I borrowed this from another small but informative forum.
I had never considered this as a potential problem. Good food for thought.
> THE FOLLOWING TRAINING ADVISORY WAS FORWARDED FROM GWINETT COUNTY
POLICE DEPARTMENT – LAWRENCEVILLE, GA
> In September of this year a GCPD officer was involved in a situation
which quickly became a use of deadly force incident. When the officer
made the decision to use deadly force, the chambered round in his duty
pistol did not fire. Fortunately, the officer used good tactics,
remembered his training and cleared the malfunction, successfully
ending the encounter.
> The misfired round, which had a full firing pin strike, was collected
and was later sent to the manufacturer for analysis. Their analysis
showed the following: “…the cause of the misfire was determined to
be from the primer mix being knocked out of the primer when the round
was cycled through the firearm multiple times”. We also sent an
additional 2,000 rounds of the Winchester 9mm duty ammunition to the
manufacturer. All 2,000 rounds were successfully fired.
> In discussions with the officer, we discovered that since he has small
children at home, he unloads his duty weapon daily. His routine is to
eject the chambered round to store the weapon. Prior to returning to
duty he chambers the top round in his primary magazine, then takes the
previously ejected round and puts in back in the magazine. Those two
rounds were repeatedly cycled and had been since duty ammunition was
issued in February or March of 2011, resulting in as many as 100
chambering and extracting cycles. This caused an internal failure of
the primer, not discernible by external inspection.
> This advisory is to inform all sworn personnel that repeated cycling of
duty rounds is to be avoided. As a reminder, when loading the weapon,
load from the magazine and do not drop the round directly into the
chamber. If an officer’s only method of safe home storage is to
unload the weapon, the Firearms Training Unit suggests that you unload
an entire magazine and rotate those rounds. In addition, you should
also rotate through all 3 duty magazines, so that all 52 duty rounds
are cycled, not just a few rounds. A more practical method of home
storage is probably to use a trigger lock or a locked storage box.
> FURTHER GUIDANCE:
> The primer compound separation is a risk of repeatedly chambering the
same round. The more common issue is bullet setback, which increases
the chamber pressures often resulting in more negative effects.
> In addition to following the guidance provided above of constantly
rotating duty ammunition that is removed during the unloading/reloading
of the weapon, training ammunition utilized during firearm sustainment
and weapon manipulation drills, should also be discarded if it has been
inserted into the chamber more than twice. This practice lessens the
likelihood of a failure to fire or more catastrophic results.