Have done loads of ladder tests with various cartridges but have never run into this "problem". Modern 6.5 x 55 Swede Mauser SE 130 Berger at lands Kreiger 30 inch 8 twist bbl with brake on Kelbly Atlas action, all smithed at Kelbly's 10 rounds IMR 4064 powder beginning with 40.3 and increasing .3 with every shot to 43.0 gns. Pre thunderstorm "dead calm" temp 75 humidity 70...estimated All 10 rounds formed a ROUND one inch group at 300 yds... no vertical stringing to speak of. What is this group telling me? Had almost the same results with Re15. 4350 was a joke. Love the results, just don't understand them.