Fighter Armament Question

[Crumpp]

We still use the M2 .50cal today.  Great weapon and it helped me get a little payback for Sept IIth while in Afghanistan.  We train our soldiers to fire 6-9 round burst's to maintain the M2's sustained Rate of Fire of 40-60 rpm.  
Firing it faster than that invites malfunctions although the M2 remarkably reliable.  To obtain a steady stream of fire on a target to suppress it we use three guns alternating bursts.
 
I notice on some gun camera footages some really long burst's of fire.  I'd like to know:
 
1.  How long were the pilots trained to depress the trigger on their M2LWAA?
 
2.  Did ALL the wing mounted armament fire at once or did the "banks" of M2's alternate to keep from stressing the individual guns.  Just like we do on the ground? If so how did this work? Seleniod? Interupter gear? etc..
Thanks!
Crumpp

[brady]

From What I understand Aircraft Weapons were expected to not last long, and were rutenialy maintained (including changing barels)after each sortie, so barel life was not a big concern.


 The following is from Anthony G. Williams and Dr. Emmanuel Gustin's excelent Book Flying Guns of WW2, I strongly recomend this book...

 ""750-850rpm unsynchronised-(for the 50cal M2)-.Right at the end of the war, a through revamp of the designe (with most parts being changed) produced the M3 vershion, with the rof increased to an impresive 1,200 rpm.......The reliabality of the M2 increased signistudmuffinantly during the war (with fixed guns being twice as reliable as Free guns). By the end of the war the stopage rate averaged around once in every 4,000 rounds."

[Crumpp]

Thanks taking the time to reply.
What I need to know was if say in a bank of 3 weapons on a P51D wing, did all three weapons fire at once or did One fire, then the next, then the next with the same going on in the other wing.  In other words when the pilot pulled the trigger on the stick were 6 MGs firing at once or were two guns firing at a time.  

IF all guns fired at once you got more lead flying at the tgt but increase your chances of a malfunction.  MG's just are not designed to fire continuously but in specified burst.
I think I've seen on the History Channel a film of P51's firing and I thought the guns where cycling thru the bank and not firing at once.

IF the guns cycle then you get a steady stream of lead without increasing the malfunction rate of the weapon.

Every MG has three rates of fire.

Cyclic which a theoritical ROF assuming the weapon has an unlimited supply of ammo, doesn't overheat, and never malfunctions.

Sustained ROF is the rate the weapon can shoot per minute and not overheat or malfunction over a sustained period of time.  A Vickers (water cooled) MG fired sustained ROF fired continously for 24 hours during the siege of Tobruk without a stoppage.

Rapid ROF is the Ohh Crap ROF.  It is designed for short periods and is the ROF you can shoot the weapon at for 2 minutes with a reasonable chance of no stoppages.

Sustained ROF for an M2HB is 40-60 rounds per minute depending on the weapon.  The cyclic in an M2HB can vary about 100 rds/min depending on how the weapon is set up.  It is listed as 450-550 rds/min.  This is much slower than the LWAA version.

Does anybody know for a fact if they cycle or not?

[brady]

I am queit certain they do not Cycle, that they all fire at once, what you may of sean is the tracers in the film giving the impreshion of interment firing from the different gun's.

[Crumpp]

No it was a film of the muzzles not the tracer going downrange.  Even then though its hard to tell.  

Do you know for a fact and if so what is your source?  Again, thanks for responding!!

[brady]

Wel I am asuming that they did not cycle between the guns (that they fired all at once), since I have never heard that they did(cycle), or read that they did, I can not recall ever reading of any refrence to this, other than the syncrosation that occure's for the firing of weapons through the Prop arc. I may be wrong but I would be suprised if I was on this point.

 Tony will wander in at some point and answer though I suspect and then we will both know for shure.

[Tony Williams]

(wander, wander...)

I know that some aircraft (especially German ones) permitted you to select which guns you wanted to fire, but I've never heard of USAF fighters selectively firing their batteries of .50 guns. AFAIK they all fired together.

What you have to remember is that a 300+mph headwind provides pretty good cooling...even so, pilots were advised to lock the bolts of their .50s open for a couple of minutes, following extended bursts of fire. About 30 seconds worth of continuous firing would ruin the barrel.

As far as other calibres are concerned, this is from 'Rapid Fire':

"Even so, restrictions on weapon firing have been applied.  For example, World War 2 US fighter pilots were told to fire 20mm bursts of no more than 20 rounds and preferably 10, with 37mm figures being 15 and 5 respectively."

Tony Williams: Military gun and ammunition website and discussion
forum

[Kweassa]

Woohoo!

 Tell that to the N1K2 sprayers

[HoHun]

Hi Crumpp,

>What I need to know was if say in a bank of 3 weapons on a P51D wing, did all three weapons fire at once or did One fire, then the next, then the next with the same going on in the other wing.  In other words when the pilot pulled the trigger on the stick were 6 MGs firing at once or were two guns firing at a time.  

They had all firing at the same time.

From the P-51D manual:

"The P-51D carries six free-firing 50 caliber machine guns, three in each wing. These guns are manually charged on the ground, and fire simultaneously when you press the trigger switch on the front of the control stick grip."

There's also a paragraph on jams in the manual - even a single gun jamming would have an impact on accuracy as the asymmetric recoil would yaw the aircraft's nose off target.

However, weight is a great concern in aviation, so it was unacceptable to triple the weight of the gun installation by carrying six guns to have just two firing simultaneously at any time.

>I think I've seen on the History Channel a film of P51's firing and I thought the guns where cycling thru the bank and not firing at once.

This could be an artifact of the filming process. The guns fire at around 12 Hz, while the typical cinematic frame rate is 24 Hz. That might give some strange interference effects! An observer on the shooting range would see nothing of it as it's just a cinematic illusion.

Regards,

Henning (HoHun)