I've measured 3x 1 in 8 223 barrels and a 1 in 9.
I just looked back at my notes. All 4 had 77tmks touch the lands at 2.39. 73 elds measured identical. I only measured 69tmks in the 1 in 9 and its also the same. The seating die can be left the same. I expect the ogive profile is more or less the same on these 3.
All the longer sleeks elds (62 VT, 75m, 80 m, 80 x, 88 m) where around 2.49-2.51. Are you sure your notes aren't for one of these? Also I could get any barrel to shoot any of these better than 2 inchs. I tried 4895, varget, staball match, benchmark, 8208, lever, cfe223 as i really wanted the 75s to work.
I will add I've gone away from the Jeffersons in 223. It makes function significantly worse in 223. It feeds alright 100% when bolts worked slowly but if the bolts run fast it only feeds about 80%. The spring is also incredibly stiff and the follower and round impinge directly on the bolt and cause significant bolt bind. Night and day different compared to factory mags.
Seems the grendel etc are different and have feed lips built into the magazine so may be different but the 223 i want to like but end up buying a metal floor plate for factory mags.
I also get 2.39 with just thinning the front bit not notching it. This means rounds are captive in the magazine some aftermarket bottom metals arent guided all the way to the action so a full window can cause feeding issues. I can load to 2.37 in the magazines. Since I've not been able to get any truly long bullets to shoots it doesnt matter for now.
@KyleR1985 does your jeffersons centre feed?