gistfile1.txt

// also tried this slightly different way behaves different but the hard turn problem remains

    var mass = 1,
            maxSpeed = 1000,
            maxSteer = 200,
            distance = this.distanceTo(this.target),
            d = this.angleTo(this.target),
            steerX = Math.cos(d) * this.speed - this.vel.x,
            steerY = Math.sin(d) * this.speed - this.vel.y;

            steerX = Math.min(steerX, maxSteer);
            steerY = Math.min(steerY, maxSteer);

            this.vel.x = this.vel.x + steerX;
            this.vel.y = this.vel.y + steerY;

projectile.js

{
speed: 2000,
turningSpeed: .02,
angularDistance: function(a, b) {
    	var pi2 = Math.PI*2;
		var d = (b - a) % pi2;
		if (d > Math.PI) d -= pi2;
		if (d < -Math.PI) d += pi2;
		return d;
	},

update: function(){
var targetAngle = this.angleTo(this.target); // get angle in radians
    

    	var d = this.angularDistance(this.angle, this.targetAngle);

        if (d > 0) {
          d = Math.min(d, this.turningSpeed);
		} else {
          d = Math.max(d, -this.turningSpeed);
		}
        this.angle += d;

        var xf = Math.cos(this.angle)
        var yf = Math.sin(this.angle)

        this.vel.x = xf * this.speed;
        this.vel.y = yf * this.speed;

}
}