are you referring to the thorn bounty?
Either way, you can definitely get void guns, but if you want a void primary you'll need a drop. But personally I wouldn't worry about that. Vanguard quartermaster currently sells a void sniper (Amplified GEO-D6) for 150 Vanguard marks and the Crucible quartermaster is selling a void shotgun (Hard Luck Charm) for 150 Crucible marks. However you need to be rep 3 with either Vanguard or Crucible to get them.
But if you don't have the rep or the marks there's an even easier way to get void weapons. Just reroll any other HoW weapons you have with the gunsmith. Costs sfa, a few weapon parts and motes, and every reroll will have a random element. Ergo, you have a 1 in 3 chance of it being Void; and it won't take much effort or cost to get a void weapon with a decent enough roll.
If it is the thorn bounty and you aren't much chop in the crucible your best bet is to get a void shottie and a void rocket launcher and camp control points. I said earlier I wouldn't worry about a void primary because outside of the lighthouse or skolas the only void primaries are atheon's epilogue and word of crota, both of which are pretty crap and utterly uncompetitive with a lot of other primaries, unless you're a reasonable player. With the thorn bounty deaths count as they reduce your score, so not dying is more or less a score. Therefore I always recommend rock your favourite void specials and heavies, hopefully be a titan or warlock for the void subclass, and get points with those, and use your most effective primary as a way to win gunfights and stay alive, or at least put enough hurt on your opponent so that you can run away and get healthy again
