As a veteran of one factory Tikka barrel removal, I'd recommend a minimum of one week spent soaking the tenon threads with penetrating oil from inside the action (can even couple this with mildly heating the action with a heat gun), a barrel vise cranked down TIGHT, an action wrench clamped on TIGHT as close to the barrel as you can get it, as long of a handle/cheater as you can find on the action wrench, and a ~3 pound shop hammer.
If I was going to do it again, I'd have a second person to load the action wrench to a couple hundred foot pounds (not exaggerating), then whack the hell out of the action wrench handle with the shop hammer in an effort to "shock" the threaded interface into coming loose.
Or pay someone with a lathe to make a relief cut.