In praise of small gaps...
My personal .38snubbie has a .002" gap. I like it like that. True, towards the end of a 50-rd box of ammo the trigger starts feeling gritty
but a quick wipe to the back of the barrel and front of the cylinder clears it up for another 30 or 40 rounds at least
.
.38Spl from a 2" barrel is marginal stuff. I want all the velocity I can get. I keep it loaded with two 5rd speedloaders handy so in 15 rounds it's not going to gum up.
In a wilderness survival gun and a more serious caliber and barrel length, I can see going to .003" or even .004". More than that isn't optimal. More than .007" is a malfunction.
If you end up with one that's too tight, at .001" or you want more than .002", DO NOT send it back to the factory! I wouldn't. God only knows what it'll come back at.
Instead, if it was me, I'd take a fine-grit knife sharpening stone and very gently polish the back of the barrel. Go dead slow, keep it nice and flat, take light strokes and you'll get it to where you want. This is the easiest home gunsmithing fix there is, and will allow you to set the gap to YOUR needs.
Don't look at a "too tight" gun as a problem. If you find such a critter at your gun dealer, look at it as a wonderful opportunity to set the gap to perfection.