autogun

Military Guns and Ammunition

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This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.

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The Foresight War Revisited: Air Forces   Novel: The Foresight War

Started 16-Feb by autogun; 2558 views.
In reply toRe: msg 1
autogun

From: autogun

18-Feb

Engines: So far I'm not proposing any change to the original TFW proposal to concentrate on the Merlin and Hercules engines. Both engines were historically developed to produce over 2,000 hp, which is enough until turbines become available. Where jets are concerned, I would also continue to back both horses, with one company focusing on Whittle's centrifugal designs and another on the axial flow type.

Armament: here I have changed my mind. The original TFW proposal was to get FN to develop a compact Browning HMG around the Vickers 12.7 x 81 round (as in the Japanese Ho-103) to plug the gap between the .303 Browning and the 20mm Hispano.   However, I have gone off the Hispano: it was too late when it was needed most (the BoB) and was always an awkward beast not well suited to wing or turret mounting. So I would choose an Oerlikon instead - at about the same time as the British were being shown the Hispano (much more impressive performance than the early-30s Oerlikon), Oerlikon were thoroughly revamping their aircraft guns to reduce weight and increase their rate of fire. These guns had been developed for years, and could have been bought off the shelf in good time to equip RAF fighters before the war (with a belt feed being developed in parallel). 

The question is: which Oerlikon? There were three performance levels, all of them firing the same 128g HE shell: the FF (20 x 72RB, 600 m/s, 500 rpm, c.24 kg); FFL (20 x 101RB, 750 m/s, 490 rpm, 33 kg); and FFS (20 x 110RB, 830 m/s, 470 rpm, 39 kg). For comparison, the Hispano Mk II fired a similar shell at 880 m/s and at 600 rpm,  but weighed 50+ kg (it needed a strengthened mounting, which was extra). The RAF was originally interested in the biggest Oerlikon (the RN and USN bought a heavy-duty AA version firing the same ammo), but the FFL has some advantages, in that the MV and trajectory were very similar to the .303 Browning, helpful in mixed-armament installations, and the Japanese showed that the gun could be speeded up to 620 rpm (and 720 rpm right at the end of the war). Later, a streamlined M-Geschoss Ausf.C type of shell would reduce the weight and boost the MV. The light weight and low recoil would also be valuable. 

So, I'd go for the Oerlikon FFL initially, but in parallel with that start developing a more advanced and powerful gun of 25mm calibre. Not a Hispano type or a revolver, but a Gast twin-barrel job (the British had an example of the Gast MG to study). A RoF of around 2,000 rpm should be feasible initially, with the ammo firing a 200g shell at 900 m/s. 

Red7272

From: Red7272

21-Feb

autogun said:

but the FFL has some advantages, in that the MV and trajectory were very similar to the .303 Browning, helpful in mixed-armament installations,

Good choice. 4 guns initially and 4 guns with belt feed and improved rate of fire later. I suspect the 303s were a sop to their ego more than being useful. It might be simpler to stick with 20 mm so the pilots return rather than poke about with an inadequate armament.

autogun

From: autogun

22-Feb

There was a practical benefit of mounting a couple of .303 Brownings alongside the cannon, especially before a belt-feed was introduced (so the wing-mounted cannon were limited to using 60-round drums): one .303 could be loaded with the B Mk IV day-tracer/incendiary, which left a smoke trail all the way to the target, while another could be given the Dixon incendiary which ignited on impact, the bright flashes indicating hits. So the pilots could open up with the MGs and not fire the cannon until the .303s were hitting, thereby saving cannon ammo.

hobbes154

From: hobbes154

23-Feb

For the Germans, what about drop tanks for the 109 in the BoB and Norway?

Red7272

From: Red7272

23-Feb

autogun said:

There was a practical benefit of mounting a couple of .303 Brownings alongside the cannon, especially before a belt-feed was introduced (so the wing-mounted cannon were limited to using 60-round drums): one .303 could be loaded with the B Mk IV day-tracer/incendiary, which left a smoke trail all the way to the target, while another could be given the Dixon incendiary which ignited on impact, the bright flashes indicating hits. So the pilots could open up with the MGs and not fire the cannon until the .303s were hitting, thereby saving cannon ammo.

The Oerlikons fire slower so they get about 8 seconds. They have a much better tracer than 303 and hitting is not in doubt because of the explosions and bits flying off the target aircraft.

autogun

From: autogun

24-Feb

hobbes154 said:

For the Germans, what about drop tanks for the 109 in the BoB and Norway?

Yes, that sounds reasonable. I know that they did use these at some point, but obviously later. Anyone have any stats on the extra range they provided?

autogun

From: autogun

24-Feb

Red7272 said:

The Oerlikons fire slower so they get about 8 seconds. They have a much better tracer than 303 and hitting is not in doubt because of the explosions and bits flying off the target aircraft.

That would certainly work for the good shots, but most weren't... and could use up much of their ammo supply in trying to get on target.

Red7272

From: Red7272

24-Feb

autogun said:

That would certainly work for the good shots, but most weren't... and could use up much of their ammo supply in trying to get on target.

But do twice as much damage when they are on target. 

autogun

From: autogun

24-Feb

Red7272 said:

But do twice as much damage when they are on target. 

True - there are rarely any simple answers, just more or less good...

tomo_pauk

From: tomo_pauk

8-Mar

Excellent choice with Oerlikon; probably the FFL is the best choice of those for the RAF (not too heavy or bulky, slender ammo so more can be stocked vs. the S gun or Hispano, better ballistics than FFF). People at Oerlikon should start doing the belt-fed version ASAP, while concurrently making a version with better RoF.

Engines (UK) - indeed, Merlin and Hercules are the winning tickets. This probably means killing off the Vulture, Peregrine, Exe, and Taurus, so the two mainstream engines can be had both in quantity and quality? I'd also suggest RR start to do the design of Griffon (whether as a militarized 'R' engine - a quickest way - or a spin-off from it).

British might start making the pressure carburetors for their engines instead of float-type carbs, for better performance (10 mph and extra 1500 ft on Spitfire V), no propensity for easy ice build-up and no cutting at negative G.

Internal bullet-prof glass, vs. external BP glass for more speed.

Drop tank for Spitfire and other fighters (also for defensive scenarios), probably the best ratio is 1:1, fuel in drop tanks vs. internal fuel. For ferrying, the drop tank fuel can grow beyond that ratio.

You've already in TFW 1.0 killed a lot of dead wood (Botha, Defiant, Roc), that's a good thing.

Germany: Stock up the fuel until the eyeballs.

I'd strongly suggest that 2-engined 'day' fighters are not made. Drop tank for Bf 109E. Streamline it a bit (retractable tailwheel, stronger tail so the exeternal bracing can be removed). Fw 190 as a DB 601 powered fighter in service in 1940.

Water-methanol injection, so the lack of hi-oct fuel can be circumvented.

Guns: a belt-fed MG FF ASAP; Bf 109 has a small wing, size of a gun & ammo load matters much more than in Spitfire, let alone in Hurricane. A lighter shell for better MV, before the Mine shell emerges? Make a gun around the 23mm Madsen ammo instead of MG 151. Make the 'MK 105' - 30mm cannon firing the 330g shell at 700-750 m/s (= mid-way between MK 108 and 103).

Engines: Aero engines have the #1 priority for supply of nickel. Have Bramo and Avia (in former Czechoslovakia) making DB 601 engines from 1939, have BMW making jet engines from 1941 (= no BMW 801).

No Jumo 222, 213, no DB 603.

A real 'Schnellbomber' with a proper bomb bay - basically a German Mosquito, not the Ju 88.

1-engined jet fighter, 2-engined jet bomber and 2-engined night fighter for 1942.

Guided AA missiles (go simple there, even wire-guided short-range missiles), proximity-fused AAA ammo and missiles.

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