> In most times and places, I'd guess the military had many more guns than civilians

My understanding is that the mobilisation for the Civil War is the only time in US history that military stockpiles of firearms have outnumbered civilian gun ownership (although possibly also at the height of WWII).

Though large standing militaries (versus recruiting large numbers of civilians into militias) is a fairly recent phenomenon, so the calculation is often not as cut and dried as one might expect.