This pistol either has a 100% crit rate, or 0% (it crits when the target has no cover). When it crits, it has a much higher multiplier than normal: any integer from 2 to 5 times the damage.
Using this weapon is good when you have Dietrich in your party, because his Nerve Bolt can flush enemies out of cover, which allows you to crit them. You should have another weapon for when everyone is behind cover.