouped, and did very little damage. when compared to another lancaster that got hit with 13mm 20mm hits, it was night and day. ie: devestating. written off I believe.

 

[pinsog]

Best guess?? 45 to 75 hits?

Some people figure the MG 151 was about equal to the Hispano so figure 3 rounds of .50 equal 1 round of 20mm. (some other 20mm were not equal)

I'm figuring a 3 second burst as a realistic minimum. Say 6 50's, 80 rounds thrown out, 48 hits, thats 60%. What would 4 20mm in a late war Spitfire or Typhoon throw out in a 3 second burst? Then use 60% as a hit ratio. I'm winging it here. Both bursts would destroy a small single engine target, like an ME109. So, how many 3 second bursts do both airplanes carry? My point being that both airplanes will spend far more ammo missing than hitting, and 6 50's give you more ammo to miss with until you get on your target.

 

[pinsog]

theres a pic of a lancaster ( shoulda saved the pic) that got riddled with 13mm hits (100s and 100s). most of the hits were not grouped, and did very little damage. when compared to another lancaster that got hit with 13mm 20mm hits, it was night and day. ie: devestating. written off I believe.

Cannon is the only way to go when shooting at 4 engine bombers. No argument there from me.

 

[Shortround6]

Not necessarily BETTER, but BETTER FOR THE INTENDED TARGET. The 20mm were many times better for large 4 engined bombers, or even very tough, armored, well defended twin engined bombers such as A20, B25, B26, and A26's, but against a fragile little ME109 or a slightly tougher FW190, a 50 hit plenty hard and carried much more ammo with considerable longer firing time.

For an equal weight and fire power the .50 didn't carry that much more ammo or have than much longer a firing time. in fact try this one.
two 20mm Hispano guns = 294lbs + 150lbs ammo (240 rounds, 120rpg)= 444lbs and has a firing time of 12 seconds.
four .50cal guns = 288lbs + 156lbs ammo (520 rounds, 130rpg) = 444lbs and has firing time of 10 seconds.

The 20mm guns are firing 20 shells a second vs the .50 cals 52 bullets a second. The 20mms are throwing 2.6 kg of projectiles a second while the .50s are throwing 2.24kg a second. Depending on the year you can adjust the amount of explosive or incendiary material carried. But with a single 20mm shell carrying about 10 times what an M8 API .50 cal did the .50 is going to come out on the short end. Adjust the rate of fire of the .50s up to 14 rounds a second, you get to 2.4 kg a second but time of fire shortens up 0.7 seconds. On average you need three times the number of .50 cal hits to do the same damage as a 20mm hit. I am just not seeing the advantage of the .50cal.
Did it do the job during WW II? Yes.
was it the best choice? No, in theory.
In practice US ordnance screwed up the US built Hispanos so bad they never lived up to their potential in US service and it is quite possible that the British never installed ANY of the thousands of lend lease US built guns in a combat aircraft. This sub par performance helps explain the US preference for the .50cal. But it is a bit like comparing a rather average car to better model except the test model of the better car is a lemon.

 

[Shortround6]

I'm figuring a 3 second burst as a realistic minimum. Say 6 50's, 80 rounds thrown out, 48 hits, thats 60%. What would 4 20mm in a late war Spitfire or Typhoon throw out in a 3 second burst? Then use 60% as a hit ratio. I'm winging it here. Both bursts would destroy a small single engine target, like an ME109. So, how many 3 second bursts do both airplanes carry? My point being that both airplanes will spend far more ammo missing than hitting, and 6 50's give you more ammo to miss with until you get on your target.

Germans figured an average pilot could get 2-5% hits against a bomber. It is why they went to the 30mm cannon. A single engine fighter could not carry enough ammo to get enough hits on a B-17 to bring it down.

 

[Shortround6]

I'm figuring a 3 second burst as a realistic minimum. Say 6 50's, 80 rounds thrown out, 48 hits, thats 60%. What would 4 20mm in a late war Spitfire or Typhoon throw out in a 3 second burst? Then use 60% as a hit ratio. I'm winging it here. Both bursts would destroy a small single engine target, like an ME109. So, how many 3 second bursts do both airplanes carry? My point being that both airplanes will spend far more ammo missing than hitting, and 6 50's give you more ammo to miss with until you get on your target.

A typhoon would throw out 120 rounds in 3 seconds. even 17 percent hits would give you 20 shell hits and probably a dead bomber. Six .50s would throw 240 rounds in three seconds.

 

[pinsog]

A typhoon would throw out 120 rounds in 3 seconds. even 17 percent hits would give you 20 shell hits and probably a dead bomber. Six .50s would throw 240 rounds in three seconds.

I was actually figuring a 1 second burst. Completely blew the 4th grade arithmetic.

 

[claidemore]

Dick Audet of 411 Sq RCAF got 5 in one day with a Spit IX. Burt Houle of 417 Sq RCAF got 5 in one engagement, with a Mk VIII, was not officially credited for it, but later research proved his claim correct. Clive Caldwell got 5 Ju87s in one day in North Africa flying a Tomahawk IIb, 2 x .50 and 4 x .303.
Pierre Le Gloan, French Air Force, shot down 5 in a day with a D.520, 1 x 20mm cannon, 4 x 7.5 mgs.
Two BoB pilots achieved ace in a day, one from 610 Sq, one from 501 Sq using . 8 x .303.
Finnish pilot Hans Wind got 5 in a day on five seperate occasions, flying a 109G6.
German pilot Emil Lang claimed 18 in one day flying a FW190, not sure what variant, but probably 4 x 20mm cannon and two mgs. If the gun loadout was the determining factor in multiple kills per day, then the multi cannon armament on the FW190 is the obvious choice (#2 guy with 17 kills/claims in one day flew FW190 as well), however there are many other factors that come into play.
Target rich environment being the first one to come to mind.
There are not as many cannon armed Spitfire pilots who achieved the ace in a day status, mostly because they never got the opportunity. The most common gripe you hear from late war Spitfire pilots is the lack of 'trade'. There were fewer and fewer opportunities for air to air combat for pilots in 2TAF because so many Luftwaffe resources were relegated to Reich defence. It had very little to do with the weapon loadout. I believe Wally McLeod RCAF downed a 109 with just 3 cannon shells? and Johnny Johnson was angry with himself for not matching McLeods performance when he used 17 rounds. (this is from memory, but it illustrates the point)

 

[Kryten]

the big advantage of the 20mm over the MG/HMG is in deflection shooting where its not possible to achieve multiple hits, a single hit from a 20mm can and did cause sufficient damage to either put the opponent out of the fight or damage the aircraft enough to cause controll problems leaving him in a seriously disadvantaged position!

 

[pinsog]

Dick Audet of 411 Sq RCAF got 5 in one day with a Spit IX. Burt Houle of 417 Sq RCAF got 5 in one engagement, with a Mk VIII, was not officially credited for it, but later research proved his claim correct. Clive Caldwell got 5 Ju87s in one day in North Africa flying a Tomahawk IIb, 2 x .50 and 4 x .303.
Pierre Le Gloan, French Air Force, shot down 5 in a day with a D.520, 1 x 20mm cannon, 4 x 7.5 mgs.
Two BoB pilots achieved ace in a day, one from 610 Sq, one from 501 Sq using . 8 x .303.
Finnish pilot Hans Wind got 5 in a day on five seperate occasions, flying a 109G6.
German pilot Emil Lang claimed 18 in one day flying a FW190, not sure what variant, but probably 4 x 20mm cannon and two mgs. If the gun loadout was the determining factor in multiple kills per day, then the multi cannon armament on the FW190 is the obvious choice (#2 guy with 17 kills/claims in one day flew FW190 as well), however there are many other factors that come into play.
Target rich environment being the first one to come to mind.
There are not as many cannon armed Spitfire pilots who achieved the ace in a day status, mostly because they never got the opportunity. The most common gripe you hear from late war Spitfire pilots is the lack of 'trade'. There were fewer and fewer opportunities for air to air combat for pilots in 2TAF because so many Luftwaffe resources were relegated to Reich defence. It had very little to do with the weapon loadout. I believe Wally McLeod RCAF downed a 109 with just 3 cannon shells? and Johnny Johnson was angry with himself for not matching McLeods performance when he used 17 rounds. (this is from memory, but it illustrates the point)

When you say, "shot down 5 in one day", you mean they shot down 5 in one flight correct?

When Emil Lang shot down 18 planes in one day, how many missions did it take for him to do that? My point on 50 caliber armamament for use against fighters only, is that 400 rounds per gun give enough ammo to shoot down 5 or more on a single flight without landing to reload.

 

[Ratsel]

there were many Luftwaffe pilots that got 5 in a day. actually 5 in 3 minutes, 5 in 4 minutes, 5 in 5 minutes, 5 in 10 minutes, 5 in etc.,etc.,etc. 20mm cannon hits played a huge part, along with pilot skill luck. Bartels ( I think ) got 4 P-38's in 40 seconds + a 5th 2 minutes later iirc.

 

[davparlr]

Just to remind everyone, the AAF was not hepped up on the 20 MM cannon as I posted earlier and it had little to do with the lethality of the 50 BMG versus the 20MM but rather the amount of bullets a fighter could put into the space the enemy occupied. As an aside, regarding the ground use of the 50BMG against E/A, if one looks at film of early WW2 the AA 50 BMGs had water jackets just like the Vickers and Browning 30 cals had.

There have been several statements about whether the different ballistic properties of the projectiles of the 50s versus the 20MMs caused problems. The AAF thought those different properties were a real problem and disliked mixed armaments on wing mounted guns. This from the Fighter Conference Report.

Also, according to the report, Navy Armament Rep, Commander Monroe, was enthusiastic, as armament people tend to be on different weapons (he also was enthusiastic about the 60 cal weapon (?)), on the 20 mm and thought the 20 mm would soon be prevalent in the Navy. He stated that the final decision would be left up to the fleet. It is interesting to note that this report was in October, 1944, almost one year later, August, VJ day, the great majority of Navy fighters including the latest F8F and future jets, FH-1, FJ-1 was still armed with the .50s. So, it is apparent that the Navy fleet had no problem keeping the .50s, for most likely good reasons.

 

[Shortround6]

Also, according to the report, Navy Armament Rep, Commander Monroe, was enthusiastic, as armament people tend to be on different weapons (he also was enthusiastic about the 60 cal weapon (?)), on the 20 mm and thought the 20 mm would soon be prevalent in the Navy. He stated that the final decision would be left up to the fleet. It is interesting to note that this report was in October, 1944, almost one year later, August, VJ day, the great majority of Navy fighters including the latest F8F and future jets, FH-1, FJ-1 was still armed with the .50s. So, it is apparent that the Navy fleet had no problem keeping the .50s, for most likely good reasons.

I can think of a lot of good reasons for the Navy "keeping" the .50s.

1. We have a lot of left over .50 cal ammo.
2. We have a lot of left over parts for .50 cal guns.
3. We would have to retrain our armorers.
4. We would have to print new (more) training manuals.

And probably more along those those lines.
The truth is the Navy "kept" the .50 cal for a very short space of time and only for planes whose design was well advanced.

There were 297 F4U-4Bs with 20mm guns and about 550 F4U-5s with 20mm guns completed post war along with about 200 close support models.

The 652 Bearcats with .50 guns were followed by another 600 with 20mm cannon.

While some F7Fs carried both the majority used four 20mm cannon.

The 60 FH-1 Phantoms (1600lb thrust engines) with .50 cal guns were followed by 762 FH-2 Banshee's (3000lb thrust engines to start) with 20mm cannon. Prototype contract was placed March of 1945, 5 months after the conference. the FH-1 can be traced back to Jan 1943, with final configuration decided on in early 1944.

The 30 NA FJ-1s were followed by the FJ-2s with 20mm guns but these were actually modified F-86Es so don't count.

Vought, however, did come up with the unlamented F6U-1 during this time frame (Navy request for proposals issued in Sept 1944) Plane had four 20mm cannon but might have been better with the .50 cal guns because of serious under power issues.

No Navy fighter after the ones mentions used .50 cal guns.

 

[pinsog]

I can think of a lot of good reasons for the Navy "keeping" the .50s.

1. We have a lot of left over .50 cal ammo.
2. We have a lot of left over parts for .50 cal guns.
3. We would have to retrain our armorers.
4. We would have to print new (more) training manuals.

And probably more along those those lines.
The truth is the Navy "kept" the .50 cal for a very short space of time and only for planes whose design was well advanced.

There were 297 F4U-4Bs with 20mm guns and about 550 F4U-5s with 20mm guns completed post war along with about 200 close support models.

The 652 Bearcats with .50 guns were followed by another 600 with 20mm cannon.

While some F7Fs carried both the majority used four 20mm cannon.

The 60 FH-1 Phantoms (1600lb thrust engines) with .50 cal guns were followed by 762 FH-2 Banshee's (3000lb thrust engines to start) with 20mm cannon. Prototype contract was placed March of 1945, 5 months after the conference. the FH-1 can be traced back to Jan 1943, with final configuration decided on in early 1944.

The 30 NA FJ-1s were followed by the FJ-2s with 20mm guns but these were actually modified F-86Es so don't count.

Vought, however, did come up with the unlamented F6U-1 during this time frame (Navy request for proposals issued in Sept 1944) Plane had four 20mm cannon but might have been better with the .50 cal guns because of serious under power issues.

No Navy fighter after the ones mentions used .50 cal guns.

20mm were definately the wave of the future as planes were getting tougher and tougher and the new aircraft had power to spare to carry what they needed to knock them down.