Ki-27 7.7mm twin barrel "priming"

[islandee]

I have a translation of a description written by a Thai pilot about getting into his Ki-27 aircraft and readying it for takeoff: "[It] started immediately with a roar. I closed the seat cover after a weapons mechanic primed the 7.7mm twin barrels and placed it [them?] under my seat."

The guns certainly didn't go under the seat. What might he be talking about with regard to the seat, seat cover, and readying the 7.7mm guns? (Were the ammo belts possibly stored under the pilot's seat?)

Note: this is a translation from Thai where specialized technical terms may sometimes be misleading in translation. Hence, with apologies, I must note that the sentence in question (italicized) may turn out to be gibberish.

 

[Shinpachi]

"I closed the canopy after a mechanic loaded the twin 7.7mm guns and placed ammo under my seat."
Yes, they were placed under the seat.

 

[islandee]

Thank you!