Well, if you set the bullets and the spaceship facing the same direction on their original sprites, i think you can then set the projectile angle to the player's angle every time you create one. If you are already doing that and the behavior is still weird like you are describing maybe you should upload part of your code, or even better a capx. so we can take a better look on what's going on.
Now, for the bullet to gain the same directional movement as the player. You could try and add some X and Y variables inside the bullet object and set them to zero, and then change them to specific values depending on the keys the player is pressing. And while they are on the screen you change their X and Y position values every tick. So for instance, the player is pressing to the right, the X would be 5 and the Y 0 so every tick the bullets fired would move to the right.... This might work weird depends how the ship moves, but I suggest you to start from there and improve it later.
Hope it helps o/