Failing to chamber.

[noone]

Here is what I would check:
1. Length to a datum line on the shoulder of a fired case
2. Compare that length to the length of your sized rounds at the same datum line
3. Check distance to ogive on the bullet you are using. You may be jamming the bullets into the throat, either because of a
short throat, or seating the bullets out too long for the ogive of the bullet you use.
4. Check extractor, and ejector to see if they both allow the cartridge to seat fully into the recess inside the bolt. Also insure
that the rounds aren't pressed too tightly to the opposite side of the bolt by an over powerful extractor, and that the
ejector works properly.
5. Insure that the chamber and throat are free from all carbon, and copper fouling.
6. Then I would smoke an unloaded dummy round with a candle, and see where the soot is removed by either the lands, or
by something pushing on the shoulder of the brass case. If you see clear signs of the rifling on the bullet's ogive, your
bullet may be jammed into the throat. This can cause difficulty chambering, and difficulty extracting unfired rounds.