GregP
Major
Found that in a WWII document. Use a different weight if you want to.
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
IIRC the only issues re: 20mm armament for P-51s were a.) AAF always said no thanks, and b.) the original wing spar for XP-51F/G/J/H needed more opening space to accomodate the Oldsmobile Hispano. While I know USAAF considered 20mm or the P-51F, the spar was mentioned as an 'affected' assembly.Problem was US made HS404s rarely worked as intended, though US makers never adopted the shortened chamber that solved most of the issues that the British initially had.
Of course, on secretprojects I've read that the USAAF wanted eventually to mount 4 20mm cannons on the P-51H and the P-82B/XP-82, but NAA said "nope". Of course, if there's any truth to that on either end, I can say that NAA did propose armament fits for the P-51 and A-36 that included 20mm and 37mm cannons or a mix of the two, per several posts made my drgondog when discussing Mustang armament fits. But each time NAA proposed anything other than .50s, the USAAF ignored them.
Thus if the USAAF wanted 20mm cannons on the P-51H or the P-82B (due to both aircraft's potential as interceptors with 5000+ fpm climb rates on normal max take off weight and WEP), and NAA told them no (story is that NAA spec'd out for 6 .50s on both planes already when the USAAF suggested it), North American had been burned before on doing such work expecting/hoping the USAAF would come around to the cannon armed P-51.
And yes, If you've read the chapter about the P-51H in Michael O'Leary's book "Building the P-51 Mustang", there were mock ups of the NA-117 (pre-production P-51H design, production models were the NA-126, with the P-51L being the NA-129), there's photos there (as well as probably in Boeing's archives, and maybe someone else's archives) of a P-51H mock up with 4 20mm cannons.
I believe that the two images with 20mm provided by O'Leary are of the XP-51F 20mm mock up.I've seen photos in Building the P-51 Mustang that shows the NA-117 mock up (pre production P-51H) with four cannons in each wing. But one, it was a mock up, and two, it was the NA-117, which evolved into the NA-126 (production P-51H), which though very similar, I doubt that the NA-117 and NA-126 were completely identical Thus, what were the notable differences between the NA-117 design and 125
Not a real issue.Kind of OT, but I do remember reading that the LW-based P-51s would've needed an altered front wing spar to accommodate 4 20mm cannons. Would such changes have needed to be made to the earlier wings, given that the Mustang IA had 4 20mm cannons, and it was looked at as armament for the A-36 as well as 37mm cannons (albeit in underwing mounts for the latter--I saw that in the book)? Or even for the F-82? I wonder what such an armament arrangement would've looked like in both cases (maybe like the CA-15's arrangement?):
View attachment 762580
Source: Internet find, possibly from a document posted here.