//Put this .cfg in your CFG folder. (common\Black Mesa\bms\cfg)
//Load Black Mesa from your steam games list.
//Open up the console and type in bind "t" "exec invis_fix.cfg"
//Replace "t" with any keyboard key you want.
//When you get the invisible weapon bug ingame just press the "t" key to refresh your weapon model. 
//Done! :)

record stop
stop
echo [invisible weapon bug temporary fixed!]
//Fix made by By gtamike_TSGK
//[Bugs/Glitchs/Problems] Black Mesa retail version
//https://www.youtube.com/playlist?list=PLgSd4b0ED7lvbgGZjjktoCIqbPtXk69B7