LOL! Yup, can think of 1,000 reasons to carry a knife...none of them have anything to do with shitting your pants. Although I'm pretty sure if you need to defend yourself using deadly force, shitting your pants is a given.
Lots of problems. Even if the can is rated for 300blk subs a supersonic round might blow it up. If'in I were you I'd be very careful or look into a 30 cal can.
Edit: Just noticed you have a 30 cal can so NM.