Agreed regarding finding the flat spot.
I have been running the 200 MKs 2nd gen for my third season now.
Despite a piss-poor performance in judging wind changes this past weekend at Nokomis, I think I've had reasonable success with these 200 MKs given that I have only 5 years in F T/R.
I have flat spots at the 41.8 grn Varget and another with 43.0 Varget.
After 43.2 I am starting to compress loads in my fireformed 308 Lapua Palma cases.
As luck (maybe science ?) would have it, my ES with 43 Varget are around 7-9 fps on most 15 round strings..... BTW at 43.0 I am doing 2,660 fps with my 30 inch Kreiger 1:9.
I also agree that seat depth testing comes second after finding the best charge weight.
I have to disagree, however, that you test in increments of 0.003 depths.... IMO this is where you will burn up components needlessly.
For long pointy bullets (or any bullets for that matter) I follow something similar to what Berger recommends for tuning their VLDs.....my exception is that I generally never do any kind of seating Jam.
I've never had a gun (chamber) that has ever seemed like a Jam .... they all have grouped like absolute sh#te.
https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/
After I found 43 varget as my go-to charge, I loaded 5 rounds (Berger recommends 6) of each at :
0.000 on the lands ...
0.010 jump ...
0.020 jump...
0.030 jump
0.040 jump
0.050 jump
Just like Berger has stated in their VLD article -one of these groups will (it really WILL) be
way better than all of the others.
In my case, it was 0.030 jump.
So the next range trip I then made 5 more rounds @ 0.025 ... 0.030 ... 0.035
I had observed that 0.025 and the 0.030 were very similar in group size...... so I took a point in between these two "sweet spots" and now my go-to seating depth is 0.028
I know of 2 other guys that use the 200 MKs that compete here in Saskatchewan F T/R and they are both around the 0.030 jump.
Another thing that I have overserved regarding 2nd gen 200 MK is that Sierra really means it when they recommend a 1:9 twist..... I have a sneaking suspicion that most guys who have experimented with this projectile and had a bad experience were trying to use 1:10 or slower twist rates.... might be fine for Berger 200s but now the Sierrra's.