My request is for a gun that reads the owner's velocity and mass, and, when fired, creates a bullet with no sharpness, and the owner's mass and velocity, while reducing the owner's velocity to zero.

It'd be a gun for making emergency stops, and for re-usable jetpack rushes.

It will be more simple if velocity of the actor will just simple set to 0:0 through lua.

Actually, a Lua script that does that wouldn't move the actor at all.
Unless you specify it to, ofc.

What I meant was, actor works perfectly normally up until you fire.
Then:
BulletMass = ActorMass
BulletVelocity = ActorVelocity
ActorVelocity = 0

Wait, so when you're flying through the air, then you shoot, you stop dead, but the bullet continutes on said path?

I think that's what he means. I can't tell what would happen if you were facing backward though... would your velocity double? Or would you stop and have the bullet go right through you? Also, for that matter, what if you were standing still?

This is now more of a physics thought-challenge rather than a plausible Idea.

That it is. I think the script should calculate which has a higher velocity, the bullet or the actor, and then nullify the velocity of the faster slower object, while allowing the other to continue on it's path.

So, if you were flying through the air faster than a speeding bullet, the gunfire would halt you [no matter where you shoot it], but the gun would also serve as a sensible firearm when unmoving.

Read through that again a couple of times. Tell me if you spot the problem(s).

Also, as has been said, this would be much simpler with Lua.
actor.Vel = Vector(0,0);

Anyway, I'm pretty damn sure this topic is dead dead dead.

Uh... I meant slower. Really I did.

I don't see this as being dead while the idea is still plausible.

DEAD DEAD DEAD

Wait, wait...

Now you can let it die.