I've looked on the wiki and all it says is "upgrade V5 weapons to V8 to get the trophy," well how the heck do I upgrade them? I'm about half-way through challenge mode and all my weapons are still V5, it doesnt show I can get more XP with them, so how do I get them to V6,7, and 8? Thanks for all responses in advance.
If you can afford the weapons, then always upgrade when you get the chance. Most will go quickly to V8. I think the holo-shield can be upgraded against one opponent, at least to V5. After that I think it starts fighting back.