Okay, a little info here...
The 'C' in G36C stands for 'Compact', which means that it is the smallest G36 variant currently on the market.
The 'K' in G36K stands for 'Kurz' or 'Kommando', and is the carbine variant of the G36.
As such, 'K' handguards cannot be swapped with 'C' variants, nor the other way around.
Neither will the A-series handguards, or the 'E' and 'EK' handguards.
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