Silencers come up from time to time in murder mysteries. Especially, I think, in golden age murder mysteries. They are legitimate, I think, but their use does also raise some legitimate questions.
I was recently reminded of silencers because one featured in Murder At The Vicarage, which is the first Miss Marple novel, published in 1930. Silencers were fairly new technology, back then. The first silencer was developed and sold by Hiram Percy Maxim, an American, in 1902. (He was awarded the patent for it in 1909.) Maxim advertised them regularly in sporting goods magazines and they sold fairly well; they were by no means fantastic by 1930.
The degree to which silencers actually silence a gun, on the other hand, is fairly often a matter of fantasy. It’s not that silencers can’t make a gun silent, or at least very near to it—it’s just that they usually don’t. In order to actually be silent, everything about the gun needs to be designed for it. A really good example of this is the Welrod Mk IIA:
Nothing about this is a normal gun, though. Probably the most important thing—after a well designed silencer—is having a light enough powder load that the bullet is subsonic, i.e. that the bullet travels slower than the speed of sound. This is critical because a bullet traveling at or faster than the speed of sound will produce a sonic boom when it hits the air outside of the barrel. Sonic booms are quite loud. The thing is, the speed of sound isn’t all that fast—under 1,100 feet per second—so typical guns are designed to make their bullets travel much faster. Low speeds make bullet drop a significant problem, and the Welrod’s manual states that it’s accurate in daylight out to about 30 yards. To put this into perspective, my compound bow, whose arrows go at about 260 feet per second, is easily accurate at 40 yards and not that hard to be accurate with at 60 yards. (Normal guns are accurate much further out than bows.)
The Welrod Mk IIA also has a silencer with rubber wipers that the bullet actually shoots through, too, in order to achieve its near-silence. Ordinary silencers do not have anything in the way of the bullet, and in consequence don’t really silence the gun. Ordinary guns fitted with a silencer also tend to fire bullets at between 2,000 and 3,500 feet per second, which will make a loud sonic boom. In consequence, what typical silencers on normal guns actually do is greatly attenuate the noise of the gun from instant-hearing-loss levels of noise to won’t-damage-your-hearing levels of noise. This is an absolutely enormous benefit to the people shooting them, but is not the sort of thing that will make people fifty feet away unaware that a shot has just been fired.
The upshot of all this is that silencers in murder mysteries tend to be unrealistic. What’s even worse is that in stories where a silencer features, people not hearing the shot tends to be a major plot point. Certainly, I’ve never read a story in which the murderer used a silencer only to protect his hearing. To be fair, there’s no reason why a murderer shouldn’t do that—while a murder is obviously not completely risk-averse, they are often at least a bit cautious. That said, that the shot that everyone heard wasn’t merely extremely loud and not mind-bogglingly loud would have no real effect on the plot, and I suspect would be hard to make interesting.
That said, it would be interesting to use a realistic near-silent gun, since it would turn much of the mystery into finding out where the gun came from. Something like a special services assassination gun such as the Welrod Mk IIA or a High Standard HDM pistol would serve well for this. They’re not sold commercially and so they’re not easy to get. Alternatively, a good silencer on a pistol that was loaded with ammunition with a light powder load would be pretty reasonable. It’s common enough for people to load their own bullets in order to save money and this allows people to select any amount of gun powder that they want. It wouldn’t be as silent as a purpose-made special services assassination pistol, but it wouldn’t be too much louder. This would point to someone with more than a little bit of firearms experience, though. Loading your own bullets requires some specialized equipment and a bit of practice. The potential for incriminating an innocent person is, I think, pretty obvious.
This last part put me in mind of other kinds of silent murder weapons, which makes me realize that blow gun darts dipped in fast-acting poison aren’t used nearly often enough in murder mysteries. One would have to find the right poison, but I think that there’s real potential for murderers trying to misdirect the police by using outlandish weapons.