Hey there everyone,This is my take on the ejection of shells from a rifle.It's pretty easy to apply this to any other gun: shotgun, pistol. you name itAll you've got to do is change the first keyframe on the "Shell_Mover" object and you'll get cycled shell ejection.
Also, you've got to change the amount of particle emission, until it fits the cycle.And please ignore the first particle, because it clips into the side. The following particles are the ones you should use.It uses modifiers inside the F-Curve editor.
That's about it, I think.
I hope this helps!Cheers!UPDATE: Cleaned up material setups.