I have had a couple of batches of non corrosive surplus ammo that were quit accurate in anything I shot it out of.
South African, Israeli and some other stuff I believe was made in Finland. All the case had on it was a date stamp The crate had what appeared to be Cyrillic lettering with the same date stamp and Nato stickers.
Sadly I only have a crate of the South African left. As far as the other two, I picked them both up from a now deceased friend along with a couple of crates of Radway Green 7.62x51 and 9x19. I have no idea where he picked it up. The South African came out of Lever Arms back when Alan used to run it and he only had a few crates that came in with some other stuff. I bought two of the five crates he had on hand. In hind sight I should have bought all of it but a shortage of funds held me back.
I tried some Barnaul in my SKS and a Mini 30. It did go bang and fed/ejected well but I was lucky to get the bullets all on target at 100yds. Same for the MFS offering and to top it off, it left so much powder residue behind that it was more difficult to clean than any corrosive I have come across.
As far as shooting non corrosive before and after shooting corrosive, I tried it and it does slow the corrosion down. I watched it closely for a few weeks and after 1-12 days I got a slightly rusty patch and by the 14th day it was definitely rusting.
Maybe the fellow from Quebec shoots a lot or he lives in a very dry area??