The skill is in lining up the sights on the target and smoothly squeezing the trigger - all while something is doing the same or worse to you.
The difference between shooting a revolver and an automatic pistol is minimal to non-existent - certainly not enough to warrant a skill difference in a game where a +/-1 to a 2d6 roll has a major effect on outcome probability.
I might apply a familiarity penalty in a % based system, but after a few rounds on the range the greater effect on actual combat skill is coolness under fire.
The actual mechanics of loading, unloading, stripping and cleaning pistols can be learned in a few minutes watching youtube...
I'm on the same page as Mike here. With a few points to add:
- We all readily observe (and comment) on the Classic Traveller skill levels; in particular that a level "1" skill is considered competent enough to get professional-level employment in something. Read this as equivalent to being 'certified' or otherwise having demonstrated a level of knowledge to handle not just the "typical" daily events of the task, but for the unusual as well.
Additionally, the whole point of 0-level skills in things like drive, computer and the like is to reflect that the character can function more or less with the basics of said task; but when things go sideways they don't have the background to function as effectively as a pro. For those with an education background, Level 0 falls in that realm of "Conscious Competence", whereas an unskilled person is in the "Unconscious" or "Conscious" Incompetence stage reflected by the die penalty.
Yet - why do we all get so wrapped around applying the same thought to combat skills? And yes, I've been guilty of it too.
For example, I've spent the majority of the past 30 years carrying and using firearms for a living. This includes over a decade as a federal and state certified instructor for handgun, rifle and shotgun; work within the special operations and tactical communities, and duties instructing these skills. Additionally, I've dabbled along the way with combative, to include a few stints here and there with both knife and sword study.
Now - let's realistically examine my skill set in CT terms (although I won't go full cascade, for reasons Mike hit and I'll add to):
Handgun: At my best, in my prime Handgun-3 MAYBE. I was functioning as an instructor a minimum of five full days a month, and doing self-proficiency work at least 8 solid hours a week. From a professional standpoint, I was within the top 5% of what would be considered a peer group on a national scale. Yes, there were definitely people better than me - but they were the ones putting in even more time solely focused on that skill. Today? 1-2 in the same skill - because I don't currently get that practice time.
Rifle: 1-2 MAX. Sure, I was an instructor. I was a competent operator. I was capable of employing the platform from 0-200 meters reliably, and out beyond with the proper equipment and conditions. BUT I was far from an "expert" despite what military award standards say. I was not a designated marksman, sniper, or any of varied other labels. And, quite honestly, if you look at MOST "professionals" they'd be about the same.
Brawling and Blade Combat? 0. I've dabbled - I've used it a few times IRL events. BUT I am far from a "professional" able to make a living off just these skills. This is where the level 0 accurately reflects "competent enough not to completely freeze or do something stupid."
I could go on, but we get the point.
Similarly, to follow on what Mike said, when you're talking 2D6 a +/- 1 is a very significant change. And, quite frankly, like he said the basic "skill set" involved in both marksmanship fundamentals AND employing a firearm under stress and under fire really isn't that hugely different between platforms. Especially once you have the basics down. That's part of why it's easier once you have those fundamentals to learn a new platform - it becomes just another tool in the tool box. Sure, there is a BIG difference between running a revolver and a heavy machine gun - which justifies different skills. But between a semi-auto pistol and a revolver? Really not that much.
Finally, as to the issue of "X generation weapon functions and is loaded different than Y" - IMHO again, that's getting out of the realm of our 2D6 view. We don't penalize someone in their Pilot skill because they're now flying a Solomoni built Free Trader, instead of the Deneb Scout Ship they qualified on - why would we do it on weapons? Yes, if you like getting "crunchy" with things like natural 2/12 rolls, this is a spot to have fun with familiarity. But going down the rabbit hole of "you need 47 different gun combat skills to reflect all these options" defeats the whole intent of the system.
As always, YMMV, and these are just my opinions.