u/SteveTheHappyWhale (sorry for the summon, I think this one is important).
Op's projectiles seem to be returning to pool too early. They aren't hitting anything (invis mesh, blocking volume etc) and where they play impact fx changes dramatically along the flight path. Almost as if a blocking collision channel is moving back and forth. Thus why I think its related to obj pool lifespan.
Anyway here's a clip showing the impact plumes. Includes both M24 and Beryl.