Tech Note

April 26, 1999

TECHNICAL NOTE 33, WHY IDENTIFYING AND SOLVING MALFUNCTIONS CAN TAKE SO LONG

ArmaLite’s Internet site often contains complaints that ArmaLite takes too long to answer questions concerning malfunctions.  Unfortunately, proper fault identification and correction can be a more complex task than it seems, and (as always) an answer takes longer to prepare than a question.

There are two types of malfunctions that produce interruption of the cycle of operations.  The first is the obvious blockage caused by a single obvious problem that is readily diagnosed and cured.  Lack of oil or dirt in the mechanism, or damaged ammunition are examples.  They are generally solvable with reference to the trouble-shooting guide of the operator’s manual.

The second is the obscure problem stemming from several sources or an obscure interaction of dimensions.  Failures to extract and eject commonly are of this type.  Self-loading rifles have fast-moving mechanisms, and the dynamics involved are more complex than they look, and are hard to observe or test in isolation.  The exact problem with a single rifle may be hard to diagnose, but application of several corrective measures such as chamber polishing, spring replacement, etc., may resolve the problem.

The fact is that we don’t know if the dimensions and tolerances of our rifles are absolutely optimal.  We do know that the rifles pass function tests before they ship.  We know that almost all work excellently in the field.  But we won’t really know that they’re optimized for years.   Over the years, occasional problems are categorized, malfunctioning guns are gathered and analyzed, and parts are changed.  The design is continually and slowly improved.

The M-16 rifle, for instance, has been Standard A in U.S. service since 1965, and its dimensions and tolerances are still being adjusted as problems are identified and cured.  Often, a problem is caused by an odd coincidence of dimensions.  One part may be at the small end of the tolerance, and another may be at the top end, causing an obscure problem that is corrected with changes to tolerances, not dimensions.

The amazing thing about our AR-10 is that they work so well given the small numbers that have been built.  We seldom learn of systematic complaints.  Few rifles arrive for diagnosis.  It takes a while to even learn that a general problem exists, let alone fix it.  Since introduction the changes to the parts have been few: introduction of the firing pin retarding spring, shifts in extractor dimensions, reduction of firing pin hole diameter.  With the design as generally satisfactory as it is, we will continue to have a hard time identifying and defining improvements, but we will continue to try.

Copyright © 1999 ArmaLite, Inc.