This work was one of those projects that took me A LOT longer to figure out than I thought. I initially was just trying to create a simple shell eject particle for my game, but I kept encountering some roadblocks regarding the rotation colliders for the particles not lying flat when hitting the ground. I later realized that Niagara particles do not inherit their collisions from the mesh and are ALWAYS spherical. Luckily some incredibly talented members of the community were able to show me some cool tricks to force the particle to lie flat once it collides with the ground, I would have never figured it out without their help and I have made a full video demonstrating and teaching you how to do it if you want to learn here:
https://www.youtube.com/watch?v=24ZdWCziDkg
And you can find the pack on my shop here:
https://www.artstation.com/marketplace/p/1Kgqb/bullet-casing-shell-ejection-niagara-particle?utm_source=artstation&utm_medium=referral&utm_campaign=homepage&utm_term=marketplace