Look carefully at the fired brass for a shiny area. If there is any place in the chamber that has a scratch or low spot the brass will conform to it when fired and have to be rubbed off to extract.
The chamber may look fine but unless you can view it with a borescope it may be difficult to see.
There is another reason but I doubt it is your problem. If a very hot load is fired in the rifle the chamber can bulge in the area just in front of the web. Saw it once in a 7 RUM. The bolt handle rotated easily but case wouldn't extract. A piece of wood placed against the bolt handle and tapped rearward with a hammer was the only way to extract a fire round. The tell tale bright ring just in front of the web was easily seen. The barrel was removed and discarded.
