Buy a Weatherby sub moa Vanguard. They always work.
Attached photo of my Wby V2 group in 6.5 Swede, 5 shots @ 100yds
I have read all 7 pages and you have a ton of really good info to sort through... here is my .02c for what its worth
Your primary issue seems to be speed variance.. you have ruled out a bad chronograph.. excellent.
Next, you hand load, like I do, so humor me please.
Throw 4 or 5 loads and check them on someone else's scale, that will eliminate a scale issue. And you didn't mention, single stage press or progressive?
My gut is telling me inconsistent charges..however, that could be powder charge weight variance or bad blend of powder.
I work for the Canadian Distributor for Bergara on a part time basis. Mind you.. he is the primary Cdn distributor for Bergara so I can't say what % of guns in his shop are warranty, but there's a few, and his full timers complain about Bergara warranty processing (but they complainant everything lol), so maybe its true.
With respect to changing brands..well, I'm sure we all have our fans.. my fist Wby was a Vanguard in 30.06 over 35yrs ago... and it shot 1.5 mom when I bought it ( Wby guaranteed that back then) and with handloads I'm getting 1 moa. It could be better with some more load development but its a fiberglass stock w a 20" bbl and honestly? I'm not much of a recoil fan anymore
Keep me posted, I'll check with my boss, although, he still won't accept my challenge between his Bergara and my Wby... he claims eyesight issues in his later years.. which could be..but he's also the one with the shooting trophies... not me
Think he's scared? Lol