I have. First, I would buy a set of clip on front/rear sights because the POI is going to be way off from where the bead sight will be. Once you can zero the sights, the accuracy is not much different than a single shot rifle.
That said, get inserts that shoot worthwhile calibers, i.e. not .22 or .380. You can get a single shot .22 rifle for almost as much as the insert, but it will be lighter and more reliable. 9mm is fine, but if you already have a PCC in 9mm, kind of pointless. Something like .357, .44 Mag would be a lot better, especially in those 8 inch or longer adapters.
MCA Sports makes 12 gauge adapters in .30-30, .30-40, and .45-70 and if you keep the range to under 150 yards, they're a lot more practical for hunting, but that ammo isn't cheap.
If this is strictly for cheap fun, 9mm (when it's normal times) .40 and .45 ACP and whatever other cheap centerfire ammo you can get is fine. If this is for more than cheap fun, SHTF/TEOTWAKI/Boogerloo, get adapters for common calibers and adapters for working calibers like .30-30, .45-70, .357/.44.