Rules:
*You can teleport into and out of it at will
*It has a couple of plug sockets and can connect to internet from the region you teleported in from
*You can take objects and people with you
*As already stated, it is (3m)^3 (3m*3m*3m). The walls are plain plaster with a light in the middle of the ceiling. The pocket dimension is topologically toroidal, so if there weren’t walls and a ceiling/floor (which you can actually destroy) you would loop if you went more than 3m in any direction. Gravity, then, is artificial and can be altered to anywhere from 0 to 2g from a dial on the wall.
Edit: additional specifications
*You can only teleport out to where you teleported in from.
*Time proceeds at the same rate inside the pocket dimension
*There is an eject button for those inside to get out if something happens to you
I mean, I’m not just talking about the guns. Imagine you’re at the bank, and then an individual in full tactical gear materializes behind you. He has a substantial amount of ammo and disappears every time he reloads. Molotovs, grenades, hell, you could even fit a flamethrower. You could fit a massive bomb into that space if you wanted. And you could potentially completely escape the effects of the blast inside you pocket dimension.
I’m not so sure about the smuggling thing. You would still likely be found out, since you’d have clientele and would be traceable to them either via phone, online messaging, or in-person interactions. Sure, you are immediately known about in the terrorist cases but you could pretty easily hide out pursuit, potentially getting away with multiple attacks, and there’d be little-to-no indicators of what’s about to happen for the victims until you appeared.
Like, this is some shit straight out of The Boys.
Okay, but it still doesn’t take more than one good hit to take said guy down - even in a vanishing tank they would eventually figure out where to direct the airstrike. And the bank would have given him the exact same cash drawer with just an imaginary gun he claims is in his pocket.
Yes, you absolutely would still get on the radar after a while as a big smuggler. Or whacked by a rival in your chosen organised crime group or insurgency. A Western government couldn’t really charge you with smuggling unless they can prove you have magical powers, though, and they would have to try and catch you doing something else illegal instead. The one exception I can think of is if you figured out something you can be the end consumer of, as well, but I don’t know what that would be.
Edit: Although, bombing might be an idea. You could fit a couple week’s supplies and and a car bomb amount of explosives in there, no problem. I doubt it would be more lucrative or safer than smuggling, though.