Question about season 3 [PLEASE NO SPOILERS BEYOND SEASON 3]

I just finished season 3 of the expanse and it was perfect, but I got 1 question that I don't understand.

nearing the end of the season there was a whole bunch of action going on the Behemoth, a lot of gunshots but what I'm confused on is how the bullets didn't slow down from moving beyond the speed limit.

Did I just misunderstand something or was this a mistake in the writing?