I asked Bill Smallwood of Parker Hale if he had seen it used before and this was his reply:
Yes I have seen it, when we build a custom rifle in .308/7.62 we chamber it .308 non standard, this is done with a target reamer which has tighter tolerences, (neck,throat etc.) this gives for greater accuracy but will make the standard 7.62 round hard to extract some times, when we chamber in the none standard .308 chamber we submit it to proof with all the correct measurements and they stamp it as .308 NONE STANDARD and add the neck, and throat size, there are 3 different measurements but i will get them e-mail them to you. This chamber will benefit you if you home load
That in part answers the sticking issue which I hope the GGG will resolve