Why no heavier RAF machine gun calibres? (1 Viewer)

Admiral Beez said:

I was referring to a .50 cal gun pod.

Click to expand...

And I was adding extra information.

The initial internal 20MM armed version of the F-4 was an modified RF-4C, with the gun barrel firing through the forward camera window. They were considering doing a production run of 100 but decided on the E model instead. I built an IMC 1/72 RF-4C as the cannon armed version.

Note that .50 cal gun pods were common, being used on the T-28A as well as the armed versions, T-28D, AT-28. And some AH-1's had 20MM gun pods.

Admiral Beez said:

Was a four .50 cal manned rear turret ever tried before the B-52? It would be a beast.

Here's the M45 Quadmount for scale.


View: https://www.youtube.com/watch?v=jfLEq2PrgME

Click to expand...

Hey Admiral, I'm not sure, to be honest, I can't find any record of the Brits designing a turret that could fit four fifties, although designs might have been drawn up, they certainly weren't built. The three main powered turret manufacturers, Boulton Paul, Bristol and Nash & Thompson all built 50 cal armed twin turrets. BP began their first in 1939. Bristol eventually went for 20 mm Hisso armed turrets, side stepping producing numbers of their fifty armed turrets altogether, whereas BP continued its development even after the Ministry of Aircraft Production told the firm to concentrate on .303-in armed turrets in 1940.

Clayton Magnet said:

The He 177 had a 4x 13mm machine gun rear turret, but I have no idea how many actually made it into service

Click to expand...

Not sure either, I think it was only experimental, Clayton and was fitted to maybe a few examples? Oddly, despite being a relatively sophisticated looking turret, it was manually operated.

gruad said:

I believe about 1,500 of 7,300 Lancs had twin .5 rear turrets introduced late 1944.

Click to expand...

I'm not sure but the .50 cal armed rear turrets were not in large proliferation on service aircraft until they were fitted as standard to Mk.VII Lancs. Canadian built Mk.Xs received Martin 50 cal armed mid upper turrets, which accounts for a significant number of 50 cal armed Lancs, but they still had .303 armed four gun rear turrets. 50 cal turrets might have been retrofitted to numbers of Lanc Mk.IIIs, but you have to remember that Lancaster production did not end immediately when the war ended, and the majority of the Lancasters in service in 1944 and 1945 still had .303 armed turrets as they had done in 1941. The French navy Mk.Is that they received post war were modified to resemble the Mk.VIIs they received that were fitted with twin 50 cal rear turrets. Mk.VIIs also received Martin 50 cal armed top turrets like the Canadian Mk.Xs.

gruad said:

This was one of the great frustrations of Bomber Harris in that he fought to get the 5 turret and industry didn't seem to respond.

Click to expand...

It wasn't industry that didn't respond. All the British power turret manufacturers developed .50 cal armed turrets during the war, Boulton Paul began development of .50 cal armed turrets in 1939 and had working turrets less than a year later. It was MAP who stifled development, insisting on producing .30 cal armed turrets in the name of expediency, although the turret manufacturers continued developing 50 cal armed turrets so that when the need arose they were available and didn't require extensive development.

Admiral Beez said:

Was a four .50 cal manned rear turret ever tried before the B-52? It would be a beast.

Click to expand...

Yes, the G-model had a remote 4x.50. We had some of those at Moron for Desert Storm, from Griffiss and K.I. Sawyer bases on deployment. We had no H-models (M61 Vulcan in the rear barbette) at Moron, which is what my home base flew.

B-52G:



B-52H:



The D-model had quad-.50s as well, and I'm pretty sure it got at least one kill if not more against NVAF MiG-21s in 1972.

D-model, note aircrew accommodation and not remote operation:

Thumpalumpacus said:

Yes, the G-model had a remote 4x.50. We had some of those at Moron for Desert Storm, from Griffiss and K.I. Sawyer bases on deployment. We had no H-models (M61 Vulcan in the rear barbette) at Moron, which is what my home base flew.

Click to expand...

Very cool! Of course the B-29 and P-61 had power turrets with four 50s fitted, although only the forward upper turret on the B-29 had four guns.

nuuumannn said:

Very cool! Of course the B-29 and P-61 had power turrets with four 50s fitted, although only the forward upper turret on the B-29 had four guns.

Click to expand...

Right, but the airframe on the -52 could accommodate a radar specifically for the stinger. B-29 perhaps, I don't know, P-61, probably organic for the entire plane rather than the turret itself. But if you look at the pics above, the -52 had radar specifically for the stinger aside from anything else. Not sure it came to much after 1972, but hey -- 4th on my dreamsheet enlisting in 1989 was B-52 tailgunner ... nods to my gramps.

Shortround6 said:

There was also a problem with the fuses in the early ammo being much too sensitive and exploding on impact with the aircraft skin and not penetrating,

Click to expand...

Shortround6 said:

There was also a problem with the fuses in the early ammo being much too sensitive and exploding on impact with the aircraft skin and not penetrating, solve in short term by mixing in solid (or hollow) inert training rounds which would penetrate quite a bit but not do anything else. I don't know when they got the fuse thing straightened out.

Click to expand...

The successor fuse still remained a superquick, instantaneous fuse intended to explode on impact.
The only changed was from a more complicated to a cheaper concussion fuse (which then was increased in sensitivity through its development to lower the chance of a dud in case of a shallow strike angle or too low velocity).
It took about 45-40 micro seconds till shell rapture upon impact.
With its 5.6grams of Tetryl (~7grams TNT equivalent) it also held not that much explosive filling
The Germans where the only ones who intentional deployed a delay charge for the mine shell to take advantage of the blast and pressure effect inside the stressed airframe structure of "then" modern planes

Yew Staff said:

With its 5.6grams of Tetryl (~7grams TNT equivalent) it also held not that much explosive filling

Click to expand...

Shortround6 said:

I don't know when they got the fuse thing straightened out.

Click to expand...

The short version is:

(1939) No.252 fuze: original French design - too sensitive
(1941) No.253 Mk.I fuze: striker mechanism removed - only operates when striking a sufficiently sturdy object (petrol tank, spar, etc.)
(1942) No.253 Mk.II fuze: thinner end cap - increased sensitivity
(1943) No.254 fuze: booster cap and tetryl pellet being replaced by a six grain lead azide/tetryl detonator

re: the lower HE charge, in testing it was found that the HE/I round was
- more destructive than a pure HE round (10.2g tetryl) due to a greater number of effective (larger) shell fragments
- more effective as an incendiary than a pure incendiary round (presumably due to the greater distribution of filling)

Thumpalumpacus said:

ot sure it came to much after 1972, but hey -- 4th on my dreamsheet enlisting in 1989 was B-52 tailgunner ... nods to my gramps.

Click to expand...

On the G and H models the gunner sat up front with the other guys, while on the earlier models he was back there in the tail. I once found myself searching the rear fuselage of a B-52G, looking for the tail gunner compartment to address a pressurization problem. I had been told by a senior engineer it was a D, and I just assumed the reason it did not look like my Monogram B-52D was because they had done a lot of mods. They had taken off the vertical tail so it would fit in the hangar, so the taller tail of the D was not a recognition feature.

And yes, some models of the B-29 had a radar for the tail gun.

MIflyer said:

On the G and H models the gunner sat up front with the other guys, while on the earlier models he was back there in the tail.

Click to expand...

Right, and I knew that when enlisting. I still liked the idea of shooting back.

nuuumannn said:

Very cool! Of course the B-29 and P-61 had power turrets with four 50s fitted, although only the forward upper turret on the B-29 had four guns.

Click to expand...

Did the B-29 forward upper turret have a selector switch to fire two guns or all four guns?

Alan Stevens said:

Did the B-29 forward upper turret have a selector switch to fire two guns or all four guns?

Click to expand...

Donno. Look at this. Also note the B-29 gunners document attached.

To quote the estimable A. G. Williams "
Vickers was in the process of developing a scaled-up version of their .303" MG, chambered for a new .5" (12.7 mm) cartridge. This was produced in three versions for army, naval and aircraft use and was tested by the RAF in the mid-1920s against the new .50" Browning heavy machine gun, which was bigger and more powerful. The conclusion was that neither offered sufficient advantages to replace .303" MGs, since the slightly bigger hole they could punch wasn't adequate compensation for their greater size and weight and their lower rates of fire. The Swiss Oerlikon 20 mm cannon, developed from the German Becker of the Great War, was also tested in the late 1920s and early 30s and proved more promising since its explosive shells could do a lot more damage than just punching bigger holes, but it was big, heavy and slow-firing.



As a result of all of this, the RAF decided in the mid-1930s to stick with the .303" calibre for the time being, while noting that a 20 mm gun would be the preferred replacement if armour protection were applied to warplanes. After competitive tests, two new machine guns were selected; the US Browning and the Vickers Gas Operated (known also as the VGO or Class K), a modification of the Vickers-Berthier light MG. The Browning was considerably modified over the American original. It was not just converted from .30 to .303 inch calibre but also modified to fire from an open rather than a closed bolt because the cordite-loaded .303 rounds tended to explode if left in a hot chamber. The Browning was belt-fed and initially intended for fixed fighter installations (although later adapted for use in turrets). In contrast the VGO used a pan magazine of 100 rounds and was for flexible mounting. It bore a close resemblance to the Lewis, although internally it was quite different. Rates of fire were around 1,200 rpm for the Browning, 950 rpm for the VGO. It was with these weapons that the RAF fought the Battle of Britain."


Vickers was in the process of developing a scaled-up version of their .303" MG, chambered for a new .5" (12.7 mm) cartridge. This was produced in three versions for army, naval and aircraft use and was tested by the RAF in the mid-1920s against the new .50" Browning heavy machine gun, which was bigger and more powerful. The conclusion was that neither offered sufficient advantages to replace .303" MGs, since the slightly bigger hole they could punch wasn't adequate compensation for their greater size and weight and their lower rates of fire. The Swiss Oerlikon 20 mm cannon, developed from the German Becker of the Great War, was also tested in the late 1920s and early 30s and proved more promising since its explosive shells could do a lot more damage than just punching bigger holes, but it was big, heavy and slow-firing.

As a result of all of this, the RAF decided in the mid-1930s to stick with the .303" calibre for the time being, while noting that a 20 mm gun would be the preferred replacement if armour protection were applied to warplanes. After competitive tests, two new machine guns were selected; the US Browning and the Vickers Gas Operated (known also as the VGO or Class K), a modification of the Vickers-Berthier light MG. The Browning was considerably modified over the American original. It was not just converted from .30 to .303 inch calibre but also modified to fire from an open rather than a closed bolt because the cordite-loaded .303 rounds tended to explode if left in a hot chamber. The Browning was belt-fed and initially intended for fixed fighter installations (although later adapted for use in turrets). In contrast the VGO used a pan magazine of 100 rounds and was for flexible mounting. It bore a close resemblance to the Lewis, although internally it was quite different. Rates of fire were around 1,200 rpm for the Browning, 950 rpm for the VGO. It was with these weapons that the RAF fought the Battle of Britain."

(A. G. WIlliams, RAFHS 08)
The important thing is that the RAF did look at heavy machine gunds, and found them to insufficiently superior to the 0.303" to bother. Pre-WW2, armor (although it had been used on WW1 aircraft, then abandoned. Go figure) was rare on combat aircraft. This means the greater penetration of the HMG was pointless, and the greater damage per round was more than offset by the lower rate of fire.

I don't think the RAF made a mistake in jumping past medium caliber machine guns; I think their mistake was in not putting more effort (money) into making the 20 mm work earlier than historical. Of course, it's easy to say this 80 years after the fact.

MIflyer said:

Donno. Look at this. Also note the B-29 gunners document attached.

Click to expand...

Good read! Still don't know for sure.
I figured that two guns would suffice in many cases given that they are dealing with fighters.
Head on attacks would face upper and lower forward turrets.
Save ammo when possible.

I suspect if the fighters want to shoot your ride from under you, you would use all four.
What good is the saved ammo if you are in flames?

special ed said:

I suspect if the fighters want to shoot your ride from under you, you would use all four.
What good is the saved ammo if you are in flames?

Click to expand...

By the time the B-29 shows up, most of the interceptors are carrying at least some cannon. Some were trying to ram on occasion.

Shortround6 said:

By the time the B-29 shows up, most of the interceptors are carrying at least some cannon. Some were trying to ram on occasion.

Click to expand...

I just figure it would be good to have the option. If the gunner determined that two guns could polish off the fighter, then he could use that.

If he felt the need for all four when facing a group of fighters, then he could select that. Plus the CFC system can put more than one turret in the hands of one gunner.

Consider, if the Computer system worked against a target at a 400= MPH closing speed. then all of the B-29 losses would be from flak or mechanical failure.
I know if I was behind the sight, I would use all the guns I had to protect my crew and save nothing.

Well, consider that both the Axis and the RAF's biggest problem was shooting down enemy bombers. Bombers are offensive weapons and the offensive part of the war for the Axis did not last long after the US got in. After the Midway timeframe the Axis was increasingly looking fearfully at the horizon and after the Solomans timeframe that was all they were doing.

So the main target for US fighters for most of the war were not bombers, and certainly not heavy bombers, but instead fighters and dive bombers. The .50 was better for that than the 20MM, ESPECIALLY after the API round came out. You throw out a hellava more rounds with .50's than 20MM, thus enabling more hits during those fleeting sight pictures of fighter vs. fighter combat. For Korea we were faced with the prospect of fighting tougher, jet powered fighters operating at altitudes where things did not burn easily and 20MM was much better for that situation. For Air Defense Command in the 50's the main threat clearly were large bombers armed with nukes, so they went to 20MM and then to missiles. Vietnam forced a rethink of the problem of fighting fighters in genuine dogfights and the 20MM came back to supplement missiles. The F-15 was supposed to use a Gattling gun with 25MM caseless ammo but did not, and subsequent combats have focused almost exclusively on missiles, the gun being only a "nice to have" if you look at the stats.