Inspect that bore with a good bore light to make sure you don't have a hi/lo spot in the rifling. Does a tight cleaning patch go down steadily without any jumps or hesitations on a clean bore? And does the SST go down easy or is it pretty hard to get all the way down? Can you take it down to the powder with one smooth stroke?

That was probably me you read about removing the QLA from a TC Encore barrel. Probably should be a last resort. I'm not familiar enough with an Apex to know if it even has very much of a QL section.

You might try wiping the muzzle good with patch or rag between shots, pushing it down into the bore a bit to make sure you aren't getting some buildup on that end. And depositson that end can have a pretty dramatic effect, IMO. The rifle might shoot better with more stock contact so long as the contact is even on the barrel. And of course all the regular stuff, like letting the barrel cool between shots, being very careful in duplicating your charges and seating pressure, aligning the petals to a reference each time (close anyway), and you might want to adda bore brush stroke before you damp patch/dry patch to reduce fouling even more.

Don't get in a hurry with any part of your procedure and absolutely try to duplicate each step every time.

Just some random thoughts...