No K6 were ever built. The wing was ready but never mated to the K4 airframe. same for K8 etc.
No 109 ever mounted 2xMG151/15 over the engine. Too big.
The Mk103 was modified to fit inside the engine, but it wasnt used during the war for various reasons like excessive weight etc.
There is some suggestion that possibly a single K14 was issued to pilots but it crashed on the transfer flight.
This had the new DB605L and 4 bladed propeller.
It had the 3xMk108 30mm and 2xMG131 13mm.
The DB605L and 4 blade prop test machines provided a stunning increse in performance at high alts over the DB605D and 3 blade prop.
Anyway this K14 delivery stuff is just a rumor and IM NOT ASKING FOR IT IN AH!!!!!, OK? clear?

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Pongo most is common knowledge about K4 but ill dig up the specific references for the more obscure stuff.