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There is a system designed for making dry-fire practice more effective for gun owners at home. The heart of it is a fake cartridge that is loaded into the chamber of the firearm in question. In the nose of the fake cartridge is a laser diode; in the body is a watch battery; in the head of the fake cartridge, in place of the primer, is a pushbutton switch that turns on the laser when pressed.
To use it, you aim the gun at a target and pull the trigger, dropping the firing pin on the pushbutton "primer" and shining the laser on the target, where the spot is observed and scored somehow.
However, there is a weakness.
Different guns are designed differently, and one of the differences is in the way the firing pin works. Ideally, the firing pin would punch the "primer" for a dozen milliseconds or so, making a dot on the target long enough for the scoring system to observe it, but not long enough for shooter unsteadiness to slash a curve across the target and make scoring ambiguous.
But some guns have firing pin springs too weak for that: instead of one flash, they bounce on the "primer" and create several flashes for each shot, which are scored separately.
Other guns have very strong firing pin springs that, when fired, keep the "primer" pressed and the laser on like a flashlight, until the action is recocked.
This circuit should go inside the fake cartridge. Any shot, whether it produces a very brief contact, a series of bounced contacts, or a single long contact, will be converted into one nice square predictable-length pulse.
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