You vs. the Spartan army.

You’ve always wanted to see Ancient Greece, right? Unfortunately a malfunction with your DeLorean sends you back July 6, 371 B.C. You hide it in a cave and go exploring. You find yourself on a field sandwiched between two great armies, the Spartans on on side and the Thebans on the other. You’ll have to get through the advancing Spartan lines to GTFO.

They’re advancing in phalanx formation and will carve you up if you try to politely elbow you aside. Fortunately for you I’ve received your temporal distress beacon and can help you out. The bad news is that as per usual I’m meddling with the Second World War, so I can only send you back the Allied weapons I can get my hands on. The Spartans lose this one, possibly because of you, so don’t worry about altering history.

Which one weapon do you want to maximise your chances of survival? These are the ones I can easily get my hands on, I’ll send it back fully loaded and with a stack of ammo as high as your head so you can take as much as you can carry:
If you want a handgun, I a M1911A1, a Browining High Power, a Smith and Wesson M&P or Enfield No2 revolvers.
If you want a sub-machine gun, I can send back the Sten Mk. II gun or the M1928 Thompson or M3 ‘Grease gun’.
If rifles are more your style, pick a Lee-Enfield .303, an M1 Garand a scoped Springfield 1903, an M1 Carbine. If you want a boomstick, Winchester 1897.
Want something a bit heavier, I can offer a B.A.R. or Bren gun.
If you want something a bit more…specialised, I can give you a stack of Mk II grenades, M1 Bazooka or the M2 Flame-thrower.

(Last one of these I promise).

Really? Promise?

The flamethrower, no question. That thing would scatter any army.

Yeah, grenades would be pretty effective as well if someone has never seen them before.

I think that anything on the list and about 15 seconds of ammo would be enough to have them running for the hills.

I picked the Thompson, because that is the only full auto I’d like to get my hands on.

But on second thought, I probably should have went with an '03, 1911, or M-1, because I own them and know exactly how they operate.

If not scatter them, it would at least be suited for drawing a nice “Do Not Cross” line on the ground. Get as far out of the way as possible and torch a small area between you and them, and they’ll probably get the message that’s it’s better to let you be a spectator.

I predict a Spartan skirmisher would nail me with a spear or a sling bullet or something, but if I had to try the flamethrower seems the best bet. Those things have far more range than you’d think, too.

The Thompson–aka the Chicago Typewriter.

TOP OF THE WORLD, MA!

65 ft effective range, apparently. The heaviest option by far though.

No.

A nice packed formation like that seems perfect for a barbeque. Plus “fire” seems like it would create a primal understanding and fear that might be lacking with a boom-stick.

Can I have an M-32 instead? Plus the stack of reloads? Frag and WP would be nice.

Then we’ll be talking!

If I’m limited to WW2 era weaponry, give me a bazooka and a couple hundred rockets.

The problem with a flamethrower is that 1) you are still vulnerable to ranged weapons, and B) it wouldn’t be new to soldiers who had experience with Greek Fire.

Dust off and nuke 'em from orbit
The only way to be sure

Barring that, for a heavy gun, if the Davey Crockett is out, then the mini gun from T2

Personal man portable firearm? Practicality says an M16-A2 with drum mags, but for sheer style, Thompson submachinegun with drum mags

The problem with a flamethrower or grenades is that I wouldn’t want a mass of soldiers to get that close to me. I’m not familiar with the area, so I don’t know how far away I could get. I’d want to be far enough away that I could fire from concealment. But if I was that far away, it might be smarter to hole up and not get involved. Handguns would have the same problem as the flamethrower or grenades. Still, fire is something the ancients would understand and want to avoid.

I have a couple of M-1 Carbines. Sweet little gun. Not much recoil, and pretty accurate. Not a lot of stopping power though. OTOH, they have a 15-rd. magazine and 30-rd. mags are available too. It would be good in closer quarters. Again, I’d rather not be that close.

I’ve never fired a Garand, and I haven’t gotten round to firing my SMLE, but one of those or the M1903 would be good for shooting from a distance. I have a couple of Mauser K-98s, which are similar. Helluva kick. The Garand carries eight rounds, the SMLE has ten, and the M1903 has five. ISTM that for ease of use and quickness of reloading, the Garand would be the rifle of choice.

The BAR or the BREN would be great for a fortified position, but I think they’d be too heavy and use too much ammo for a one-man show.

The Sten and the M3 were cheap. They worked, but when your life depends on quality…

Assuming I can’t get far away, I think I’d have to go for the Thompson. It’s heavy, but well-made. It has stopping power, and you can shoot single rounds. In a swarm attack, a short machine gun would be useful.

I think I’d probably go with the Thompson and wish I were somewhere else. Why can I never get a helicopter in these scenarios? (And yes, I know how to fly them. I could probably figure out how to start a military one.)

The main problem I have here isn’t that I can’t kill a Spartan warrior with a gun, because of course I can. It’s whether I can kill or scare away three hundred of them.

You simply cannot kill or disable three hundred men with any of the weapons presented in the scenario described, if the 300 are bent on killing you. You have no chance whatsoever of getting off 300 killing shots. My best chance of survival is killing some and frightening the others.

So I am torn between the flamethrower and BAR. I’d have to agree that the flamethrower would be a profoundly terrifying weapon, more so than a gun. To a person of that era a gun would be confusing, and they might not initially associate the loud banging noise with buddy a few ranks away falling down dead with a little hole in him. Today we are conditioned to fear guns, but at the time, death was up front and dealt in messy fashion. So some of them might get to me while I’m reloading - 300 men is a lot of men to shoot with ANY firearm.

A flamethrower would make you look like the God of war. They’d run for sure.

The advantage of the BAR, however, is that I can start killing them from hundreds of yards away, out of the range of any weapon carried by a human being at the time, and so IF I can convince them I’m killing them en masse, I can make them runaway before they are a threat to me. With the flame thrower I am certain they will run away if I can start incinerating them - but I am within range of a thrown spear. An M2 is good to 20-40 metres and a trained Spartan warrior can get me from that range, even if he has to take a run at me.

Isn’t it true that flamethrowers only carry enough fuel for a few seconds of spray?

7 seconds of burn time. That’s…not much - about 23 ms per Spartan.

Of the weapons on offer I’d take the BAR or Garand - ROF and penetration would be the prime reasons (the SMLE is a good rifle but slow to reload and a semi-auto would be better than a bolt).

Though if I could have my choice of WW2 infantry weapons it would be the MG42

With most of these choices given you’re already in the effective range of skirmishing troops, but even if you manage to avoid the dozens of rocks and javelins whizzing past your head, then you’re engaging in some anachronistic Tueller Drill… Except there’s thousands of them and they even have a mounted unit of horsemen (who may have been even trained by the legendary Xenophon himself!) attached to their army.

Unless you can portal in a Boeing B-29, I think you’re toast.

Not getting involved is the essence of my selection, if you’ll notice. As RickJay says, you’re not going to kill off either force (let alone both) with any of the offered weapons. Without fighting the OP’s hypothetical, the best I option I can think of is to put out a cross-cultural “Dangerous: Do Not Touch” sign without actually hurting anyone and pissing off their buddies. Ideally, they’ll avoid me, and I can slip away once they’re engaged with each other.

You don’t have to fry them all, just burn a hole in their lines.
If you can get an iPod with a recording by The Crazy World of Arthur Brown in their language and some speakers so much the better.