No, not Proeliator by John Wales. https://storiesonline.net/s/50903/proeliator
But with similar gunpowder and cannon development chapters.
From memory…
The King or Duke or some sort of royalty went out into the 'wilderness' beyond the usual civilization boundaries with a band of 'merry men' to test gunpowder and cannons.
I cannot remember what the rest of the story was about, just that they wanted to keep the secrets.
This fragment has been lingering on the edge of memory for a couple weeks. Hope someone can help.