Do you really need to know anything more? LASER assault rifle?
(ZKZM-500 LASER Assault Rifle)
The ZKZM-500 laser assault rifle is classified as being a non-lethal weapon, like this laser that makes sound that was recently developed by the US military, for now at least because of its low power, and produces an energy beam that can’t be seen by the naked eye but that can pass through windows and cause the “instant carbonisation” of human skin and tissues.
The 15mm calibre weapon weighs three kilos (6.6lb), about the same as an AK-47, and has a range of 800 metres, or half a mile, and could be mounted on cars, boats and planes, and according to the reports it is now ready for mass production with the first units are likely to be given to anti-terrorism squads in the Chinese Armed Police.
You had me at "instant carbonization".
As far as I know, the first instance of the term "laser rifle" comes to us from Poul Anderson, in his 1966 story Door to Anywhere.
The article linked to laser rifle above lists some earlier similar ideas. All with reference quotes, of course.
For style, I'd recommend the Star Trek TOS laser rifle, modeled here by Captain Kirk.
Scroll down for more stories in the same category. (Story submitted 8/19/2018)
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'BY PUSHING AGAINST THE
LITTLE MARTIAN MOON WITH OUR
ROCKET SHIP, WE HAD LESSENED
THE CENTRIFUGAL SPEED THAT
HELD IT BALANCED IN THE SKY.' - Philip Nowlan and D. Calkins, 1930.