I have a Sako .223 converted to the A I configuration and I have a problem with cases failing to extract. In fact I am unable to open the bolt unless I give it a sharp rap with a wood block or soft mallet. I tried a detailed cleaning of the chamber and bolt recesses and believe that all is clean. Next I pulled the striker from the bolt , added a coating of J B paste to a fired case and "worked" the case into the chamber about fifty strokes. The case took on a very fine "sanded" appearance over the front 1/3 and rear 1/3 with an un affected portion in the middle. I measured case diameter all along the length and it tapers smoothly ( as well as I can Mike it).Next I cleaned all, reassembled, applied a very light coat of oil to bolt and fired ten rounds. Two were hard to extract but yielded to a sharp palm stroke. Before I go any further with this I would ask if any other LRH members have any clues or suggestions?