May I ask how you determined that the cases were hitting the chamber?
In most chambers that are SAAMI spec, even at the max case length, there will be .020" of room before the neck will touch the throat.
In regard to your COAL not being consistent, it may be at the ogive but not at the tip due to the plastic tip. As stated above, get yourself a comparator and measure off the ogive for consistency. Unless your seater plug is the wrong shape/depth, it should seat your bullets consistently in regard to base to ogive length.