As for checking for "brass", I would use a RL example. My Springfield XD has a a "nub" along the top of the slide, just behind the ejection port. When a round is chambered, it pops up. That way, all you have to do us run your finger over the top and know (great for low to zero light conditions) if a round is chambered. Also, there is a small nub on the back of the slide (where the hammer for most other guns are) that sticks out to let you know the weapon has been properly charged.
I remember a Ruger pistol that used a "loaded" indicator. When a round was inserted into the chamber, the back rim of the round would push a small block out of the way, making it stick out the side of the slide. It had a bright red dot on the rear of the block that would get exposed when it was sticking out so the user could see it without adjusting his grip. Worked well enough for standard centerfire rounds.
Unfortunately, someone at Ruger thought it would be a bright idea to put the indicator on some of their rimfire pistols.
Small firearms lesson: Bullets fire when their "primer" is struck, causing a small ignition point which sets off the rest of the propellant. In centerfire rounds, the most common, the primer is in a little divot in the center rear of the case. In a rimfire round, the primer is in a ring around the back rim of the case.
Yeah. A small movable metal block, resting against the rim primer. Imagine what happens if the weapon is dropped and lands on it's "loaded" indicator.
So I suppose even gun "experts" can be stupid about weapon design.
-k
