"So what is the story with tight custom Chambers"?
When I order a reamer from PT&G, I have them send me a print of a standard SAAMI specifications in that cartridge and another print of Minimum SAAMI spec Match reamer.
I will then take the match reamer print and make changes on dimensions that I deem necessary. For instance, if you look at the dimensions of the print, compare that to the brand of brass that you want to shoot, you may decide to make changes to eliminate the bulge at the base of the case. The Standard SAAMI print MAY indicate of what you can expect from dies and brass, used as a guide only.
Or, you may see that the print indicates that the neck is expanding .007 on the brand of brass you intend to use, which may lead to early case failure(splitting) and you want to change that to a tighter dimension where the brass only expands.002,.003 or .004.
As you measure your favorite brand of brass, and you compare to the print, you may see the potential for massive expansion in the Webb. So, you alter the dimension in the webb so that the brand of brass will better fit the Reamer specs.
In as far as factory chamber dimensions, they are all over the map...and that is an understatement. Also, some European companies have standards that are typical for Europe and American standards may be different(freebore).
Smokepole, when you hear the term of "tight custom chambers", someone might be explaining how he or the gunsmith altered the reamer that they ordered, also it might be just a minimum spec match reamer for that caliber. In addition, the person that mentioned, "tight custom reamer" may be dealing with their first custom rifle that does not have a sloppy chamber, just a std SAAMI chamber.
Once you have worked with a rifle with minimum SAAMI spec chamber installed by a gunsmith that has properly aligned the chamber with the bore, you are spoiled for life(reloaders only).
