As to the Bf109K-4 being rare, I can't say I agree.
My apology I used a shorthand literary style which misdirected you. I will expand to a fuller construct.
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As it is the K4 being non perked has no real competition from the
spit14 by being so rare in the same skys. ------------------------------------------------------------
The spit14 is rare in the K4 dominated skys. Due to the dogpile neon sign on the spit14, it's more bother than it's worth to burn off perks against mini hoards to play with it. So, we have never generated any real rivalrys between the K4 and spit14. To this I'm making the projection that the G10 would be a good foil to about 20K with its 20mm to the spit14 if it were unperked and more common. Any competent G14/K4 pilot would do quite well in a G10 chasing around a spit14 while being able to spray 20mm. From reading several sources the G10 looks like engine and WEP wise is a bridge between the G14 and K4 to about 20k. It was delivered with the DB 605DM, DB or DC like the K4.
Unless our G14's engine is changed with it's armament packages. The 20mm was mounted in the G14 standard low alt version's 605AM engine while the 30mm was mounted in the high altitiude G-14/U4 version's DB 605ASM. So do we have two G14 or a cluge?
Another possiblity. I keep reading that some K4 were delivered with 20mm motorkannon. How many in service flew with the 20mm?
There was this:
Prien and Rodeike 1995, p. 174.
Caldwell 1991, p. 292.
Armament of the K-4 consisted of a 30 mm (1.18 in) MK 108 engine-mounted cannon (Motorkanone) with 65 rounds, and two 13 mm (.51 in) MG 131s in the nose with 300 rpg
although some K-4s were fitted with the MG 151/20 as the Motorkanone. Additional Rüstsätze, or equipment kits, such as a 300 L (80 US gal) drop tank (R III), bombs up to the size of 500 kg/1,100 lb (R I), underwing 20 mm Mauser MG 151/20 cannon gondola pods (R IV) or 21 cm (8 in) Wfr.Gr. 21 rockets (as on the Gustav models) could be carried after minimal preparations; the latter two however were rarely used by Bf 109 units at this stage of the war,
but there is evidence that III./JG 26 were almost completely equipped with K-4s which were fitted with R IV. In addition there were problems with the 30 mm (1.18 in) MK 108 Motorkanone:The 30mm cannon were extremely potent weapons, but they had a tendency to jam, and apparently all of the K-4s supplied to III./JG 26 were also equipped with 20mm-guns in the hated underwing tubs. Uffz. Georg Genth's regular aircraft was a G-10, but on occasion he flew a K-4. He preferred the G-10 as a dogfighter, as the K-4's bulky armament sharply reduced its manouevrability.