I don't have any data on factory ammos in my new Shilen Barrel 0.223, but in its predecessor factory barrel, factory ammos tended to be less accurate by 24.3% compared to my handloads tuned for Optimum Bullet Time.
All these averages are based upon 5-round groups at 100 yards.
I recognize that every barrel will be slightly different in its preferences for bullets, but hopefully this will provide at least some data for comparison.
The 77g Berger OTM bullets are the 8th most accurate bullet (0.2133 average for 24 groups) in my new Shilen barrel .223.
The best 77 gr bullets, the Sierra TMKs, average about 0.0046 better on average.
The top 5 bullet types are:
90 gr Berger VLDs (0.2046) for 12 groups
73 gr Berger BTTs (0.2047) for 40 groups
69 SMKs (0.2070) for 19 groups
77 TMKs (0.2087) for 11 groups
80 SMKs (0.2088) for 24 groups.
All of those averages include all of my 'shooter induced variations' which result in the average group size for all bullet types to 0.2164.
Most of those larger groups were shot early when the barrel may have been breaking in, or the shooter was figuring out seating depths and such.
If I remove the most egregiously 'messed up groups', those over 0.226, the overall average group size drops to 0.1974 for all bullet types.
Considering only the most consistent groups, the 77 OTMs drop to the 11th best with an average of 0.2026.
The top 9 bullets all average under 0.195 and the 10th best averages 0.2001.
The top 5 bullets when the larger 'shooter induced variation' groups are not considered, also change slightly:
80 gr Hornady ELD-Ms (0.1706) for 30 groups
80 gr Berger VLDs (0.1894) for 15 groups
73 gr Berger BTTs (0.1901) for 29 groups
77 gr Sierra TMKs (0.1917) for 7 groups
80 gr Sierra SMKs (0.1923 for 17 groups
I hope this helps to put bullet performance in perspective, even if I didn't really answer the question on factory ammo.