Fastest grinding of ranged weapons to max skill in current version?

What the title says. What’s the fastest way for each ranged weapon skill?

If I’m not mistaken, you get the most xp for successful hits, so your best bet is lots of weak attacks against an enemy that you can’t hurt but won’t chase you. Your marksmanship goes up from shooting things at long range, so the only way to max that out is with something that can reach 60 tiles. Perhaps a Barrett and a few belts of .50 cal?

Your best bet is probably a pneumatic assault rifle and a turret that ran out of ammo. But that only handles rifles.
Launchers you might get away with a flamethrower against something immune to fire damage.
Pistols is hard, maybe the bullet crossbow? Or a V9?
Shotguns is pretty hard.
SMGs is also pretty hard, nothing springs to mind.

Shoggoths have insane health regeneration, so if you can somehow trap one you’re all set.

And of course, keep your morale up with good food, music, books, and maybe a lil bit of alcohol.