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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.
All correct and all miss the point. There was no apparent ergency at the fleet to replace the .50s for the reasons you mentioned and mainly,....the .50s worked fine for the job they had to do, at least to the men whose life depended on them.
No, it does not miss the point. unless you are sending out refit kits to existing aircraft the replacement of .50 cal armed planes by 20mm armed planes didn't take that long, all things considered. It could take several months to get a plane from a factory door to an operational unit in the far pacific. Even refitting existing aircraft could have taken months from when the decision was made.
The US Navy bought 90 jets armed with .50 cal guns, the FH-1 design was started in 1943 and it was pretty much finalized months before the conference. The FH-2 Banshee with the 20mm cannon was being worked on in the Spring of 1945 with a full size mockup being completed in April 1945. It doesn't sound like the Navy was wasting much time in going for the 20mm cannon.
The work on the NA Fury was also well under way at the time of the conference. With prototypes ordered within weeks of the conference, preliminary design work would have going on for a number of weeks or months before hand, there is also the question of how much NA borrowed from the P-51 for this design for example it might have speeded things up to to copy as much of armament installation as possible (Fury 1 guns were in the wings).
As an example of how long it some times took things to get into service, the first F4U-4s came off the production line in Dec of 1944, but the first ones didn't reach the Philippines until April. at this point 500 had been produced. First operations of the F4U-4 aren't until May 1945. The Navy had ordered 300 F4U-4s with 20mm cannon back in Jan. of 1945. Now consider that the navy had issued a letter of intent to Vought to develop the F4U-4 model in Jan of 1944. 16-17 months from letter of intent to first combat use. While changing the guns isn't any were as big a project it wasn't going to be a matter of weeks to rearm the fleet.
I think that was a very good presentation of the arguments against the 20 mm., and it shows the Army's point of view, which I have been wondering about for a long time. We are going to let our case for the 20 rest entirely on the way the Fleet wants it. If the 20's are wanted, they will get them; if not, we will stick with the 50's. I think the 20's are coming in here shortly.
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.
Question: how many fighter sorties were flown by American pilots (airforce, navy and marines) during WWII?
My opinion is that, since they were not there shortly, the fleet must have felt that the 50's were adequate for job. If they had determined that they were inadequate or ineffective, I think the 20's would have already been in the pipeline. Apparently you disagree.
so what I'm getting from this thread is that:
2x MG131 + 1x MG151/20 is roughly = to 6x .50 or 8x .303.
so in comparison:
1x Mk108 would be roughly = to 2x MG131 + 1x MG151/20 or 6X .50 or 8x .303
1x Mk108 + 2x MG131 would be roughly =/> 8x .50
or am I off the mark here?
My opinion is that, since they were not there shortly, the fleet must have felt that the 50's were adequate for job. If they had determined that they were inadequate or ineffective, I think the 20's would have already been in the pipeline. Apparently you disagree.
yes, I was looking at those charts. and everyone that mentions the MG131 says it has a rate of 900rpm, but I beleive with the electronic syncronization (becouse the guns fired through the prop arc) it was reduced to around 810rpm. another thing none list a 13mm projectile which the MG131 used.This is one of those great "it depends" questions
yep. not a good idea at all. The MG 131 had a reliable explosive round which made it formidable and easily the 'match' of the M2 w/API. Two of those firing from the central axis of the 109 should be more effective than two M2 50's (of four or of six) on a Mustang. OTOH the two MG 131's together make up less than 30% of the firepower of a 109 (with Mg 151/20 motorcannon). As long as you have 20mm ammo the 131's provide some extra power. When this is depleted you better get your butt out of dodge. But if somehow you are forced to engage, two 131's w/ explosive rounds is still a lot better than two M2 w/API.I am not sure arming a plane with 6-8 MG 131s would have been a good idea if other guns were available.
I believe that one reason that some in the USN liked the 20 MM over the 50 cal was that their fighters were more and more being used for ground attack. In an air to ground role, shorter firing times were not as critical as they could be in the interceptor role. There was discussion during the Conference about, in the strafing role, the tendency of the pilots to hold down the trigger and burn out the barrels in one run, inadvertently of course. The slower rate of fire and shorter firing time of the 20 mm made burning out the barrels a little less likely, not to mention its greater destructive power.
One important factor to keep in mind was that as an interceptor or escort fighter, the airplane has only one reason to exist and that is to carry a weapon or weapons into the sky and shoot down E/A. A fighter in those roles is useless without ammo so long firing times were a big advantage. Interestingly though the Navy planes could carry a lot of ammo and their firing times were pretty high.
Another interesting point is that the throw weight per second of the F4U1C with four 20mms was 11.6 whereas the F4U1 with six 50s had a throw weight per second of 9.54. Not a huge difference.
To me, a useful analogy in this debate is a dove hunt. One dove hunter is equipped with a 12 gauge, improved cylinder and fifteen number six shells. The other is carrying a twenty gauge improved cylinder and has twenty five number 7.5 shells....... My bet is that the hunter with the 20 gauge is more likely to limit out. He can miss fifteen times whereas the twelve gauge man can have only five misses. To me, that is a smilar situation to the escort fighter or interceptor in fighter versus fighter ACM comparing the 20 mm to the 50 cal.
yep. not a good idea at all. The MG 131 had a reliable explosive round which made it formidable and easily the 'match' of the M2 w/API. Two of those firing from the central axis of the 109 should be more effective than two M2 50's (of four or of six) on a Mustang. OTOH the two MG 131's together make up less than 30% of the firepower of a 109 (with Mg 151/20 motorcannon). As long as you have 20mm ammo the 131's provide some extra power. When this is depleted you better get your butt out of dodge. But if somehow you are forced to engage, two 131's w/ explosive rounds is still a lot better than two M2 w/API.