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Browning .303 early Spitfire gun (pre-war) question


JMChladek

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I've got a slight issue I need help with. I'm steadily working along on my Airfix Spit Mk 1 with Watts 2 bladed prop and I see that the birds from 1939 to at least the early fall of 1940 had protruding flash suppressors on the outer wing guns, at least before the red arming tape covers were added in early 1941. I've done web searches for .303s with flash suppressors and they look to be cone shaped. But the Spit suppressors I've seen in pictures from the 1939-40 period (assuming they are suppressors and not some other housing) seem to look more cylindrical in shape.

So I am scratching my head a little here. I can't necessarily leave them off as they are a rather prominant feature on Spitfires from the pre-war period.

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Unwin's armourer tells how, just after the start of the war, he, and another man, went to collect new guns, for fitting in all of the aircraft; the suspicion is that this might have seen the end of the flash eliminators.

Edgar

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I've got a slight issue I need help with. I'm steadily working along on my Airfix Spit Mk 1 with Watts 2 bladed prop and I see that the birds from 1939 to at least the early fall of 1940 had protruding flash suppressors on the outer wing guns, at least before the red arming tape covers were added in early 1941. I've done web searches for .303s with flash suppressors and they look to be cone shaped. But the Spit suppressors I've seen in pictures from the 1939-40 period (assuming they are suppressors and not some other housing) seem to look more cylindrical in shape.

So I am scratching my head a little here. I can't necessarily leave them off as they are a rather prominant feature on Spitfires from the pre-war period.

The main reason for the removal of the long flash suppressors was because the guns were freezing and failing to fire at high altitude during interceptions. Heat was already provided to the guns (hot air ducted from the radiator I believe) through internal wing ducts but with the barrels always open to the elements this was innefective.

The solution was to redesign the flash suppressors to ensure the gun muzzles did not project from the leading edge, and introduce the gun patches. These, by sealing the gun ports stopped the guns overcooling, and enabled the gun heating system to be effective. I beleve that initially patches were also placed over the case ejection ports on the underside of the wings as well.

Selwyn.

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Supermarine talk of "covers" for the gun tunnels and empty case chutes, which were replaced (by them, possibly following the RAF's lead) by fabric patches in late September 1940. So far, I've no idea what those "covers" were.

During early cannon trials, rubber covers (not the medical/sexual sort) were tried, but rejected, because the cold affected them, causing them to become hard, and break up, with the likelihood of pieces entering the barrel, and causing trouble, so they couldn't be re-used very often.

An extra complication was having the guns cocked, consequently with the breeches open, thus even more susceptible to freezing, so the IIb & Vb had the facility for the pilot to cock the guns from the cockpit; the eventually redundant pipework can be seen in Hasegawa's 1/32 Vb kit, and in the Pilot's Notes for the IX.

Edgar

Edited by Edgar
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A) The story I learned was that the patches over the gun ports kept debris out, and also was an indicator of wether or not the weapons had actually operated or not helping the armors to trouble shoot a/c coming back from combat.

B) Browning machine guns operate on the " blow back " principle,weapon is cocked,round in the chamber, breach CLOSED. Trigger is pulled, the internal hammer strikes the firing pin located in the breach block, and fires the weapon. The pressure from the fired round opens the breach block, and strips out the empty case.The recoil spring forces the breach block forward, chambers another round, CLOSES the breach block, and the weapon fires again....as long as the trigger is pulled, it will continue to fire. So, how the cold air got into an open breach is a little impossible.... cold air getting up into the receiver thru the spent case chute is entirely possible, hence, taping off the openings.

Scott J

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A) The story I learned was that the patches over the gun ports kept debris out, and also was an indicator of wether or not the weapons had actually operated or not helping the armors to trouble shoot a/c coming back from combat.

B) Browning machine guns operate on the " blow back " principle,weapon is cocked,round in the chamber, breach CLOSED. Trigger is pulled, the internal hammer strikes the firing pin located in the breach block, and fires the weapon. The pressure from the fired round opens the breach block, and strips out the empty case.The recoil spring forces the breach block forward, chambers another round, CLOSES the breach block, and the weapon fires again....as long as the trigger is pulled, it will continue to fire. So, how the cold air got into an open breach is a little impossible.... cold air getting up into the receiver thru the spent case chute is entirely possible, hence, taping off the openings.

Scott J

Scott Edgar is correct. the Brownings used by the RAF were modified to operate differently to the original design. When the gun stopped firing the Breech blocks were held to the rear to cool the breech.When the trigger was released the breech block moved forward taking the next round from the belt and fired.

Selwyn

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Scott Edgar is correct. the Brownings used by the RAF were modified to operate differently to the original design. When the gun stopped firing the Breech blocks were held to the rear to cool the breech.When the trigger was released the breech block moved forward taking the next round from the belt and fired.

Selwyn

Selwyn is entirely correct: the British Brownings were modified so that the breech stayed open at the end of the firing cycle.

Please note that they are not blow-back weapons but rather they operate on the short-recoil principle: the breech is locked at the time of firing, unlike blow-back weapons which fire from an unlocked breech.

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