P-47 Ait to Ground Role - Different Armament?

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Staff Sergeant
Feb 23, 2005
Should the eight .50 cal machine guns been substituted for a different set of guns after the P-47 assumed a primary role as ground attack fighter / bomber?
That is quite a subject for debate. I knnow a guy that was involved with testing the armor and armaments on the P-47 during the war. He said they tested the 20mm and the damage wasn't that much different with the .50 calibers. The big advantage is that you could carry more ammo with the .50.
I seem to recall that the U.S. Navy did some experiments on the effectiveness of the .50 cal vs. the 20mm. They concluded that round for round, the 20mm had 2 to 2.5 times the effectiveness of the .50.

Pursuant to this, the Navy switched to 20mm's at the end of the war and from thereon.

I think the P-47 could have been outfitted with six 20mm's and still been able to carry 175 rounds per gun. Six 20mm's would have been pretty devastating.
Well, I am going by what I heard from someone who tested the new systems during the war. What he didn't specify was what they tested the guns against. In air to air, it probably wouldn't have made a huge difference. Air to ground might have been another story. But they did switch to the 20mm for the Corsair for Korea, so I should see if Joe could clarify what they were testing the .50 cal versus the 20mm with. I will have to look it up, but I think they did develop a P-47 with 20mm, but I don't think it was produced in quantity.
If they could install four 20mm's on a Hurricane, I don't think an extra set of 20mm's would be a problem for a Thunderbolt.
Why don't you think so?

The P-47 had significantly larger and more robust wings than the Hawker Hurricane and was a far more stable gun platform.
Sure the p-47 could have carried 6 x Hispano's, especially M3's.

The .50 BMG weighed about 30 KG, the Hispano II (or AN-M2) about 50 KG, and the Hispano V (M3) about 42 KG. So eight .50's weighed about 240 KG, 6 x AN-M2's about 300 KG, and 6 x M3's about 252 KG. There would be room for at least 200 rpg.

In actuality, they were considering a P-47 with 6 x 37mm guns on it, and the M10 37mm weighed a wopping 96 KG each, so 6 x 20mm's was certainly doable.

The 20mm would probably have been a good idea, but remember the Hs.II had almost 3 times the rate of unclearable stoppages as the .50 BMG. Also, all sides had problems with cannon freezing at moderate altitude (above 15-20K). This was especially a problem with the Hispano which fired from an open bolt - allowing cold air to rush through the barrel when it was not firing. On the F4U-1c, guns would almost always freeze above 15,000 feet, despite the presence of electric gun heaters. Spitfires had problems with the Hs.II's freezing at altitude too.


RG_Lunatic said, " In actuality, they were considering a P-47 with 6 x 37mm guns on it,"

Six 37mm guns on the P-47? Where have you heard this? I know that a variant of the XP-72 was designd to have four 37mm guns.

Isn't there something in the Geneva Convention about that? :lol:
I cannot recall where I saw it, but I remember thinking it was absurd, and also that the US M4/M10 37mm was a crappy gun anyway. It was one of those wild ideas that went nowhere.

What I cannot understand is why the USA didn't simply neck up the .50 BMG to 20mm. It should have been easy to do (ala the Japanese Ho-5) and it should have been possible to maintain nearly 800 m/s, 800 rpm, and deliver a 90-100 gram HE round. No major changes were needed, just minor changes to the breech, barrel, and feed mechanism.


cheddar cheese said:
6 37mm's!? Wow :lol:

It was an absurd notion, the number was later cut to 4, and then never pursued. My point was simply that the P-47 could certainly mount 6 x Hispano's, especially the later short-barrel variety.

A more interesting armament would have been 8 x B20's or .50 BMG's necked up to 20mm.



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