I am a little frustrated. Was hoping the 80 smk would be a little easier to get to shoot tight. Might try some N140 but it should shoot with Varget. I am coming to come back off the lands and see what happens.
I would suggest testing seating depth initially in .005" increments from .005" off the lands to .050" off the lands using 3-shot groups. If there is an optimal window in there, you ought to see it, and you can do it using only 30 rounds total, plus sighters/foulers. Then you can go back later and cover just the apparent optimal widow in a more rigorous fashion, if desired.
I recently did a sort of half-assed load workup with a .223 practice rifle and the Hornady 75 ELDM bullet, solely for the purpose of fire-forming brass. After establishing the charge weight, I tested seating depth in .005" increments from -.010" to -.035" as described above. The shot out of the group low/left at -.025" seating depth was all me, which I recorded. So it is important to keep good records, especially when using 3-shot groups. If you see the reticle move and the shot goes out of the group, you'd better write it down right then. That way, you can have the information available later when evaluating the test results at home. My take from this test was that the 75 ELDMs seemed to want to be seated anywhere from .020" to .035" off the lands.
Because this load was developed solely for the purpose of fire-forming brass, I then went straight to loading some rounds. I used a seating depth of -.020", which was the
longest seating depth within the apparent optimal window. I typically choose the longest optimized seating depth because it affords the greatest amount of land erosion before seating depth will need to be re-visited. I loaded 55 rounds, which I used to sight in at ~318 yd, and then proceeded to shoot 3x15-shot targets (shown below). In fairness, it was stupidly windy that day, I didn't put out my wind flags, and the heavy mirage made it almost impossible to see most of the bullet holes once I had a few shots on each target. Nonetheless, when I went out to recover the targets, they were much better than I would have thought and I'm pretty pleased with how the load shoots. The black circles are 3" in diameter, or slightly under 1 MOA at 318 yd. Had I been using this load in an actual F-TR match with proper wind flags and better shot impact feedback, the results would likely have been even better.
My point here is simply that you should be able to cast a fairly wide net in terms of optimizing seating depth for the 80 SMKs in a manner that doesn't require a huge number of loaded rounds. If you cannot get them shoot tight in your specific setup somewhere between .005" and .050" off the lands, I'd be looking at trying a different bullet. I am not a big fan of taking the path of least resistance, but sometimes it can be the best way to go rather than burning up considerable barrel life trying to get some specific combination to shoot well that really doesn't "want" to.