VidMuze’s Mike Gentilini jr. offers up a freebee download of what he calls his Gun Shell Ejection Kit which includes for a .45 Cal Pistol Shell, .223 Rifle Shell, and a 12 Gauge Shotgun Shell. He also has a quick video showing how to add shell ejections from gun props using the ejection kit in After Effects.

…I’ve just finished creating 3 different 3d gun shells that rotate in a 360 degree loop, simulating a shell ejecting from a gun. This kit is completely free and anyone can download it and use it wherever they like. All 3 of these effects are pre-keyed which makes them “plug and play.”…

The Gun Shell Ejection Kit consists of pre-rendered shells video clips that rotate 360 degrees. By using time remapping and some keyframes in After Effects, Mike shows how to add convincing muzzle flashes as well as smoke charges from the barrel of the gun and a shell ejection using the freely downloaded shell kit.

The renders are pretty basic and straight forward, which is all that is needed for something that shows up on screen for a few frames, moving, and at a scaled size.