The 'F' is the Fumble range of the weapon. If you rolled below that number in an attack, you'll need to roll on the Fumble table (in Arms Law).
The 'B' is the breakage factor.
The Rel/Str is the Reliability/Strength of the weapon. The 'w' indicated that it has a wooden component (like the handle of a mace for example) and an 's' indicates it's a soft weapon, like a whip.
Anytime the operator of the machine/weapon rolls doubles of the numbers in the breakage factor's range (e.g., a breakage factor of 1-4 means that you'd check for breakage if you'd rolled 11, 22, 33 or 44), the device should check for breakage.
To check for breakage, roll d100 (open-ended) and add the device/weapon’s reliability. If the result is less than 100, the device breaks. Otherwise, it suffers a slight interruption in its normal operation.
A 'w' type of weapon should have its Strength lowered by 15 when hitting an “edged” object (e.g., one-handed edged weapons, etc.) and an 's' type of weapon has it's Strength lowered by 30 when hitting edged objects.
