It always amazes me that when people think they need a backup gun or sidearm on a training course it means packing as much ammo for the 9mm handgun as it does for the M4 Carbine.   All it takes is a short training day to find out that a big chunk of the gear you brought with you was un-necessary.   An M4 Carbine is already probable the lightest and most handy firearms you can carry with you during the day and with a gun good sling you should be able to let go of the gun and still retain the weapon.   I have several LWRCI M6A2 guns and I tend to shoot the 77gr MK262 bullets.   These bullets weight a little more than the standard M193 ammo, but in my opinion it’s a better up front round.

When I carry a back up gun and I’m already carry a an M4 Carbine,  I am back to the old dog, my Colt 1911.   The Colt 1911 with 2 spare Wilson Combat magazines is all I need to retreat from a position or hold off a threat until I get my LWCR M6A2 back up and running.   I have yet to have something like that occur, but I have trained for it.   I am very confident that 24rds of 45acp is plenty of back up ammo and if the fight needs more than that,  I’ll more confident just turning around and running the other way.   A couple grenades my help boost my confidence though.