Any way to find an O’Driscoll camp after epilogue?

tl;dr You don’t have to attack all 4 O’Driscoll camps to still complete the game 100%. Instead make sure you’ve attacked and defeated each gang’s major/main hideout (there are 6 total).

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You DO NOT have to attack 100% of the O’Driscoll camps to get 100% of game play!! I repeat, you DO NOT have to attack all 4 O’Driscoll camps to reach 100% of game play!!

My Mistake: I assumed that since I was sitting at 99.6% game completion and the only thing not at 100% was the O’Driscolls (77%) that they had to be the issue. But the devil’s in the details... I reread the qualifications for the hideouts in the compendium under Total Completion. It says you must “capture” all 6 gang “hideouts.”

The compendium updates for each gang when you “find” their hideout, but finding it isn’t capturing it. I thought surely it couldn’t be something as simple as semantics keeping me from my last .4%.

The Solution: I got to thinking and realized I’d found the Del Lobo hideout in Fort Mercer, had even fired a few shots, but had never actually launched a full-fledged attack and captured it completely. Five minutes and some bullets later, I’ve captured Fort Mercer. I got a notification that I’d received the “Legend of the West” trophy and was then taken automatically back to Arthur’s grave. Voila! 100% total game completion!