Generally speaking, Yes.. My understanding is you want your Ackley Chamber to be .002 shorter on headspace than the parent case that it is derived from. Reason being, you will get good, tight fitting cases after you fire-form. Also, if you dont have a tight, crush fit on the original brass, and it jumps forward during fire-forming, you will like start having a few unexplained missfires...
But, if you plan on buying factory .280 Ackley brass, and not fire-forming, then it wont be nescessary.
.002 is no big deal for a good smith, unless you have engraving or a muzzle brake to keep in time. Then he may want to set it back one complete revolution of the thread shank and go from there...
