Had the same issue with my 300 wm terrain. I found it was a Really rough chamber when I called bergara they confirmed. Fixed it myself but they offered to fix it about an 8 wk turn around.
Bought a b14 WT fires 160 rnds before I figured out that the muzzle brake only had .008 clearance they spec is .030 min. If you wish to still reach out to bergara I have the service manager contact info. He took very good care of me the muzzle brake correction fixed my issue.
Just got done shooting today with a 6 yr old his dad took all the spacers out of his bergara hmr, it fit him like a glove. We put it in a bog death grip and had him ring steel out to 600 about 500 further than he will be shooting😁
I know of at least one of the bigger online resources is only putting powder on their retail shelves and not listing it online. Checking with your local shops is the best way I’ve found. Alliant powders and H-1000 have been showing up locally over the last few months.
I have 1-10 twist shooting the 200 gr eld-x. I don’t have data in front of me but H1000 2889fps 26 inch bergara. If I remember correctly is was a very narrow node. Under .5 moa