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Sealing of BoB RAF gun muzzles


CliffB

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I know that the muzzles of wing mounted BoB RAF machine guns were sealed with red tape prior to flight - but what about the muzzles of turret mounted guns?

I'm thinking particularly of the belly-pack guns on my Blenheim 1f.

Many thanks

Cliff

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The sealing was primarily to prevent excessive cooling of the guns (especially at altitude) as the Brownings were an open breech type weapon. Rear facing guns wouldn't have the wind rushing through them so wouldn't need sealing. Not sure about front facing turret guns.

I would expect belly pack guns to need sealing, but it would depend on their type and the spent cartridge collection system. If there was no external ejection of cartridges then there wouldn't be any holes for the wind to flow through and sealing would be less necessary.

DP

Edited by Detail Police
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Not wishing to add too much to the mix...

An armourer i once chatted with told me it also served to show that the guns had been fired..and if there had been a jam. also...it served as a visual cue that the guns were armed, as they put the doped patches on after cleaning, loading etc.

he also said he didn't know what effect they had on gun heating...but it kept crap out of the muzzles..especially on muddy, damp grass fields...and in the desert, obviously.

He also told me, they used to put condoms over the muzzles of the 20mm cannon on the later marks.

Phil.

Edited by CornishRebel
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The sealing was primarily to prevent excessive cooling of the guns (especially at altitude) as the Brownings were an open breech type weapon. Rear facing guns wouldn't have the wind rushing through them so wouldn't need sealing.

DP

Yes,but more to prevent cold air rushing through the armament bays, in which the weapons were heated by ducted warm air,rather than through the weapons themselves.

Don't forget that the machine guns were cocked in the wings by the armourers so a nice newly applied patch might serve as a warning not to walk infront of the weapons,particularly if someone is fiddling about in the cockpit.

Cheers

Steve

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Remember it wasn't so much the cooling of the guns which was the problem - much more icing. Flying thru' cloud at low level and then proceeding to higher altitude - uncovered gun muzzles first recieved a nice dose of moisture from the cloud and then iced up at altitude, jamming the weapon operation. The coverings for forward facing weapons was more for that phenomenon than strictly the cooling effects.

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The sealing was primarily to prevent excessive cooling of the guns (especially at altitude) as the Brownings were an open breech type weapon. Rear facing guns wouldn't have the wind rushing through them so wouldn't need sealing. Not sure about front facing turret guns.

I would expect belly pack guns to need sealing, but it would depend on their type and the spent cartridge collection system. If there was no external ejection of cartridges then there wouldn't be any holes for the wind to flow through and sealing would be less necessary.

DP

If we're talking about 0.30" or 0.303" Brownings (or even 0.50" Brownings), then I'm certain that they are fired from a closed breech. The Browning's breech is fully closed when the trigger is pulled and the firing pin strikes the primer on the cartridge.

An open breech weapon is something like a Sten gun, where the trigger pull releases the breech block to spring forward, pick up a round from the mag, and it fires as the breech slams closed and recycles the weapon's working parts for the next shot.

(Years of Cdn Army training coming in handy for this answer!)

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If we're talking about 0.30" or 0.303" Brownings (or even 0.50" Brownings), then I'm certain that they are fired from a closed breech. The Browning's breech is fully closed when the trigger is pulled and the firing pin strikes the primer on the cartridge.

An open breech weapon is something like a Sten gun, where the trigger pull releases the breech block to spring forward, pick up a round from the mag, and it fires as the breech slams closed and recycles the weapon's working parts for the next shot.

(Years of Cdn Army training coming in handy for this answer!)

The Browning .303 was definitely an open breech weapon. Main reason for this redesign was to avoid the risk of rounds 'cooking off' if they were sealed into the breech of a gun that had just fired a sustained burst. The reason for the tape was to prevent damp air (i.e. 'cloud') getting into the barrel and then freezing as the a/c climbed to altitude, but the idea of the red tape warning that the guns had been loaded was valid. There was a story that you could identify an RAF armourer by the dreadful state of his hat; rather than use the specially designed wire cocking tools, the crafty armourer would whip off his hat (the fore-and-aft type) flip it over the cocking handle and give it a yank. Job done, and it saved a few minutes.

If you want to see condoms in action, take a look at some of the colour photos of Mosquitos in Malta. They're not 'corks stuffed into the barrels', they're rubbers over the tops of the eliminators.

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Great responses guys - thank you.

The question remains though, condoms or no condoms for my BoB Blenheim (I hope the concensus is 'yes', as it's going to be on my club's stand at SMW!).

Cheers

Cliff

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There was a story that you could identify an RAF armourer by the dreadful state of his hat; rather than use the specially designed wire cocking tools, the crafty armourer would whip off his hat (the fore-and-aft type) flip it over the cocking handle and give it a yank. Job done, and it saved a few minutes.

Fred Roberts ("Grumpy" Unwin's armourer, for a time,) in "Duxford to Karachi," mentions this, and says, "Despite the claims of lots of people that we used our Field Service caps to cock the Browning guns, I never heard of this or saw it happen. We would have had to buy a new cap if we'd damaged it in any way. We all had a cocking toggle that we made with a piece of thick fence wire and a 3" piece of broom handle. This we were never without when on duty."

The fabric patches were a fairly late entry into the Battle of Britain; Supermarine list them from 24-9-40, with a note that "covers" were used in the gun tunnels before then. I haven't been able to find out what they were, but early tunnels appear to have a slight "step" inside, which might have been for those covers. Certainly, if you look at early BoB photos, the patches are largely conspicuous by their absence. It's entirely possible that Blenheims used the same system, at first, so, as with the Spitfire l/e, all you'd see would be the holes.

Edgar

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The Browning .303 was definitely an open breech weapon. Main reason for this redesign was to avoid the risk of rounds 'cooking off' if they were sealed into the breech of a gun that had just fired a sustained burst.

Not sure where you're getting your info from, but a Google search confirmed what I know from first-hand experience with Browning .30 cal MGs

http://en.wikipedia.org/wiki/M1919_Browning_machine_gun

The wiki entry talks about the various uses and calibres used in this weapon (including .303 for aircraft), but it describes its operation as firing from a closed breech.

Was the system used in British aircraft set up to hold the breech open somehow between bursts? I wasn't able to find anything that described that happening, or alluded to a redesign of the weapon to do so. I'd be interested to read more about that.

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The British .303 Browning was redesigned by Capt. E.S.R. Adams to hold the breech block open with an empty chamber to avoid cook-offs.

Google doesn't help me find more about this. I am guessing than rather than undertaking a re-design of the gun itself, that Capt Adams' work revolved around the Browning's cocking mechanism. I could see how its operation could be used to pull a round out of the belt on the back stroke, hold it there, and that the pilot's 'trigger pull' in the cockpit could release the bolt to fly forward, lock in position, and then fire the action. Clever stuff.

I watched a Browning cook-off in the 1970s on a firing range in Germany, but this happened while the breech was being hauled open at the end of a long burst; everything bad went straight down into the pile of spent brass and links under the gun. Lots of smoke and two startled soldiers. Exciting stuff, and fortunately nothing was damaged except for some underwear.

This is very interesting new info for me! If anybody has something they could link, post or send to me, I really would like to see how this works.

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The British .303 Browning was redesigned by Capt. E.S.R. Adams to hold the breech block open with an empty chamber to avoid cook-offs.

Ah ha, that would explain something that has puzzled me about the Browning - why British aircraft used the patches, but US didn't. If the breech open only applied to UK made guns then that would explain it.

DP

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Ah ha, that would explain something that has puzzled me about the Browning - why British aircraft used the patches, but US didn't. If the breech open only applied to UK made guns then that would explain it.

DP

I think that the American a/c designers paid a bit more attention to gun heating, so the problems of icing wouldn't have been a problem (if you see what I mean).

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I think that the American a/c designers paid a bit more attention to gun heating, so the problems of icing wouldn't have been a problem (if you see what I mean).

But some I think still used ducted warm air rather than that new fangled electricity. I'm thinking P-47 but don't shoot me if I'm wrong.

Steve

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Google doesn't help me find more about this. I am guessing than rather than undertaking a re-design of the gun itself, that Capt Adams' work revolved around the Browning's cocking mechanism. I could see how its operation could be used to pull a round out of the belt on the back stroke, hold it there, and that the pilot's 'trigger pull' in the cockpit could release the bolt to fly forward, lock in position, and then fire the action. Clever stuff.

I watched a Browning cook-off in the 1970s on a firing range in Germany, but this happened while the breech was being hauled open at the end of a long burst; everything bad went straight down into the pile of spent brass and links under the gun. Lots of smoke and two startled soldiers. Exciting stuff, and fortunately nothing was damaged except for some underwear.

This is very interesting new info for me! If anybody has something they could link, post or send to me, I really would like to see how this works.

Very happy to read nobody got injured.

All my info there came from good old R. Wallace Clarke's "British Aircraft Armament" Vol.II, if anybody knows more/better I'd be glad to hear about it myself.

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When we are by '303 Brownings... . Would somebody know why the Spitfire guns had to be cocked on the ground? Seems kind of dangerous idea to me, seeing all those possible bumps and accidents during the take off. The Germans flew with their MGs not cocked, and the procedure before fight was to release safety blokade and cock the guns. The idea lookes better to me when it comes to safety precoutions. I wonder, was it forced by construction of the gun or something else came by? And how it worked by american 0,5" Brownings?

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the guns had to be cocked on the ground because of the manner in which they work.

When you pull the charging handle (cocking handle) of the gun, it simply moves the first round into a position whereby the block and bolt can receive it. You need to pull the charging handle again to place a round in the breech, with the second round now placed in the feeder. Haven't done this in anger but have done a dry run on a .30.

Incidentally, the Browning is a closed bolt weapon - the firing pin is within the block and is released by the sear. I'm led to believe that the RAF modification to the gun allowed a second sear to hold the block open afte firing stopped. This was to remove the risk of a round cooking off in the breech. The second sear was released as the firing button was pressed, allowing the block to move forward and chamber a round.

Think this is correct but without seeing the real thing I'm only putting 2+2 to make .303.

Bob

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