Talk:Hispano-Suiza HS.404

Merging
I am not in favour - it would produce too large an article with diverging weapon histories. Can a rationale for merging be given? Saltmarsh 07:04, 8 October 2006 (UTC)

I am not in favour either; the Hispano cannon was of significance in its own right, especially considering the efforts made ny the US and the UK to improve the weapon during the difficult stages of WWII, and taking into account the uses to which it was put and the number that were manufactured. RG 14 October 2006

Oppose as per above. There were significant developmental and operational differences between these weapons Emoscopes Talk 19:45, 14 October 2006 (UTC)

Photos
The article hasn't any photo of this weapon.This site: [] has a photo of this weapon.Agre22 (talk) 20:28, 7 September 2008 (UTC)agre22
 * Not all images found on the web are acceptable in wikipedia; see Uploading_images. Bukvoed (talk) 08:29, 21 September 2008 (UTC)
 * Anyway, now this specific article does have some photos. Bukvoed (talk) 06:15, 22 September 2008 (UTC)

Comments please
The article states:
 * "When the projectile passes a port cut into the barrel, the hot gas enters a chamber where it presses against a piston., allowing pressure in the barrel to drive the bolt backward. Since the bolt was locked during firing, the heavy bolt of the Oerlikon could be replaced by a much lighter one, which greatly increased the rate of fire to 700 rounds per minute...."


 * The gas "presses against a piston" - ok.


 * "The piston is connected to a rod that unlocks the bolt" - more to it than that. The rod has two projecting lugs on its rear end (closest to the breech). They push on two slim rods that go rearward to in turn push against two slides, one each side of the breech block. They lock the breech block in place when the round fires, so when the slim rods unlock the block, gases from the breech force it rearward until it recoils against a spring to rebound forward, collecting a new shell from the bfm (belt feed mechanism) on its way. I'm guessing that where the article says "bolt" it means breech block, but whatever, I think we should include the information I have placed here. Moriori (talk) 03:59, 22 September 2011 (UTC)


 * I don't quite get the mechanical description here: Do the system of rods keep the block in place or do it unlock it? Per your description, the gasses (which I suppose are siphoned off the barrel) locks the block. In the current text, the gasses act on the system to unlock the block. Could you clarify? Petter Bøckman (talk) 11:27, 22 September 2011 (UTC)
 * Sorry if I wasn't clear Peter, but yes it is technical and confusing, especially at 700 rpm.
 * In a fighter aircraft fitted with the Hispano 20mm, each cannon had the pre-determined number of shells loaded into a dedicated ammunition "bay" (for want of a better word).
 * The belt of ammunition was fed down through a chute and connected into the top of the bfm (belt feed mechanism) which clicked in to firmly attach to the top of the weapon, directly over the breech block.
 * This meant there was a round of ammunition sitting directly above the breech block.
 * Before the aircraft transited to the end of the runway (or at the end of the runway), an armourer would cock the weapon by attaching an exterior cord to the breech block and pulling it rearwards, (sometimes over a pulley). The spring at the rear of the weapon returned the block slightly forward until it rested against the  sear, meaning the front of the block was just behind the rear of the shell.
 * When the pilot pushed the fire button, the sear released the breech block which the rear spring forced forward to collect the round at the bottom of the bfm.
 * The round was forced into the chamber, and a locking mechanism secured the breech block in place a split second before the round was fired. I am trying to be clear on this, but it is very technical.
 * Not quite half along the barrel and on top of it was what you described as a port. As the shell passed beneath it, the gases behind it went up though the port into a chamber to act on the piston on the front end of the "rod" you mentioned.
 * The enormous gas pressures force the rod rearward. It has two lug/cam thingies at the rear end of it. Each one of them forces two much smaller diameter rods back. They release the mechanism which was securing the breech block in position, meaning the residual gases in the barrel/breech instantly send the block way, way back until it hits the spring and is then propelled forward again to start the operation over.
 * I know this seems/is very technical. I think what we have now is inadequate, but am not sure how much to include. If there are crackerstackers hereabouts, maybe they can help. Moriori (talk) 09:10, 23 September 2011 (UTC)


 * This 1942 article in Flight describes the Hispano action - albeit possibly translated from a German description. GraemeLeggett (talk) 10:18, 23 September 2011 (UTC)


 * Not a problem, you description makes perfect sense. In short, the bolt is locked when it closes and during firing, and is only unlocked when the gasses siphoned off from barrel pushes a system of rods back, releasing the bolt. I've reread Chinn's description, and it appears a single locking lug was pivoted down into a recess in the receiver. The two rods you mention lifted this, allowing the gass acting onth ebolt head to drive it back. By then the gas pressure in the chamber/barrel has dropped to a safe level, but is still high enough to force the bolt back to cycle the mechanisms. I believe this is basically similar to the action in an M-16 Rifle, only with a rod and piston. I suggest putting the description of the mechanisms at the end, under the Properties section. Petter Bøckman (talk) 12:57, 23 September 2011 (UTC)


 * Description of operation belongs at the front, before describing the history of the variants - otherwise how is one to know what is being modified or changed. GraemeLeggett (talk) 14:08, 23 September 2011 (UTC)


 * You are right. I guess it belongs under the development heading. Petter Bøckman (talk) 15:32, 23 September 2011 (UTC)

This may be late in these entrees but the comment in the wiki about the caption showing the P38 lightning is in error, the P38 lightning did not house 20mm cannons in its nose and the picture clearly shows the loaders, installing .50 Caliber rounds, not 20mm, because the AN/M2 was the flexible .50 Caliber MG, The same used in most allied aircraft of the time. I highly doubt that all of the 20mm cannons in the american arsenal were Hispano-Suisa, but rather were Orelikons, but P38's main armament were four or more AN/M2 Browning Flexible .50 Caliber MGs! — Preceding unsigned comment added by AcadGlade (talk • contribs) 10:10, 25 January 2015 (UTC)

The P38 did have one 20mm cannon in the nose, Probably along the centerline of the aircraft, below the AN/M2 Brownings. — Preceding unsigned comment added by AcadGlade (talk • contribs) 10:41, 25 January 2015 (UTC)


 * The gun barrels in the picture are undoubted .50 BMG, but the shells are 20mm's. I have handled .50 calibre rounds, and they do not look like that. Additionally, the box from which the shells have been taken read "20 MM GUN". The caption from the original photo reads "1st Lt H. A. Blood examines ammunition for the single 20 mm M2 in the nose of a Lockheed P-38 Lightning". Petter Bøckman (talk) 15:24, 27 January 2015 (UTC)


 * Correct. I have changed it.Moriori (talk) 00:06, 28 January 2015 (UTC)

I'm just looking at the patent drawing of the gun's innards and I'm not seeing anything that suggests any sort of delayed blowback there: it looks to be a fairly standard positive-locking action not entirely dissimilar to that used by e.g. the FN FAL, a short-stroke piston pushing a bolt-carrier which unlocks the bolt, the pair of which are then carried backwards by the impetus. Okay, there are minor differences in that the HS404 uses a flap rather than tipping the entire bolt and its rearward impetus is perhaps augmented by the entire gun recoiling (again not unseen elsewhere: the Bren did something similar, for instance) but unless I'm missing something I'm not seeing the described delayed blowback in action. Am I indeed missing something or is that description misleading? --Vometia (talk) 00:39, 24 August 2018 (UTC)
 * Oh yeah, and the comment about residual gas pressure: there shouldn't be any. Think of how it is firing a blank cartridge for instance, it's absolutely recoilless (well, perceptibly, anyway) and without an adapter it won't cycle an action whether blowblack, recoil or gas-operated.  And the point is that there shouldn't be any residual pressure: if there were it would make the sides of the case stick to the wall of the chamber as much as pushing back against the base with all the risk of it tearing off resulting in a jam that would be impossible to clear in flight, and possibly damaging the gun in the process: which is exactly why it positively locks in the first place.  By the time the piston/carrier/bolt assembly are accelerated and moved to the point where they unlock, a combined mass very many times that of the projectile which has already accelerated up to much of its maximum velocity by the time it passes the gas port, the projectile will be long gone and the gas pressure mostly neutralised.  A short-stroke action can certainly give the impetus by itself if you think of e.g. a snooker ball which is only touched momentarily by the cue before ricocheting around the table causing chaos (well, when I play, anyway).
 * I was also somewhat ambivalent about including the recoil-assisted idea and still am: most likely, as with the Bren, it's more about making the recoil impulse less violent rather than contributing anything of worth to the action. --Vometia (talk) 13:10, 2 September 2018 (UTC)
 * It's been a while but I'm going to remove delayed blowback from its mechanism of action as it doesn't seem to be anything other than an impulse moderation feature. --Vometia (talk) 16:57, 13 March 2020 (UTC)
 * Admittedly I'm very uncomfortable going against a cited source though it doesn't say what its source is. Having read it, and this means little as it's just my own interpretation, the waxed cartridges/fluted chamber though often a thing with blowback operated weapons in this case seem to indicate an issue with primary extraction problems due to the chamber length.  But I'm just a layperson so I dunno.  --Vometia (talk) 17:04, 13 March 2020 (UTC)

Wait, one of these appears wrong...
This article states that gas operation allowed the bolt to be much lighter than the original FF's API blowback. However, the article on API blowback states that design allows the weight of the bolt to be halved. The comparison is not direct, and the "half of what" is not really explained, but generally this seems to be contradictory. One or the other article should be edited to improve clarity. Maury Markowitz (talk) 14:16, 22 February 2012 (UTC)


 * The bolt of an API blowback like the Orleikon is lighter than one in a simple blowback firing the same round. The gass opperation on the Hispano allows for an even lighter bolt as it is actually locked during firing. The MgFF too had a lighter bolt than the Orleikon, achieved by better construction and lighter charge. Petter Bøckman (talk) 19:45, 22 February 2012 (UTC)
 * Please add that into the article, it's very confusing as it is. Maury Markowitz (talk) 01:13, 6 March 2012 (UTC)
 * Check to see if it is better now. I have also edited the MG FF article for clarity. Petter Bøckman (talk) 10:24, 7 March 2012 (UTC)


 * Blowback with Advanced Primer Ignition fires the cartridge before the closing bolt has come to rest against the head of the chamber and so the recoil needs to stop the forward motion of the bolt first before it can then start to reverse it. So the bolt can be made lighter, as the initial inertia of the still forward-moving bolt has to be overcome first, making the bolt appear to the firing cartridge to be heavier than it actually is.


 * Blowback with API was used on simple SMGs such as the Sten. IIRC, blowback of both types tends not to be used for calibres over small arms sizes simply because the motion of extraction of the cartridge case tends to be violent, leading to detached rims and consequent jams. The only larger calibre guns to use blowback IIARC were a few Italian aircraft guns and the German MK108. Another disadvantage of either method of blowback for an aircraft gun is that the gun maintains an open breech all the time, and this leads to problems due to the intense cold at high altitudes, sometimes the breech lubricating oil or moisture in the air freezing and seizing the breech.


 * Gun jams on aircraft of the period tended to be more serious than others as a wing-mounted gun can not be cleared until it is back on the ground. This is why the British didn't use the US produced versions of the Hispano, as a stopped wing gun was useless until an armourer could clear it after the aircraft had landed. The other factor is that each 20mm cannon has a considerable recoil force and if a gun is stopped on one side of the aircraft the differing recoil forces caused by having two on one side, and only one on the other, firing, cause the aircraft to yaw away from the side with the stopped-gun and throw-off the pilot's aim. For a pilot of average abilities this can lead to a wasted sortie, with no hits on anything at all. So in these circumstances a gun that frequently jammed was far more of a problem than might otherwise be assumed. — Preceding unsigned comment added by 80.7.147.13 (talk) 09:52, 4 October 2012 (UTC)


 * BTW, the RAF went over to wing-mounted guns because fuselage-mounted guns firing through a propeller needed an interrupter gear which reduces the rate-of-fire of the gun. For the new monoplane fighters such as the Spitfire and Hurricane the RAF wanted the greatest firepower to be delivered in the shortest possible time, hence the eight wing-mounted guns.  — Preceding unsigned comment added by 80.7.147.13 (talk) 12:41, 20 January 2013 (UTC)

and wing guns were easier to produce and maintain, an interuptor gear just added extra weight and increaser production time, it would also mean modifications to the aircraft, this would have delayed the adding of cannons to Spitfires during and after the battle of Britain (213.167.69.4 (talk) 11:08, 5 September 2013 (UTC))

Magazine
22 lb (10.0 kg) (loaded 60-round M1 drum magazine) - there's probably an error. The weight of single 20x110 round is about 0,25-0,26 kg. So 60 rounds without magazine must weight about 15 kg and with magazine even more. 10 kg is probably the weight of empty (unloaded) magazine. — Preceding unsigned comment added by Speedy 13 (talk • contribs) 23:04, 24 December 2013 (UTC)

20x110mm
Why is there no article about the 20x110mm round? It was very widely used, and there is an article about the 20x110mm USN, so why not one for the standard round? Everything just directs you to the 20mm page. — Preceding unsigned comment added by .45Colt (talk • contribs) 00:48, 22 February 2014 (UTC)
 * Because unfortunately nobody has written one yet. Faceless Enemy (talk) 15:08, 29 January 2016 (UTC)

Spitfire Mk.V
The British section makes it sound as if the Hispano was first adapted for the Beaufighter, and then they wanted to use it for fighters, but "experimental" versions of it proved to jam too much, so they used 12-gun fighters until belt-feed was perfected, when they adopted it for fighters. That's not how it went. It's true that early experimental attempts to use it as a wing gun had reliability problems, but they managed to get past that enough that the Spitfire Mk.V used two drum-fed Hispanos and 4 .303 Brownings as standard, and it was a major variant. The 12 gun fighters were designed, but very few were made, relatively speaking (Hurricanes and Typhoons were the only ones, as far as I know, and only the 12-gun Hurricanes were actually made in any real numbers). The problem with the Mk.V's cannons wasn't reliability, but limited ammunition capacity. When they came out with the next versions, like the Mk.IX, they had developed a belt-feed mechanism and used it in all subsequent fighters. Perhaps there was reliability issues with the Mk.V installation, but I've never heard of them; I only recall reading that the very first experimental attempts had problems, which is why they didn't use cannon UNTIL the Mk.V. I definitely remember that it suggested that they had ironed out the problems enough to allow them to use cannons for the Mk.V. Either way, the Mk.V was definitely not an "experimental" fitting, it was standard armament, whether it had reliability problems or not. Also, it gives the difficulty of swapping magazines in the Beaufighter as an example of the reason they wanted belt-feed, but as far as I know, all Beaufighters used drums for the duration of the war (I'm not positive though; I was looking for some evidence that they ever did use belt-feed in Beaufighters, and that's how I ended up here). In any case, there were probably a lot more two-drum-fed Hispano armed RAF fighters made than 12-Browning fighters. It was much more than an experimental installation. Also, I notice that in the infobox for the American version, they give the weight for each component of the system, but no total overall weight. When you add the numbers up, it comes out to more than the weight given for the British version. Possibly the British weight is only for the gun, minus the ammo drum? Maybe something could be done with that? AnnaGoFast (talk) 05:35, 29 January 2016 (UTC)


 * IIRC, the first trials with Hispano-armed Spitfires were during the Battle of Britain where a few Spitfire Ia's (or perhaps III's) were so-modified however due to the Spitfire's thin wing the cannon had had to be mounted on their side due to the angle of the drum feed mechanism and this put additional friction on parts that were not designed for it and so jamming was frequent enough for the Spitfire's pilots to request normal .303-armed aircraft. This was an operational trial by normal squadrons, i.e., against attacking German aircraft, during the middle of a period of intensive fighting and so once not seen to be immediately usable the use of cannon was temporarily abandoned for single-engined fighters.


 * It was around this time - 1940 - I presume that the requirement for either 4 x 20mm or 12 x .303 was issued, as it was wished to increase firepower over that of 8 x .303 and as the Hispano trials had been inconclusive the new fighters built to this - the Hawker Tornado and Hawker Typhoon - both Hurricane replacements - incorporated provisions for either. In addition, the newest variants of the Hurricane, the II and the X, also included this provision, as did the Miles M.20 and IIRC, the Martin Baker MB3.


 * Once the Battle was over and in around 1941 it was possible to design a new breech feed mechanism that allowed installation right-way-up - IIRC - and so the Hispano II was then usable in the Spitfire V and subsequent Marks, first drum-fed, later belt. The installation was usually only for two guns, one per-side as the aircraft's radiator/hot air wing duct system only had sufficient heating capacity to heat one cannon per-side. This is needed to prevent the guns/cannon freezing up at high altitude. Later Spitfires had sufficient heating capacity for two Mk V cannon each side. Very few of the other 12-gun aircraft were built because by then the Hispano was reliable and had proved itself superior to the .303 and so most were built with 4 x 20mm.


 * I don't know if the Beaufighter always had drum-fed cannon but I seem to remember John Cunningham stating in his book that his gunner had to change drums for the guns in flight. I may be wrong though. The Mosquito had belt-fed Hispanos. The Whirlwind had drum-fed ones. — Preceding unsigned comment added by 95.150.100.255 (talk) 20:36, 19 April 2016 (UTC)


 * Video of 20mm Hispano being fired:  — Preceding unsigned comment added by 95.149.53.148 (talk) 16:37, 28 June 2016 (UTC)

Yaw
The article mentions that when a wing gun jammed the plane would then yaw towards the side with the failed gun. Surely this is the wrong way round, and if you have, say, a failed gun on the left wing then you would yaw to the right when you fired, as there's a recoil force acting back on the right and not on the left? Captain Pedant (talk) 15:00, 22 April 2017 (UTC)


 * You are quite right. Corrected. — Preceding unsigned comment added by 95.144.50.200 (talk) 11:46, 5 June 2017 (UTC)

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