Playing as Pachacuti. Did not post in bugs as I am not sure for reasons below. I was building up my niter cache to upgrade a swordsman. I hit 18 on turn 195. On the next turn I go to upgrade and I had 0. I did not remember a trade. Figured I spaced it. So I roll back to the auto save for 195. I go through my turn on 195, click next and as it rolls through all the other civs. My niter goes to 20 and then back to 0 on my turn's start. Can you upgrade upon researching gun powder regardless of niter? By this I mean, I upgraded two swordsman. Did it credit me the niter cost? I might have thought this, but it was not in a city with Magnus. I know that is not exactly his benefit. Plus, I have given him that promotion. After that, I hot my next 20 count of niter and exceeded it.