Hey, Hellstotrmer1 here again. I took some time and cranked out UNSC M6D Handgun, UNSC M6C Magnum Handgun (M6A, M6B, M6E, M6F, M6K), and UNSC M7S Submachine Gun (SMG), added to HALO in Equipment D6. Also, I reworked UNSC M7/Caseless Submachine Gun (SMG), as it didn't feel quite like the SMG from the Halo games. It's rules get a bit cluttering (and if anyone has a simpler, better version, please leave this in comments, I would love to see it, and maybe even change out the rules for it!), so it was tweaked.
*Later that night, just before midnight*
Whoops, forgot to add this earlier...
UNSC M6J Carbine
This is another variant of the M6 series firearms, but instead of a handgun/pistol, it's been modified to be a carbine, closer to an assault rifle or SMG, but more than just a handgun.