http://pastebin.com/7VRmjaDC

I loaded it with ender magazines, and it crashed my server as soon as it fired.

Thanks for the report, this is a duplicate of #197

Okay, well I THOUGHT it was a duplicate, but I dug into the stack trace and it seems it's a little bit different. Yours looks like a missing method error, which is very weird. I will treat this as a different issue until I can see what's really going on with it. It MIGHT be the same issue as #197

You have "@SideOnly(Side.CLIENT)" on EntityShotBase's setVelocity override (which is being accessed at the end of seekTarget). I'm somewhat surprised that this only causes problems for Cauldron servers.

Well, setVelocity IS a sideOnly method [in vanilla], but that call shouldn't be occurring without an isRemote method check. Thanks for the heads up.