Projectile.NewProjectile(vector1.X + vector2.X, vector1.Y + vector2.Y, speedX, speedY, type, damage, knockBack, player.whoAmI)
->
Projectile.NewProjectile(position.X + vector2.X, position.Y + vector2.Y, speedX, speedY, type, damage, knockBack, player.whoAmI)
Have a try~
And it seems that...