This mod?

It's 'ReadMe.txt' says:

Compound Bow By TheReEvolutions Replace "w_ar_musket_hi.ydr" , "w_ar_musket.ydr" and "w_ar_musket+hi.ytd" with the files provided. you can just drag and drop by the way. -Location- ------------------------------------------------------------------------ update\x64\dlcpacks\patchday3ng\dlc.rpf\x64\models\cdimages\weapons.rpf update\x64\dlcpacks\patchday2ng\dlc.rpf\x64\models\cdimages\weapons.rpf update\x64\dlcpacks\patchday8ng\dlc.rpf\x64\models\cdimages\weapons.rpf x64w.rpf\dlcpacks\spupgrade\dlc.rpf\x64\models\cdimages\weapons.rpf ------------------------------------------------------------------------

so if you followed those instructions when installing, you should now have the files & folder structures to go through & revert to vanilla

'Ctrl+F3' in OpenIV to search for things by name ('w_ar_musket_hi.ydr' etc).
If you're not sure if you installed to those exact locations above, search for the files by name & replace them with their vanilla counterparts one by one.