if you have a problem with runners, and don't mind giving up a suit slot, belt slot, pocket or webbing (you decide what's more important) I HIGHLY recommend getting a M4A3 pistol (custom if you can), slapping a red dot and laser on it and loading it with hollowpoint from the special ammo vendors in prep. It has no AP at all but each bullet does 60 damage to xeno castes without armor, and you get 8 shots you can basically fire as fast as you can click. in my experience you'll crit a runner in 3-4 hits, and scare it off in 2. Very handy if you have the space for it, also recommend taking a throwing knife in your mouth slot because that does 100 damage before armor and is reuseable. basically a free backup if you run out of ammo or a good way to guarantee a cheeky hit if you're running away from a xeno since throws are guaranteed to hit the tile you're aiming at (assuming its in range, throwing knives can go to screen edge though). Just don't hit friendlies, you'll break their bones in 2 hits from full health and kill them in 3.