British:
- not giving the .50 HMG a try was a mistake IMO, so this time around they should've try it - there is no reason that each Hurricane and Spitfire already by 1938 could not be armed with 4 HMGs, that each weapon is at least an equivalent of the Italian HMG; the HMG will also be a much better self-defense weapon than a LMG of the era
This may be nit picking. British .5in ammo came in two types. The .5in Vickers, rather widely used, both Semi-Rimmed (export/license) and Rimless (British use) and the .5in High Velocity or class D. Once you add the "0" into the designation you are talking about the .5
0 Browning
Now for the British in 1938 that means either buying/licensing the the Browning gun and adapting it to use different ammo or using the pretty much the standard US .50 Browning
as is.
Which is the quick and easy way. Which means using the pre 1940-41 ammo let alone the M8 AP copied from the Soviets (?).
The only other .5in guns in
service existence (not experimental) in 1938 were two Italian guns and the two British Vickers guns and one Soviet gun (the 12.7mm ShVAK), the 12.7mm Berezin was not ordered into production until 1939 and actual production guns showed up in April 1941(?)
The British had no desire to use the Vickers guns in aircraft in locations where the crew could not reach them which rather limits the choice of exiting guns outside of the Soviet Union to the American gun (or Belgian license) and the Italian guns. The Breda-SAFAT or the Scotti, and the Breda-SAFAT weighed the same as the US Browning while using a less powerful cartridge although it did fire a bit faster. 700rpm instead of 600rpm or a bit under.
The Ammo in the British .5in Vickers B and the Italian guns had about the same velocity as the American gun/ammo but the American gun/ammo used heavier bullets. About 29% heavier than the British .5in Vickers ammo.
In 1938 the ".50" cal armament may have been a bit better than the eight .303s but not by much. The problem is that it is heavier and with the 1938 Hurricanes using two pitch props (forget the fixed pitch) that is a problem. Each American .50 is 2.8-2.9 times as heavy as the American .50 and more importantly, the 334 per gun ammo load of the Hurricane is only enough for just under 150rpg for four .50 cal Brownings. Going to 200rpg adds 60lbs and the change of guns adds about 40lbs. Maybe you can make up some of that with just using 4 mounts and not eight even though each mount is heavier?
You don't have higher velocity for better deflection shooting (that shows up in 1940/41).
You don't have good incendiary ammo (Neither does the .303 at this point).
You are only firing about 40 rounds per second, at best, compared to the 144-160 of the eight .303s (faster firing .50 cal Browning also show up in 1940-41)
You have within 1-2 seconds of firing time depending on ammo load out.
Now a late 1941/early 42 Hurricane with four late 1941/Early 42 M2 Brownings has got both the higher velocity rounds and the higher cycle rate guns. US had incendiary ammo but the British didn't use the American incendiary ammo until the M8 showed up later. And in 1941 you have the constant speed props and the Merlin XX engine which means a few hundred extra pounds of guns/ammo is less of a problem.
- as a step up - buy 20mm guns at Oerlikon for the RAF, too, not just for Army and RN; T. WIllians favored (and he still is, if I'm not mistaken) the FFL - again, the Oerlikons should've been available earlier than the Hispano
The 20mm Oerlikon guns were in a state of flux in the 1930s and Oerlikon was not actually shipping guns by the hundreds. Exactly when they hit the published rates of fire with the different guns may be questioned?
Hispano got into cannon business because Oerlikon could not deliver they guns fast enough to equip the French (D 510s?) and they saw room for improvement in the rate of fire.
You can get Oerlikons sooner than you can get Hispano's but are you getting the newest, fastest firing versions?