I would not believe his tale of 1" groups. A typical 7.62x39 AK will deliver 3-5 inches. There are not high quality match loads available. Wolf, Barnaul, etc. are delivering that kind of accuracy.
Repeatable 5 shot groups are what is required to make that kind of claim. I would settle for seeing repeatable 3 shot groups, but it will not happen because AKs do not deliver that kind of accuracy.
It will shoot consistent 3 shot groups just over an inch from a cold barrel with hornaday vmax, As the barrel heats up it will start throwing flyers 5 shots will go to 3-4 inch. It is not a bench rest gun and I'm not claiming it to be. So I do not need to have repeatable 5 shot groups to make that claim. So, maybe between the milled reciever, trigger work I have done, the shaw barrel & my ability, maybe just maybe it is possible to put 3 shots close to an inch..
Joe