I was thoroughly enjoying a book the other night, one of those police thrillers where the author makes much use of his protagonist's mental processes and internal conflicts.
But when the bad guy started a chapter poking someone in the back with a hunting rifle things took turn for the worse. Not in the plot, which was nicely convoluted, and not in the handling of the situation, which was rather nicely constructed.
A couple of pages later it had become a two-barrelled hunting rifle. (This is not a technical impossibility, but relatively unlikely.) There should be a reason for giving your character such a piece of exotica, and in this case there wasn't.
What the policewoman took away from him at the end of the chapter was a shotgun.
I would love to own - or even just briefly handle - such an amazingly versatile thee-in-one weapon. A veritable chameleon amongst firearms ;-)
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Now... You may think this doesn't matter, that 'the average reader' really doesn't give a damn about these things.. You may well be right, but if you believe this then just stick to labelling the weapon as a generic 'gun' in your own writing.
You want people to enjoy the story, not stumble over inexplicable changes. It's nearly as bad as a character being mis-named, which creates the impression that an extra player has just suddenly joined the cast. It takes the reader away from the flow of storytelling.
A 'rusty but still menacing shotgun' is a fine description, which avoids any need for technical details. An 'oily and deadly looking' handgun saves you from even having to mention whether its an automatic or revolver. Note that both of these are describing it from a character's viewpoint, specifically the character on the wrong end.
Unless the potential victim is a trained firearms user or collector the exact details are likely to escape them when under threat ;-)
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Think about this when you write a scene involving firearms. If you need technical details do your research.
Never be afraid to use the 'generic' weapons. In cowboy novels, for example, there are three makes which every reader recognises almost without needing to think about it, Winchester (lever action rifle), Sharps (the big buffalo gun), and Colt revolvers. When the author introduces anything else it's usually a relevant plot twist. (Or a personal favourite they feel compelled to slip in.)
Gyppo