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UberDemon
06-01-2006, 06:14 PM
Heavy Machine Gun (12.7-13mm/.50cal) info from Anthony Williams (Author)

From Anthony G. Williams' "Rapid Fire: The Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces": (Only models used in WW2 aircraft)

Country/Model/Operation/Feed/Rounds per Minute
================================================== ============
Germany/RhB MG 131/short recoil/belt/900
Italy/12.7mm Breda-SAFAT/short recoil/belt/700
Italy/12.7mm Scotti/gas&blowback/belt/700
Japan/Ho-103/short recoil/belt/900
Japan/13mm Type 2/short recoil/belt/900
Japan/13mm Type 3/short recoil/belt/800
USSR/UB Beresin/gas/belt/900-1050
USA/Browning M2/short recoil/belt or steel link/600-800

"While the Browning's projectiles lacked the destructive effect oc cannon shells, their fairly high velocity and combined rate of fire made a six-gun installation a formidable armament, with the added advantage over mixed-gun installations of a greater ease of aiming. [...] The USAAF, not concerned with shooting down bombers, were not at first particularly interested in adopting 20mm cannon..."

(Paraphrased) Notable exceptions were the P-38 (1x20mm), P-61 (4x) and B-29 (1x in the tail gun along 2x.50"s). USN was more interested in 20mm cannons, concluding that one 20mm = 3x.50" destructive power. AN-M2 (20mm) was used in some Corsair and Hellcats (nightfighters), but used mostly after the war and considered unreliable. Pilots prefered 6x.50"s for fighter vs fighter combat, and the destructive power of cannons was not necessary against the nimbler, non-armored Japanese fighters or bombers.

"The 12.7mm UB offered a better combination of weight and performance than the equivalent .50" Browning and was one of the best guns in its class."

"Another interesting contrast is provided between the weapons turned out by the British, Germans and Americans on one hand, and the Soviets and Japanese on the other. The Soviet and Japanese guns commonly had a higher performance (in terms of rate of fire) and a significantly lighter weight than equivalent Western weapons, a tradition that the Russians have continued to this day. The Soviet 12.7mm Beresin, 20mm ShVAK and 20mm B-20, and the Japanese 12.7mm Ho-103 and 20mm Ho-5 are good examples."

"How could they achieve this? It seems likely that they took a much more pragmatic attitude to weapon life than the Western nations. For example, the 20mm Hispano was initially designed for a life of 10,000 rounds. On investigation during the war, it was discovered that very few guns managed 1,000 rounds before being destroyed in action or in a crash, and the majority never fired more than a few hundred rounds. In fact, the Hispano was later lightened but could still achieve 2,500 rounds even for the smaller components, with the main elements lasting for 5,000 rounds. A designed gun life of 500-1,000 rounds might well have permitted a much lighter construction and/or a higher rate of fire without any practical disadvantages."

Please note that these comparisons do not take into account capability of shooter, g-forces, gun barrel length, type of ammo and ammo configuration. They are addressed in the book, but would take forever to compile here (well, more time than I am willing to put into it... http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif )

carguy_
06-01-2006, 06:20 PM
Looks like people forget overheat issues too often http://forums.ubi.com/images/smilies/shady.gif

WTE_Galway
06-01-2006, 06:42 PM
Originally posted by carguy_:
Looks like people forget overheat issues too often http://forums.ubi.com/images/smilies/shady.gif

overheats, freezing, other mechanical jams and misfires are not really modelled .. probably fortunate as the gun-jam-whiners would be unbearable

UberDemon
06-01-2006, 07:06 PM
Originally posted by carguy_:
Looks like people forget overheat issues too often http://forums.ubi.com/images/smilies/shady.gif

Regarding the book, it is just short of 300 pages long... but it is hard to compile all relevant info from that. The information on aerial guns is 60 pages long, plus there are several appendices. A great book. I have exchanged some posts with the author before when I was moderator for Butch2K's All About Warfare forum years ago.

Most of the issues including durability, nose vs wing guns (and associated decrease in rpm due to synchronization vs concentrated firepower), as well as weight of guns and ammunition are all discussed.

Waldo.Pepper
06-02-2006, 01:03 AM
The same conclusions, in a very concise manner, are made in the book World War Two Fighter Combat by Alfred Price.

UberDemon
06-02-2006, 08:58 AM
I have a few books by Dr. Alfred Price as well. Generally very informative and rich on informative and comparison tables. "The Luftwaffe Data Book" contains a good synopsys of LW operations. Good stuff for history wanna-bees and geeks like me.