Ok, time out.
The manufacturer states that parts are individually hand-fitted for tighter tolerances.
That's not how it works. Either they can build the parts to standard, or they can't.
Tolerances are whatever you say they are, especially if they are ISO cert. All ISO does is certify whatever you say your standards are, they are, but only if you document it. That's all.
So, if someone says they have "tight tolerances," well, ain't that nice. What numbers do they say they are using? What do they mean, and are they even any good?
Tolerances of plus and minus .030" aren't much to write home about, and .015" is pretty normal for combat guns. Are they going even smaller? Fine - which then leaves me asking, why do they have to hand file the part to fit if it's already within .015?
In the day, the reason you hand fitted the parts (and why you still have to for 1911's,) is that the parts don't hold a tolerance within the window of functioning if they were just put together. All those wonderful Pre '64 Winchester HAD to be hand fitted because the parts were actually pretty horrible and couldn't hold a working tolerance.
Note very carefully - you buy parts for an AR15, you get parts that work together regardless if they came from 5 different sources. Like mine. Can't do that with the 1911. Apparently, you can't do that with this maker, either.
This doesn't have anything to do with clearances - which is the space a gun has to have for the parts to actually work with each other and not hang up. Oh, look, the 1911 again. Get a rattly loose one that you can shake the slide and see the front sight tip from side to side, sure, standard issue in the day, even after an arsenal rework. Plenty of us shot them Expert. Tighten up the clearances and oops, it starts hanging up and you get FTF and FTE - like all the new ones.
AR15 - same thing. You can have enough slop between the upper and lower receiver to insert playing cards, it will still shoot expert. Ask me how I know. Add orings, wedges, whatever, and all you do is think it's better - it's still a 2MOA barrel. That's all the Army asked for, and all they issue.
You can tighten up the tolerances all day, but it's expensive. What gun makers do is measure that batch and combine it with other parts that are also in tolerance - and which, when assembled, meet the tolerances for the assembly. Do that, the assemblies work better. If you don't, you can stack up a whole bunch of tight tolerance parts and still be OUT of tolerance as an assembly.
What it sounds like is these guys then pass a file on the important surfaces and get them back. In which case what you are really seeing is that it was cheaper to do it by hand than make the parts conform to the window in the first place. That's not a good testimony of the quality manufacture of parts. It really means either the tooling is in poor shape, or the operators don't know what they are doing.
Having spent time on the production floor making parts on an Amada 100 ton brake press, and working for a contractor expediting battery production for Dept. of Defense powered projectiles, you get an understanding of what tolerances, clearances, and marketing hype is. From my perspective, a gun maker claiming tighter tolerances and hand fit assembly is a gun maker talking out of two sides of their face at the same time.
What's nice is that it doesn't mean any thing about the product. It stands on it's own reputation, it either shoots or it doesn't. Enjoy it for what it is, not what marketing claims is going on. Frankly, those guys are the last ones I would ask.
