[Update]
The latest firmware for MetrocPCS LG Optimus F6 (LG MS500) is “MS50010i”
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LG Optimus F6 (LG MS500) for MetroPCS Firmware
Here is the LG Official Stock ROM / Firmware revision “MS50010e” for LG Optimus F6 (LG MS500,MetroPCS) smart phones.
LG Optimus F6 (LG MS500) owner who have bricked their phones may need to reflash this Stock ROM/Firmware to recover the devices.
Download LG Optimus F6 (LG MS500) Stock Rom / Firmware “MS50010e”
http://csmgdl.lgmobile.com/dn/downloader.dev?fileKey=FW698486573210987654321/MS50010e_03.kdz
How to recover/unbrick LG Optimus F6?
Here you can find the ALL-IN-ONE TOOLKIT to extract .kdz ROM to .BIN/FLS format.
or you can download LG_KDZ_FW-Update_OfflineFix.zip from xda forum here. The Tool can be used to flash .kdz format ROM.