So this video came out at just the right time for me, since I was in the process of working up two new loads in .308 for the Sierra 155g Palma and the Lapua 155g Scenar. I had previously checked the distance to the lands with my Hornady OAL tool on both bullets last week, so I had a reference point to compare to this new method.
With the Hornady tool I was going by feel to find the point where light pressure just barely engaged the lands. I used the cleaning rod method to go back and forth with the bullet to fine tune position. I measured three different bullets 5 times each for both the Scenars and the Sierras, then averaged the results to get my final number. This is about as accurate as I could make the Hornady tool.
With the method shown in the video I tried to select one bullet that was most representative. I did some quick measuring of bullet length and and base to ogive and selected a bullet that was a nice median measurement for both bullets.
Results were fairly close between the two methods. The Sierras measured about .002" shorter, and the Scenar's measured about .008" shorter to the lands with the video method. I noticed this with the Scenars when using the Hornady tool, there was a less definitive contact point with the lands due to the long sloping nose of the bullet making it harder to "feel" when to stop pushing on the bullet.
Overall I would characterize the difference between the two methods as this... The Hornady method measures "distance to first light contact with the lands", where as the video method measures "distance to first point of complete non-contact with the lands". I certainly think the video method is more accurate and repeatable, and easier once you take the time to pull the bolt firing pin and ejector spring apart.
As a side note, pulling the firing pin and ejector spring is a good exercise to helping feel brass chambering effort. I've been bumping shoulders about .0015 - .002" with a full length sizing die, but it turns out that still leaves some effort required to close the bolt on the brass. I had to size the brass down a fair bit more to get the bolt to close effortlessly. I may end up adjusting how much I size cases based on this experience... I'd never done it before and it was a good piece of info to learn.
Thanks again for putting this video together!