This is modem backup and update tool for Samsung Victory L300 [sprint Version]
Posting this with personal permission from XInterlopeRX from [OUDHS] group.
Just copy below zip in your SD card
Boot to your recovery (custom recovery)
Install this below zip from SD
It will do the rest.
It will take a backup of your modem, that too in Flashable zip file.
It will auto update modem to v. J8.
Keep your internal free, modem zip file should be around 60-80 MB
Also if you dont want V. J8 modem, you can flash back your backup zip from recovery.
http://www.oudhitsquad.com/android/Samsung/SPH-L300/efsbu7z-victory.zip