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ImpStarDuece
06-11-2008, 10:28 PM
Quick question: Did the Browning Machine Gun, Cal. .50 used on USAAF fighters during the war use the 36" or 45" barrel as standard?

Or did it vary from fighter to fighter?

ImpStarDuece
06-11-2008, 10:28 PM
Quick question: Did the Browning Machine Gun, Cal. .50 used on USAAF fighters during the war use the 36" or 45" barrel as standard?

Or did it vary from fighter to fighter?

PanzerAce
06-12-2008, 02:15 PM
AFAIK, the M2 never came with a 36" barrel, so they would have used the 45"

One13
06-12-2008, 03:06 PM
I believe all aircraft guns used a 36" barrel, they were all fitted with a perforated metal shroud.
Guns used on the ground used the 45" barrel without the shroud.

Kocur_
06-12-2008, 03:35 PM
According to Chinn (and this (http://www.liberatorcrew.com/15_Gunnery/01_50cal.htm))the aerial .50 M2 had 36'' barrel, which weighted merely 10 lbs (4,54 kg), compared to 27,4 lbs (12,43 kg), 45'' barrel of M2HB. Making the barrel as light as possible was crucial for rising the ROF of .50 M2 so I dont's see how possibly could any aerial M2s have any other barrels than 36''.

PanzerAce
06-13-2008, 02:55 AM
I stand corrected. Must be a REALLY thin barrel relative to the HB models if they cut 17lbs off of it. Probably since they don't have to worry about them overheating, since you have airflow + VERY limited ammo reserves.

Also, Kocur, while on the M2 platform, cutting the weight of the barrel would be a way to increase the ROF, there are other ways, such as changing the spring rates. Example: people issued grease guns would often replace the main recoil spring with a cut spring out of an M2 to bump up the ROF.

Of course, when you start getting into piston and direct impingement op guns, other stuff comes into play, such as powder burn rates, gas tap size, etc. But that's a different issue altogether.

Kocur_
06-13-2008, 03:22 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PanzerAce:
I stand corrected. Must be a REALLY thin barrel relative to the HB models if they cut 17lbs off of it. Probably since they don't have to worry about them overheating, since you have airflow + VERY limited ammo reserves. </div></BLOCKQUOTE>

Oh they did worry about overheating. I can't remember the exact numbers of rounds it was permissable to fire in continous burst (the document mentioned P-47 IIRC) but I remember my impression that it was a low fiure.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PanzerAce:
Also, Kocur, while on the M2 platform, cutting the weight of the barrel would be a way to increase the ROF, there are other ways, such as changing the spring rates. </div></BLOCKQUOTE>

True that, but the very first thing you want to do is to increace kinetic energy of the recoiling group to speed it up. In case of a recoil operated weapon the only mechanical way (that is apart from gasodynamic effects utilised by using a muzzle booster - Hiram Maxim was the first to use it, some of us may be familiar with MG3 having it too) to achieve this is to reduce weight of said recoling group, if other thing were kept equal. And to do that you can cut barrel as much as possible and cut bolt (http://www.liberatorcrew.com/15_Gunnery/02_30cal.htm).

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PanzerAce:
Of course, when you start getting into piston and direct impingement op guns, other stuff comes into play, such as powder burn rates, gas tap size, etc. But that's a different issue altogether. </div></BLOCKQUOTE>

It sure is, yet the key thing is the same and it is speeding up recoiling group by giving it extra energy.

One13
06-13-2008, 11:46 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kocur_:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PanzerAce:
I stand corrected. Must be a REALLY thin barrel relative to the HB models if they cut 17lbs off of it. Probably since they don't have to worry about them overheating, since you have airflow + VERY limited ammo reserves. </div></BLOCKQUOTE>

Oh they did worry about overheating. I can't remember the exact numbers of rounds it was permissable to fire in continous burst (the document mentioned P-47 IIRC) but I remember my impression that it was a low fiure.
</div></BLOCKQUOTE>

From cold pilots and gunners were instructed to fire first a maximum burst of 75 rounds without damage. After that they could only use 25 round bursts.
This problem was solved in January 1944 when stellite-lined and chromium-plated barrels were introduced.