"Will he do anything more to you ?" "I expect he'll bust me," said Sergeant Mock.
To "bust" is the same as to "break." It means to reduce a non-com to the ranks.
"Are you going to stand it ?" demanded the stranger.
"Fat chance I'll have to beat the captain's game!" declared Mock angrily.
"But are you going to pay him back ?" "How ?" "Listen.

I was in the Army once, and I don't like these officer boys.

Maybe I've something against your captain, too.

Anyway, keep mum and take good advice, and I'll help you to make him wish he'd never been born." "Not a chance!" dissented Sergeant Mock promptly.

"Captain Holmes isn't afraid of anything, and besides he was born lucky.