As a mostly pve player I dont have either, but they seem like a really solid combo since both weapons are top tier. I could see there being some situational/range challenges using that build though. I'm guessing the key is leading opponents into the right situation so your weapons are at their optimal range. With both SMG's and grenade launchers I like corner peeking at people and getting a few shots in, then try and get them to rush you. As they do, try crouching (or jumping in the right scenario) and backing up to somewhere they wont expect at a range you choose, then unload on them once they come around the corner. Rushing with an smg in this scenario has worked well for me in the past, and I am by no means a great pvp player. Again, feel free to take all this with a grain of salt since I dont play PvP that much, but if it works for my scrubby self, then it just might work even better for you!