Damage 3d10+3 = I roll 2,5,8 - change 2 to 4, get 4,5,8 = 20 damage on normal setting. 22 damage and 3 pen on overcharge. A guardsmen with 12 wounds and TB3, with flak armour is on +6 critical after this shot.
...and that's not a death even in the head. To instagib the guardsman with an average roll you will need a normal sniper rifle with expender rounds and aim for the head. And PCs are usually tougher than a Guardsman...
Still a ridiculous amount in the crits which makes the rest of your session terrifying in combat. My rolled up guardsman started with 10 wounds, less then the example.
I maintain that the real problem is accurate, which needs a nerf like bracing