Me, I'd start with pulling a couple dry patches through the bore and having a look with a light.
Add a going over the whole works with a screwdriver to see to it that all is snugged up properly.
If you were happy with it 50 rounds ago, and are comparing to that, rather than new (y'know, last fall, not 18000 rounds back) then the odds are, from my perspective, that you have other problems than 'shot out'. Shot out is a rather more cumulatve effect over a long period, to my view.
Whether that's dried mung in the bore, loose screws (scope mounts, esp.), a scope that took a fatal hit at some point in storage, or any of a bunch of other possible issues, it's pretty much going to need you to go through it and sort it out.
Cheers
Trev