So I am trying to create a military shooter and therefore must have guns. I would like to include some weapons from real life (Ak-47, M16, Glock, etc.) and I would like to know what legal issues I might run into by using these names. Mainly if I could be violating copyright laws.
Copyrights don't apply to the names used. You mean trademarks. You copyright your game and you trademark the name.
Basically, it wouldn't be wise to use trademarked names in your game. Even though it's unlikely you would be sued and even if you were, you could possibly fight it under Fair Use, but do you want to take the chance?
If some gun company decided they didn't like how you used their name, even if they have little to no grounds for a case, they can STILL sue. Anybody can sue for pretty much any reason where there is doubt. If they have enough money to throw around, they can drag you through the mud, ruin your business and then just lift their lawsuit. They don't need to win in court, just destroy you.
Keep in mind that even if you don't use the name, if the gun in your game is an accurate replica of the real thing, it could still be a trademark issue.
EDIT: Something you could consider though is asking permission. You never know. They may simply not care. You might even try propositioning them to pay YOU to have their gun showcased in your game. It's not entirely uncommon for companies to be willing to pay for a bit of endorsement advertising.
Glock isn't a gun; it's a company. You would need permission to use any guns that they own the trademarks for.
I think colt owns the trademark for the M16. But "M4" was ruled to be a generic term, so you could use an M4 instead.
The AK-47 is a Russian gun and Mikhail Kalashnikov is dead.
As far as I can tell, you could still use the design of these guns, but you would have to call it something else. I think this is what Arma did
There's a good chance you won't get sued, but if you want to avoid issues altogether, you could make your own weapons. Just keep in mind how a gun works when designing them. If you want it to look like a military weapon, just make sure that it accepts a STANAG magazine. Look at other weapons for inspiration.
Since this is for a game, I would would personally create a fictional gun manufacture in your game. Like "Kirk MacQuarrie Arms".
Another thing to remember is that nobody owns copyrights on the concept of guns in general. If you use an existing model and change a few things, you should be safe.
Someone in this forum thread said:
If you are a big company, yes. If you have no money they won’t hunt you for using their gun designs. Would be a waste of resources to sue an indie without anything in his pockets.
You may also want to check out this reddit page.
It may happen that the manufacturer may ask you for attribution as appears to have happened in Battlefield 4 (Serbu Shorty et al.) where the manufacturer is now recognised in the descriptions, even though internally a nickname is used (for scripting and the like).