Translation of "caliber" into Japanese

Oh, hey, how did you know my gun's caliber?

なあ どう や っ て 銃 の 口径 が わか っ た ?

Hokkai 's teacher , Asaka also saw his caliber , and trusted him deeply .

また 師 明霞 も 北海 の 器 を 見抜 き 、 信任 が 篤 かっ た 。