A comprehensive article on ASL B#
etc was penned by Perry last century. I'm not sure if it was ever reprinted.
I presume it is still correct in all respects,
but I haven't looked in detail to see.
Synopsis: When Bad Things Happen to Good Weapons How Weapons Break in ASL, by Perry Cocke GEN30.5p51
ASL Weapons can disable (break permanently) on a DR >= than their X#, or they can malfunction on a DR >= than their B#. Some have a B# or X# on the counter. Those that have neither are treated as though having a B12 on the counter (these are said to have an inherent B12).
Some have a Low Ammo B# (D3.7)---a circled B#, aka a LA#---a LA# is
not a B#. ``All guns with a circled B# have an original B# of 12 (i.e., they malfunction on a 12).'' An Original DR >= the LA# and < 12 requires placement of a Low Ammo marker on the weapon [an Original 12, if it does not disable, is just a Malfunction: D3.71
WMH]. Once under a Low Ammo marker, a circle-B# Gun is treated as having an X# equal to its LA# and a B# one lower than that.
A weapon's LA# is never lowered. A weapon's B# or X# can be lowered for various reasons, and such lowerings are cumulative (see also A.11):
eASLRBv2.01:
A.11 PERMANENT BREAKDOWN: When a weapon uses a form of fire which increases its Breakdown frequency by decreasing the B#/X# (Sustained Fire, Inexpe- rienced Personnel [19.32], Ammunition Shortage, Intensive Fire, Captured Weapons, unqualified crews [21.13]), it also transforms the weapon’s Original B# to an X# during that use. Multiple causes of Breakdown frequency increase are cumulative.
EX: A German LMG with a malfunction rating of B12 uses Sustained Fire. During that attack it has a malfunction rating of B10 and X12. If its Original IFT DR is 10 or 11 the weapon malfunctions; if it is a 12 the weapon is permanently removed. If an American unit were using Sustained Fire with the captured LMG, it would have a B8/X12 rating.