6315KM, 6310KM, other Keymo compatible muzzle devices and Surefire suppressor mounts have smaller/thinner wrench flats than the A2. When the flat is very close to the hand guard, or when the alignment shims are of slightly larger OD than the barrel, an armorer's wrench often has a hard to getting its 3/4 wrench into what little space there is to gain purchase on the flats.
JMW (Joint Muzzle device Wrench) has a thin 3/4" side specifically designed to work with the thin flats of suppressor mounts.
Please do not use a screw driver to torque muzzle devices. Doing so will deform the ports, and cause damage to them.
Bring it to a competent gunsmith.
Use a JMW wrench, torque to 25 +/- 5 lbs.