Just thought I'd add to this thread with my own experiences here - CA Mesa 7mm rem mag. The first 'nice' rifle I've owned.
I'm and east coaster and started hunting out west last year. I didn't have a rifle capable for western big game (I have a Savage Model 110 pre-accu trigger chambered in .243 - I love that rifle, absolute tack driver, and has taken down a ton of deer over the years, but couldn't cut the cake for this trip). Long story short, I was told by a buddy who lives in the area we hunted to save my money and borrow his rifle, but it fell through so I had to share a rifle and be second in line with my tag. My wife took pity on me and bought me a CA Mesa 7mm rem mag for Christmas last year, my FIL gifted me a Gen 2 Viper PST to go with it.
I also followed the CA break in process to a tee. but I have not been able to get the rifle to group sub MOA at 100 yards. I have put Remington Core-Lokts, Federal ELD-X, Hornady Precision Hunter ELD-X, Hornady Super Performance SST, and some cheap Sellier and Bellot down the barrel. The only round it kind of consistently shoots a group with is the S&B, but even then it isn't sub-MOA and I will occasionally get some real fliers (over 3-inches outside of the group). At first I thought it was me, then I shot my .243, that grouped sub-MOA as per usual. I moved on to making sure the scope rings were secure. They are torqued to spec. Muzzle break is tight. I have ~130 rounds through the barrel. Group size varies widely, the best I've gotten the rifle to do is about 1.5MOA @ 100 yds. It sits about 2.67MOA @ 100 yards, but the entire spread is large - enough to make me hesitant to take it out next weekend for whitetail rifle opener.
Today my friend and I hit the ranged to test out his new suppressor for his Tikka 3x Lite .270. He shot sub-MOA groups at 100yds. Then I had him shoot my rifle, and again could not get a good group. He then went back to his rifle and shot sub-MOA groups. I shot on his rifle and again, sub-MOA groups.
The FFL the rifle was ordered through is also a seasoned gun smith (over 40 years). He is aware of the issue and suggested after checking scope mountings to call CA. Will update as this progresses, but just throught I'd add my experience in here for reference.