mikemike
Posts: 489
Joined: 6/3/2004 From: a maze of twisty little passages, all different Status: offline
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quote:
ORIGINAL: FatR Didn't know about the rimless cartridge. Can you propose any alternative solution? Right now I can think only of adopting some of the Army's twin rifle-caliber MG design as universal. I found a remark in a book by I.V.Hogg about the development of the Machine Gun. He says that the IJA introduced the 7.7mm cartridge in 1932 in three different versions: rimmed, semi-rimmed, and unrimmed. Now I don't know if all these versions were actually produced in parallel, this would have been another home-made logistical nightmare, considering that the IJA never managed to phase out the 6.5mm weapons. Infantry MGs seem to have used rimmed cartridges, at any rate. So I see two ways of determining the rifle-calibre MG problem: either assume that there was already a rimless 7.7 cartridge in production and go with a rechambered MG15 copy (disregarding the propensity of Japanese arms engineers to botch such conversions - when they tried to improve on their pre-war Hotchkiss infantry MG they wound up with the Taisho 11 that needed oiled cartridges) or avoid that kind of headache, go with a straight copy of the MG15 and start manufacturing the 7.92X57 cartridge for the Air arm only. Here are the rifle-caliber MGs actually used by Japan:
Notice that the Army and the Navy used different 7.7mm cartridges; if I interpret the table correctly, the Army had semi-rimmed ammo, and the Navy rimmed cartridges. quote:
The problem is, Type 3 is, supposedly, a rechambered Browning design as well. So, I'm not sure if your table is correct. Note, though, that at least most HMG-armed Zeros envisioned so far carry all armament in the wings. Ho-103 instead of Ho-5 needed to be synchronized too and had the same problem. You're correct, the Ho-103, Ho-5, and the Navy Type 3 were all Browning derivatives, and lost about a third of their ROF by synchronization. Personally I think the best bet for HMG would have been to push the Navy Type 2, the MG131 copy, as it offered slightly better performance than the Ho-103 and didn't suffer nearly as much as the Brownings from synchronization, an important consideration for the Ki-43, at least. There was a reason why the Ki-43 wasn't switched to a twin Ho-103 armament. Otherwise, don't let anything fire through the propeller. That also goes for the Oerlikon-derived cannon of the Navy. I think it would have been impossible to synchronize them at all, due to their working principle. When the Fw 190 was armed with the MG FF/M, the cannon were mounted in the outer wing positions exclusively for just that reason.
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< Message edited by mikemike -- 3/31/2010 5:10:59 PM >
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