To Ron in VA. I would be happy with that.
I happen to have more work than one person can handle. It is not a matter of that I have to take every job that comes in the door. What I need is more time. The pleasure of owning your own business is that you can turn away the tire kickers who's only criteria is how cheaply it can be done. Gunsmithing is only half the business. The other half is stocking quality parts that I know I can trust to put my name and reputation on. Your reputation is EVERYTHING in this business. When you start taking jobs just for the money, and do not care what the out come is from the miss mash of parts brought to you, you will loose more customers than the few you turn away. Believe me. Your name is on every gun you touch. Weather you engrave it on the barrel or not. If it turns to crap you think that owner of the gun is going to accept responsibility? Ian_Owen gave a perfect example of this in his post. You can bet that Mr. Crap Parts will tell everyone he knows what a lousy job your did and never mentioning he supplied the junk.
If you do not stock anything or want to supply the parts of the build, then the customer has to supply the components. If you are doing work for retail sport shops then I would expect them to supply what they can. They are in the business to retail and you know that up front. Your business relationship with them is symbiotic. I do not pad the job with over priced parts. I know who my good and repeat customers are. When they have a problem with one of their guns the week before hunting season or just before an important match they will be moved to the head of the line. That is the long term relationships that carries your business through the lean times.
I've quoted all this because I think I understand, and agree with your decision. Our small (5-man shop) is in a similar situation, except with setting type. We are specialized. That means (1) we charge a bit more, and (2) only work for a certain group of people (academic book publishers).
There are almost never any misunderstandings when we turn down work, because contrary to what you may think from my postings on BR Central, I will, if needed, take the time to tell people or other publishers why their job doesn't fit our business. That can well be for quality issues, they've selected a typeface that can't be used successfully, have a design that would, in my opinion, reflect poorly on our shop (tricky when it's the guy's wife who designed it), & on & on.
Most of the time, it's easy -- for example, they don't have an editor, and we won't/can't supply one. But occasionally I wind up taking several hours explaining to/showing why we won't take someone's job. I also try to help them find a shop who will do a reasonable job for them, given their situation, at a reasonable price.
Of course, from time to time I fail, & they go away mad. But that's not too often, and at least I tried.
For all I know, that's what you do & are just using BR Central to vent a bit. If not, I'd recommend the above approach, even with it's cost of unbillable time. In the long run, it can get you more of the kind of business you want to do.