Well now that I have a 6mm Creedmoor I understand what you guys are talking about with some of the feeding issues. If I try to chamber a Berger 105 VLD Hunting bullet seated at mag length it jams into the barrel below the chamber if run slow. If I run fast then it chambers but deforms the meplat and almost closes the hollow point e.g. useless for hunting. If I chamber a Hornady 108 ELDM at mag length it will slightly contact the barrel below the chamber but will chamber the round even running slow and the polymer tip doesn't deform since it can take a bit of a hit during chambering and keep its shape. Shorter bullets do not have this issue like 70 or 87 grain bullets and this is because the case shoulder hits the feed ramps before the bullet hits the barrel. So looking at this, I think the problem is the distance from the barrel face to the outside of the extension being to short for modern high BC bullets. I think if they extended this space and made the bolt accordingly this could solve this type of feeding issues, not the floppy mag problems though.
I checked my 308 barrel after all of this and I can see where the bullet is just kissing the barrel face, maybe 0.010" to 0.015" below the chamber. With the 6mm its half the barrel thickness at the chamber.