An anti tank rifle for dealing with Cog armour at long ranges.
It would do more damage than the sniper rifle, but would also have a slower rate of fire and a longer reload time.
Link to the wikepedia article:
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://en.wikipedia.org/wiki/Boys_anti-tank_rifle&ved=2ahUKEwizrMe6z5qUAxXoQEEAHbUBDfYQFnoECB4QAQ&usg=AOvVaw3rfWKRw3xaRL0K0858TdTa
Image from the article: