CM-84E - Lesson Learned

[Mark Briggs]

This note is intended as something of a reminder or gentle warning for CM-84E free pistol owners. Yes, what's written here is just good plain common sense, but every once in a while we humans make the odd slip, so it's nice to have a reminder before we make that little "oops"... ;-)

A local shooter complained that his CM-84E would often fire when he closed the breech on a loaded cartridge. I disassembled and thoroughly cleaned his pistol, working on the belief the sear area was likely contaminated with dirt, preventing full sear engagement. Following this cleaning all went well for a short while and then the pistol resumed its old habit of firing as the breech was closed. Hmmm, said I, puzzling indeed!

Another local shooter spent a fair amount of time disassembling and studying the particular CM-84E in question and could find nothing obviously wrong with it, and then stumbled upon a simple but important truth. It would appear that our friend never removed his finger from the trigger guard, even when loading the pistol. As an experienced FP shooter the chances of him actually touching the trigger accidentally were slight. However his finger was positioned so that it constantly blocked the light beam of the safety circuit. Under normal circumstances a shooter would remove his or her finger from the trigger guard when loading. Vibrations etc associated with loading the pistol are great enough to cause the trigger switch to toggle when low trigger weights are used. The light beam safety circuit prevents these unintentional triggerings from actually causing a shot to be fired because the electronics require both the trigger circuit to be completed (ie the trigger actuated) AND the light beem to be broken by a finger in order to energize the solenoid and fire the pistol. With the light beam blocked this safety circuit is effectively disabled. Any vibration of the pistol can jiggle the trigger enough to actuate the trigger switch. When this happens (there's often enough vibration to do this during the loading process) a shot is fired. If you're lucky, it goes into the dirt and only costs you 10 points. If you're not lucky, let's not contemplate the possible outcomes!

The lesson to be learned here is simple and likely obvious to many. When loading the pistol, keep your fingers out of the trigger guard and let the light beam safety circuit do its job!

[terrypchan]

Thanks for the helpful tip.

It should be also pointed out that this warning is also clearly stated in the all too terse CM84E manual. Section 2.3. Loading and Firing.

"... paying attention that your trigger finger is clear of the optical sensor line, otherwise the shot may be fired accidentally caused by vibration during the loading procedure..."

[Fred Mannis]

which is the second of the three key (NRA) Safety Rules

Shooters involved in the action pistol disciplines as well as law enforcement personnel are all taught to keep their finger out of the trigger guard until just before firing. And this is with trigger pulls ranging from four to, perhaps, ten pounds.

In an IPSC or IDPA match, being caught with your finger inside the trigger guard at any time other than just before firing is cause for being disqualified in the match. I guess FP rules are not as strict.