Shot out usually means the barrel rifling is worn out or pitted badly where accuracy is gone.
Check muzzle crowns too. I've seen many times when a new crown has restored accuracy.
When it comes to barrels, rifle or pistol, the higher pressure loads being used such as magnum or 9mm Major, the faster the throat gets worn out.
Might take 100K rounds in pistols to do so, but the beauty is you can replace the barrel.
Most rifles in serious comps gets replaced between 1 to 5K depending on caliber.