https://palmettostatearmory.com/psa-ak- ... rrier.html

I think that's the fundamental problem with trying to make AK's here, it was a gun designed to be made on 80 year old machines and lax tolerances. Of course you want to be able to just churn parts out on CNC machines. From my understanding, they were all hand-fitted to a certain degree during assembly. Hard to find people with those skills or the capacity to learn them in the USA in the 21st century. It's made to be reliable and made in mass quantities, not to be particularly accurate. I remember how hard it was just trying to get on paper with my brand new Arsenal Bulgarian AK. Best you could buy in 2009, still terrible. They are what they are.
I believe the 5.45 one's do use a thin stem bolt. I've only seen one in person once, and it was a little while back so its a little fuzzy but I believe it was a thin stem bolt.