Conversion of BUFR format into grib
Here is how I would do this. ECMWF's ECCODES has a tool called bufr_ls and you can use that to  write the contents of that output to a text file. Then I would read that file into a scripting language such as Python and write out the contents as a GRIB file using PyGrib. You can also explore the output of bufr_dump and convert that also to GRIB if you wish. The full list of all BUFR format tools from ecCodes is given in this link BUFR tools
For more information regarding either of those softwares you can reach out to their support network and then get your doubts resolved. 

UPDATE

If you want a 100 % Pythonic solution then you can try  Python-Bufr which basically wraps ECMWF BUFR or use this python BUFR library - bufrpy