This is the 1971 novel Lord of the Red Sun by William T. Silent.
I read this paperback book in the early 1980's but it wasn't in a new condition.
There was a young gunfighter arrived on a frontier world and he goes to a bar and almost immediately is challenged to a fight, he wins.
In this story dueling with firearms is legal. Individuals can choose to wear black bands indicating a willingness to duel. Edvard Jalendra is a 20 year old professional 'duelist' who is hired to challenge individuals to duels as a means of 'assassination'. In the initial bar scene it is not him that wins the fight but another patron that is challenged to a duel by a young man who is being rude. The young man challenges the older man to a fight and the older man wins. There is a later restaurant scene in which Edvard does duel as well and does defeat his opponent.
Saloon gal sits to chat with him
Edvard meets Julane a saloon gal -- but also later implied to likely be a 'joy girl' prostitute -- after rescuing her from two thugs assaulting her in a alley.
and admires his two trusty six-guns, a novelty in a society where the majority use laser pistols in duels.He explains that laser fighters have a tendency to draw very quickly but then 'track in' on their opponents using the visible beam, whereas he, using bullets, has to be instantly accurate and lethal.She chirps on about how noisy they are in use, he explains that this too gives him an advantage because they're startled by the loud noises at the crucial taking aim split second.
His weapons are Rhorrvo-Jenkin'n 11mm automatics and your memory is correct. They are noisier than the typical laser based firearms and provide an advantage in sound as well as not relying on the beam. There is also the impact advantage of the slug. Plus he can have different types of bullets. Explosive, chemical, etc.
Anyways the gunnie then gets involved with a heroic quest group of people and sides with them.
- Mourne and Lori: An Imperial 'fixer' agent and the Emperor's niece who is kidnapped as part of a coup attempt. Mourne is initially sent as her bodyguard.
- Victor Malenkov and Karina: The viscount of Regalio (and the man Edvard was hired to kill) & Karina a noblewoman love interest of Victor's.
One scene I remember is he calls upon a local crime boss for information, the henchman he had ignored and walked past, because the thug was wearing a 'no weapons' armband, suddenly raises a pistol and holds him at gunpoint.He faces this thug and suddenly draws and shoots the guy dead before the baddie can squeeze the trigger, I can't remember what happened next.
The man was wearing a blue band indicating a non-lethal weapon only so was 'cheating'. Edvard draws, fires and kills him in <= .1 seconds. I.e. literally before the other man could register that Edvard had even moved.
Later some of the good team are assailing the top boss compound but are under heavy fire, he charges in on his parallel quest and puts a load of them down.
Yep. Gun battles galore.
I can't remember much more, I do recall a bit about a "no weapons" armband being green whereas the gunslinger people all wear black ones. (I think similar armband issues were also covered in a Heinlein story but this one's not a Heinlein book)
You are correct. A green band is no weapon. Edvard's father wore a green band. Your thoughts about Heinlein are spot on. The first bar scene in which the rude young man finds out simply carrying a gun does not give one the right to be a jerk is exactly in line with Heinlein's quote.
"An armed society is a polite society. Manners are good when one may have to back up his acts with his life." ― Robert A. Heinlein, Beyond This Horizon"
The description on the site is pretty accurate. it is not an in-depth SF novel. But as a galactic swashbuckling romp it is not bad.
"Another futuristic mash which may cause the Galactic Empire to sink beneath a ziggurat of pulp. It's about a fanatic's attempt to cause war between the Empire and the Kingdom of Talnar through assassinations and kidnappings. But the author is mainly interested in transparent clothing, nudity, and the antiseptic capers of three pairs of lovers. Bosh."