A sub-12 rail gun would make all airguns obsolete. But if you put bigger batteries in, or plugged into the mains? Ok, my head hurts too. A great example of where the authorities might for once anticipate emerging technology rather than watch it happen and then retrospectively legislate.
The other big breakthrough is nano-tech pellets slaved to a scope/sensor that's GPS/thermal/radar/all locates the target, assesses the meteorology, and adjusts their flight accordingly - or even homes in on the thermal and/or radar signature of the target even if it moves. And an AI that chooses the moment to shoot for you, and does that.
This is nearing possibility for artillery shells, and rifle bullets will follow. (Bear in mind your smartphone has much, much, more computing power than the Apollo moon missions, and that at 1990 computer processing costs, an IPhone would now cost $1million dollars.) They would cost a lot, but never miss. Which would take all the fun out of it, while being loved by professional pest control guys.
The technology logic is clear. The stuff that needs human skill will become a niche. A nice one. Like archery.
This thread has got weird, but not bad, I hope.