FWIW, I went looking for KNO3 today at Theisen's (local farm supply store).
I found Gordon's Stump Killer right off the bat. It was, however a liquid, and, with the help of someone else's eyeballs, it seems that primary ingredient is Glyphosate (Round-Up weed killer). However, I then found a 1# jar of Gordon's Stump Remover which was some sort of crystals, and did not have any ingredients listed on the label. But it the MSD sheet for it lists it as 99% KNO3, so exactly what I needed for under $8.
Many thanks to Cameron for the suggestion. I will be bluing some screws this weekend as I just got my engraved parts back from Turnbull yesterday.
Remember, is the Stump REMOVER, not Killer that you want.
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
