hook.Add("ShouldDrawLocalPlayer", "halogun", function(ply)
    if IsValid(ply:GetActiveWeapon()) and ply:GetActiveWeapon:GetClass()=="weaponclassname" then
        return true
    end
end)

hook.Add("CalcView", "halogun", function(ply,pos,ang,fov)
    if IsValid(ply:GetActiveWeapon()) and ply:GetActiveWeapon:GetClass()=="weaponclassname" then
        local view = {}
        view.origin = pos-( ang:Forward()*100 )
        view.angles = ang
        view.fov = fov

        return view
    end
end)