This achievement requires you to get one hit marker (x) with each weapon type in the game.
Things to note:
MG42, Browning LMG don't count towards hits.
Pistols as far as I'm aware do NOT count as a Semi-auto weapon. Must be done with one of the Semi-auto rifles.
You can hit the same enemy with different guns.
This achievement is very RNG based as gun spawn locations change every new match.
The gun I'd get out of the way first would be the bolt-action manual rifle as it can be a pain in the ass to hit someone. Another way to get an easy kill with this is to down an enemy player then shoot them while they are crawling.
Don't forget to check dead enemies bodies as they may be carrying a gun you need.
Defiantly possible solo. But done better with a squad. In squads you can have team mates loot for the guns you need and keep hold of them for you until you need a hit with the next gun. For example if you find a shotgun and SMG, get your team member to find a semi-auto and Assault rifle etc. Then when you get your hits, swap weapons
Assault rifles are by far the most difficult to come across. These can be found in small numbers around the map. Mexico map (Desert) is by far the best map for these assault rifles as of the last update they added M1A1s and AKMs to the battlefield.
Etza on the Mexico map is a great place to find a chunk of these weapons. I'd only head there if your close. A tactical fridge has a chance of spawning on one of the larger pyramids in Etza. Tactical fridges usually have assault rifles inside them.
On the Normandy map (snow) I found assault rifles spawned more commonly in bunkers in certain locations around the map.
Steyer AUG A1 (Tactical/Orbital Fridge only)
Winchester Model 1912
M30 luftwaffle drilling
Browning auto 5
Sten Mk II
M1941 Johnson rifle
New guns (Not sure what these class as):