Armature Bone Overrotates

Hey all, new here and first post. Trying out unity (previously a DBP user), and been trying to figure out this small issue I'm having. I have a model of a human, modelled in blender. Now some/most of the animations currently work fine. But, I notice that one of them has an issue with what appears to be a single bone. This seems to only be occurring on this one animation block, not on all of them, ie: when it rotates along the x axis (in blender). It rotates about an extra 30 degrees less and/or further. It is odd that only one of these seems to do it.

I've had this occur with another model I made, where every bone works but the leg... which just stays still...

Now, I guess it pertains to the blender side of things than unity, however I have been looking through the forums and tried many things.

A second quick question I had, was with respect to proper way to model an object for unity. Should weapons, be modelled at 0,0,0 origin and contain no location keyframes (just rotation) or modelled in the users hand (as a separate object obviously) then put into unity?

Thanks