I have a rifle that just won't extract a particular brand of ammo. I haven't measured yet, but I suspect it's a rim thickness thing.
Fiddling with extractors is not easy. It doesn't take but one errant stroke of the file to spoil one. Ask me how I know!
If you haven't already, blast the extractor out with brake cleaner and re-lube. If it's gummy it won't work well. You might also try putting solid forward pressure on the bolt handle when unlocking the bolt. It fixed the problem (sort of) on my problem gun.
