OOC:
The prone thing was a snap judgement; I figured that if you wanted to grapple someone on the ground you have to go down with him.
In hindsight, maybe I was wrong rulewise but we have to roll with it.
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surprise round: Luddite tackles/trip the soldier. It works, the soldier is prone.
1st round: Luddite disarm (success). Luddite fails a grapple (and goes prone over the soldier). The soldier draws a knife and stabs Luddite.
2nd round: Luddite gets up (1/2 act), makes a free 5 feet move to disengage and gives a clean shot to Kim. That leaves Luddite with a 1/2 action that couldn't be a move (because of the free 5 feet).
The soldier gets up (1/2) and gets his partner's weapon (1/2).
3rd round: That's where we're at. You can go pick up the rifle (1/2 for move + 1/2 for pickup weapon). Or you can run for cover (tents are barely 30 feet away, for example). Or you can close in with the soldier and attempt up to 2 disarm maneuver.
Once you've taken your turn it'll be the soldiers turn.
I can't say if my prone ruling hindered you badly, but for the moment there is only one guard standing and Luddite can act before the bad guy so overall the situation isn't too bad.
BTW: as a result of a disarm attempt, you can end up with the weapon in your hands if you so wish and if your hands were free. I only stated that the weapon was kicked away because you specifically requested this effect in your post.
It's the second time that a PC use disarm to kick the weapon away instead of wrestling it away from the target (the first was Ronin), so I'm wondering if you are aware of that rule? A lot of PC do things primarily because they look cinematic so I didn't comment on it at first, but perhaps I should have. *sigh* I have much to learn.