I have tried the custom movement behavior on my projectiles to improve collision accuracy, but I'm facing 2 issues.
1. The projectile is not firing from player angle
2. Even with stepping mode set to 1 pixel per step my collisions are not detected
Capx link: copy.com/euCkQrnoHUPH
Two problems there. You need to set the angle after setting the speed. And you need to use the 'on step' trigger along with 'is overlapping' to check for collisions every step.
Here's an old example I made of a custom-movement bullet:
customMovementBullet.capx
And a ball bouncing between two 1px wide walls:
custom movement stepping.capx