My armies\soviet\sniper\sniper.abp looks like:
Code
model =
{
"..\\..\\..\\Common\\CompleteMotionTree.abp",
-- Weapons in Use
"..\\..\\weapons\\rifle_mosin_nagant_sniper\\rifle_mosin_nagant_sniper.abp",
"..\\..\\..\\german\\weapons\\smg_mp40\\smg_mp40",
-- Common Soviet Gear
"..\\..\\sovietcommongear.abp",
-- Main Mesh
"sniper",
}
Notice that mine is above the main mesh. You do not want it to be after the main mesh.
If yours still does not work, I would suggest using the Rebuild option in Mod Builder to make sure it is actually being updated.
Edit: If you are getting the blue box, that means your path is wrong, even if you think it is right. If you are getting an invisible weapon, then you are using the wrong animator in the entity_blueprint_ext or the wrong anim_table in the weapon.