I have had different lots of Norinco 5.56 and it has been everything from very good to abysmal. The first two cases, which were from the same lot, was some of the most accurate and consistent factory ammo I have shot. The next case was terrible in just about every way. Poor accuracy, crooked necks, etc. When I went to decap some of the primers in the second batch it soon became obvious that some of the flash holes were punched off center. I just shot the stuff and chucked the brass from that case.
Surprisingly the next case with the same date stamp but different lot numbers on the boxes was again very good. I picked a half dozen boxes of 20 randomly through the crate and they were every bit as good as the first but much older batch.
I went through about 300 rounds on the bad crate and stopped there. I pulled the bullets and reclaimed the powder which is identical in burn rate to BLC which is an old Higginson's powder that I like a lot in small rifle cases up to and including 308win.
I weighed those bullets to see how consistent they were and all were within a tenth of a grain. That is very consistent. The powder charges were all within a tenth of a grain as well. 25.4 grains +- .005 grains. That is closer than my powder measure will meter the charges.
As far as the brass on the three good batches I have goes, It is all very consistent as far as weight/stretching goes. I also use a small base die because the rifles I shoot all have minimum spec chambers. I have barrel stubs with chambers cut in them that match the rifle chambers which were cut with the same reamer. I have loaded some of those cases over a dozen times without an issue.
To tell the truth, the material the cases are made from are some of the best for reloading I have used. It doesn't seem to work harden at all and I have only had to trim after 8 firings. I am fussy when it comes to loading for accuracy. In fact I have been told I am anal. If the Chinese brass wasn't doing the job I wouldn't waste my precious time on it.
You may have a bad batch as was mentioned above. I have two more crates of Norinco factory loads from this lot and date set. They will likely last longer than I will.
The best surplus brass I have ever used was South African. About 20 years ago a bunch of it came into International and I picked up several cases. I hoard that stuff for special shoots. The consistency from that stuff is as good as my handloads.