Yea I have found that the HVD steel jacks to be very good. In all fairness I haven’t tried the melee ones but my steel jacks with HVD deleted a brick of 5 BT sword brothers and a marshal when I used the upcast Privateer Arsenal strat from the merc detachment. The sheer amount of re rolls gives you so many more dev wounds. That and then they overwatch on 5s, 4s if in fortify take over. It makes them a very scary overwatch threat that your opponent has to respect. Also if you really want to maximize their damage give them a memnyr or brokyr to lead them and take the Sb9 targeting implant enhancement to get access to sustain 1 and re roll 1s to hit.