First off, I'd like to give a big thanks to aerosoul94 for showing me where the ammo calculation function was in the default_mp. Without him, this wouldn't be possible. He told me to release this, so here it is: Unlimited ammo for version 1.14.
This is ONLY for custom firmware PS3s. It CAN NOT be transferred and used on an OFW PS3. It affects all players in the lobby, and yes, it works for every single weapon. It will not work unless you are host.
How to Use:
1. Download the file for your region and CFW version (I have linked to a folder containing all regions with an EBOOT for both 3.55 CFW and 4.21+ CFW).
2. Rename the downloaded file to "EBOOT.BIN".
3. Using an FTP program or File Manager, copy the EBOOT.BIN into the following directory on your PS3:
/dev_hdd0/game/YOUR REGION HERE/USRDIR
My Files (All regions and versions for 3.55 and 4.21+ CFW are included)
Here's a little video of it in action: