To be as close a clone as possible you would spray the gun assembled, masking off the gate-lock interface of the gas block to the muzzle device. Also, I've seen examples where the trigger was removed along with the pins, where the trigger and pins were coated and where the trigger was masked off but the pins were sprayed. These seemed to change over time. Also, the URX 3.1 for the SR-25 has gone through several variations; where all the K1s I've seen had the older, longer "gooseneck" then the current URX 3.1s.
The K1s were mainly upper kits for M110s so you can see many pics of Marines with them on top of older Gunkote'd M110 lowers (how the M110 were originally coated before the switch to Cerakote FDE).
Also, of the K1 uppers I've seen, they all had either a number stenciled on the bottom of the rear take-down pin lug or on the sidewall of the upper - like the Delta guns.