The AR-15 accuracy project rifle displayed a wonky pattern on the muzzle crown after a disappointing first day at the range. Perhaps it was part of the issue with this rifle throwing patterns instead of groups, or perhaps not. In either case, It's no longer an issue.
Using a chamfer kit purchased from Brownells a lifetime ago, the first step after cleaning the muzzle was to square the face of the barrel at 90 degrees.
With the .22 pilot fitted to the cutting head, and a bit of lube applied, the cutter was turned by hand while applying light pressure. Stopping to clean every few turns, it took only minutes to get what I was looking for. The next step, after cleaning the bore once again, was to set up the 11 degree cutter and repeat the job till the rifling ended cleanly at the muzzle.
Once again, the barrel was scrubbed, and then a thread protector screwed on to.. well.... protect the threads. The next step is a range test, to see if this work has any effect at all on the fliers and lack of accuracy. Easy peasy, if this was all it was!