MG 151/15, Cannon or HMG?

[Alex H.]

Well, that's pretty much the question. I have a book at home that states the normal armament of a Me109F2 as two Mg151/15 over the engine and one MG-FF firing through the engine. I know the Germans also used the MG 151/20 cannon on FW-190s and other planes.

If it isn't a cannon does anyone know why the Germans developed the Mg131 13mm weapon as well as the Mg151 15mm weapon? I wouldn't have thought there was enough difference to bother.

Alex.

[simon]

My understanding is that the definintion of a cannon was a weapon of 15mm in calibre or larger, any less than that and it's a machine gun.

The reason 15mm was chosen was because it was considered the smallest shell size into which you could practically fit an explosive charge.

I believe initially the Luftwaffe chose the Mg151/15 because of the shortcomings in the MG/FF during the Battle of Britain, however these were not widespread and were quite quickly replaced by the Mg151/20 (Better damage potential due to larger round and therefore exlposive charge).

The 13mm Mg131 was I believe a much lighter weapon with a much higher rate of fire than the Mg151/15, so much more suited to fighter combat and better able to penetrate the armour protection increasingly appearing on aircraft. Plus of course the ammunition being largely non-explosive in nature made it easy to manufacture in quantity.

[simon]

Just a quick follow up...

I always thought the Bf109Fs were armed with twin 7.92mm Mgs under the cowling and either one MG-FF (F-1), Mg151/15 (F-2) or Mg151/20 (F-3) all firing through the propellor spinner. Anyone else care to shed any light?