I forget which book it was but there was admission at some point that Dresden's reliance on revolvers due to their simplicity wasn't really necessary, and was a result of Harry's relative ignorance on guns at the start of the series or something.
It was Harry's ignorance, but admittedly he was parroting a very common prejudice against semi-automatics from revolver enthusiasts. The theory is that Semiautomatics statistically jam significantly more than revolvers (which are nearly impossible to jam); and to a wizard any such difference would be magnified by the Murphionic effect on all wizards. This is a common prejudice in a world (both RL and DF) were "Tried and True" rules because their lives are on the line, and trust comes slow. It took a long time for modern magazine designed to win over various police forces, for example. This was Murphy's point in SG, that actual, current, 21st century ones have largely solved the jamming issues.
BUT: Even though there existed electric lights in The Deeps strong enough to withstand a wizard duel, Marcone and Gard still decided to control their bombs with clockwork. When you have people running around who subconsciously warp reality itself so much that technology breaks near them (my interpretation of the murphionic effect), the risk assessment calculations change a great deal.
We've seen alot of Wardens etc pack some pretty serious firepower throughout the series. So question is, when is Dresden going to get an assault rifle or something.
His enemies certainly use them. Micheal of course got the bad end of that. Seems about time Dresden and crew assault rifle up on the reg.
Actually this is part of an even bigger question of mine that I have wondered for some time. I can see why dresden doesnt pack a long gun everywhere since it would be inconvenient compared to a pistol. Although there have been a number of situations in the book where It might have been a good idea to get a rifle since he knew what he was going into. Context would be the determiner etc.
But how come the WC doesn't use full on geared out Wardens on high-end missions? Like it would seem totally logical to have Wardens who are going to war with the Ramps (for example) to basically just look like soldiers from any mortal army, save they can also do magic.
In some ways they do, Changes showed that the Council wears modern military harnesses, with the speculation by Harry that modern military harnesses are actually modeled after the Council's gear.
As far as firearms (and grenades, etc) it always described as a generation gap: There is the Old Guard, most of which predate the invention of modern semi-automatic weapon, and the New Guard who are far more progressive thinkers and all carry modern military weapons (Carlos is the poster-boy for this group on page, but there are always mentions of there being plenty of others. The change is happening, and the War presumably forced them to shed a lot of pointless habits, but this is still a gerontocratic organization where the average age is measured in centuries, and most of the member predate the widespread use of electricity, and as a collective whole they tend to think they already know everything worth knowing, and know it better than anyone else alive.
So in other words, it's the same reason my grandmother refuses to get a cell phone: she lasted this long without one and doesnt need some young buck telling her what to do.