I would certainly agree that “custom” best describes a gun fitted to the end user. I think SZ summed it up well.
A gun can be fitted, but be of entirely standard, "non custom" components. IOW, you can re-fit a production BP gun for a smaller shooter, perhaps even lengthen it for a taller shooter, or "fit up" a standard mass-production company kit. I would not call it custom (or semi-custom). I'd call it a production gun (or kit), fitted.
More mud!
So you order a kit, and swap out the lock for a more appropriate one, and add some tacks to it, or a square nail or three, and spend a month building up a fantastic finish on both wood and metal? Custom? or simply a well-executed "kit".
Mud.
Was the kit one of thousands cranked out by production guns inc., or was it some special and appropriate parts gathered up by a one-man shop and sold to you because you're "in a hurry" and his wait list is two years? In-fact it was one of seven kits he sold that year.
Mudlicious. No disparagement intended for any such gun of any type or the makers/sellers/assemblers of such. I like to judge them when I see them, not before-a gunmaker can-and sometimes does work from all sorts of sources.
Those retailers using such labels are probably the best folks to ask exactly what do they mean by their labels. We don't have a "standardization".
similar but different: "Bespoke" was the term most often used in the hand-made bike world for bikes ordered by individuals and quite-naturally fitted to them. Also there are plenty of hand-made, spec bikes that are fantastic and work within for the inherent-fitment adjustments available on those machines.
