I have a big problem, i want that my weapons fall down like in reality. But the physic do some strange things..

Some of the AK's are fallen into the terrian, some fly 100 miles away when they hit the terrian and some stuck in the terrian.
What can i do to fix that?
Here is my code:
Code:
void waeponOnGround_main()
{
	wait(1); 
	c_setminmax(me);
	me.ambient = 100;
	me.pan = 10; me.tilt = -10; me.roll = 110;
	phent_settype(me,PH_RIGID,PH_BOX);
	phent_setmass(me,1,PH_BOX);
	phent_setfriction(me,100);
	phent_setelasticity(me,10,5);
	phent_setdamping(me,50,100);
	ph_setgravity(vector(0,0,-500));
	ph_setautodisable(0.05, 0.02, 10, 0.1);
	VECTOR vDrop;
   vDrop.x = 10; vDrop.y = 0; vDrop.z = 75;
   phent_addvelcentral(me,vDrop);
	me.material = mat_metal;
	//set(me,SHADOW);
	while(me != NULL)
	{
		if(vec_dist(my.x,player.x)>20)
		{
			if(player.skill8 == 0)
			{
				player.skill8 = 1;
				ent_remove(me);
			}
		}
		wait(1);
	}
}

Thanks, Ralph.