I bought it used, and at first it was shooting 2-3 MOA and I was afraid the barrel was shot out. Then I discovered some loose screws on the frame and got those tightened up. Eventually I had to use blue thread sealant on them. That shoulda been my 1st clue about vibration.....At first I was just using hornady and remington factory ammo to get some brass to reload. The Remington shot better, and it was all Lapua brass which was a bonus. I then started reloading. At first, I was using the Hornady, Lapua, and PPU brass for my reloads, then I found out when I got Quickload and weighed and took H20 volumes on all my brass that the Horndady was only 107 grains H20 while my Lapua was 116 gr H20. The PPU was about 114. I was flabbergasted how much difference there was in the Hornady and the others. I quit using the Hornady and PPU and retired it, though I believe the PPU brass is not all that bad in quality. So, now I use exclusively the Lapua. I went to Peterson on my .300 WM. I am using Lapua Scenar 250 gr. bullets, which are quality high BC bullets. I am shooting N560, N565, N570, and just now got some RL 26 and Retumbo and H1000 to try out. I want to target a velocity of about 2850 to 2900 in the 26 inch bbl., with the 250 gr. bullet. At some point I will try the 300 gr. but not until I get out past 500 yards with it. My best groups before I tried the shaft collar were about 1 MOA, even after reloads, using Lapua Brass, and all the above. After the shaft collar, I began seeing 1/2 to 5/8 size groups with N560 and N565. So, that tells me it had some harmonics that the shaft collar has helped tame. I'm still going to do a lot more load development to get it as low as I can and use a tuner on top of that and cutting recoil should also help. I also tried the Berger VLD elite hunters, but could not get anything to work with those at all. I also shoot some Sierra 2600 Gamekings that shoot just a little worse than the Scenars but are great for hunting. So, the barrel was not shot out, and I got a borescope to confirm that.
I do think the rifle is capable of consistent 1/2 inch groups with more load development and a tuner, and checking all those screws.
If you did not read the 1st post in this thread, you may want to read it too.