For unlimited bullets and life:

Copy MADDOG2.EXE to C:\
Hex edit the file.

Search for 26 FF 8F B8 34    Change all 6 occurances
Change to: 90 90 90 90 90

Search for FF 8F BC 34
Change to: 90 90 90 90

To start game: change to CD-ROM drive, but type   C:\MADDOG2.EXE
to start the game.