G36K is actually a G36C

[Lukas2438]

The assault rifle GB36s modelled and pictured in SWAT 4 (Elite Force) is a G36C (compact) used by police and swat forces.

The mislabeled K (kurz) variants are used by special forces of the Bundeswehr and other military, mainly for CQB.
Main differences are the barrel length and hand guard designs.
I tried to show the different spaces between the screws and barrel length in the picture below.

https://swat-4.fandom.com/wiki/G36C_Assault_Rifle

Here's another comparison between G36 variants; first one is C, second K: