V8.0 / 8.1 (note that sound quality improves in gameplay):
You'll need SAAT (San Andreas Audio Toolkit) to replace these sounds (if you need a tutorial, I included a link to one in the README file). For this mod, you need to install this entire bank_137 first, because other sounds have been slightly shortened to compensate for higher quality gun sounds. This is how the rain bug can be fixed.
See the README for more details and instruction on how to install.
Extras:
V1.0 Suppressed gun sound pack (for those using additional suppressed weapons):
8.2 Release coming soon.