I have reviewed your video. The cure is very simple. Contrary to popular belief, controlled round feed actions require quite a bit of tuning in order to function properly. It is much simpler to make a push feed action work perfectly.
When a cartridge is fully chambered, the extractor should be tight enough to hold the cartridge head against the opposite side of the U-shaped recess on the bolt face. The extractor must have positive tension to push the brass against the opposite side of the bolt's face.
On your rifle that is not happening. You can test it by removing your bolt and slipping a cartridge's head up under the extractor.
Proper fit has nothing to do with the case head diameter. Rather it depends on the diameter of the case's extractor groove. Manufacturers dimensions vary a lot. I mean greatly. They don't pay much attention to this dimension because is does not alter the function of push feed actions.
The most persnickety guy I know about feeding, DArcy Echols, adjusts the extractor's tension to a specific brand of brass. That is one reason why his rifles function perfectly. So you may solve your problem by switching to cases with a larger diameter extractor groove. I wouldn't be too quick to blame Kimber. Alternatively, you could get a 223 extractor and fit it to a specific brand of brass.
Last edited by RinB; 02/14/17.
