Hi - I just got a B22 FV last week and have run about 150 rounds thru. After a thorough cleaning I started with 48 rounds of Herters 36g HP-HV bulk .22 for 'break-in', then switched to Federal Champion 40g RNL. The H was variable as expected, about 1-1/2 " groups, then I swabbed a couple patches then ran the Fed. I only ran 26 rounds 'cause the wind got up to around 15 mph, but my last group was 0.565" at 50 yards. Good enough for the first day!
While cleaning before going out, I 'fixed' the cocking pin slot issue, and also broke the edge of the bolt handle slot as it was sharp too. I found the mag a bit awkward (never had a 10/22) but got used to it. However, the lower left side of the bullet slot had a 'pointy corner' that needed to be smoothed. my thumb got several scratches from it.
I also found that if the mag is inserted while the bolt is Open, the mag goes in easier. Closed bolt is 'iffy' for the mag, but that may change after a few more hundred rounds?
Overall I would have given the rating about 4.5 due to the issues I mentioned, especially since they have been documented since the gun came out in 2017!

BTW - Who has experience with the butler creek 25-round mags? They are listed as only for the A22, but I've seen some comments that they are usable in the Bs too. Anyone here done that ?? And here in Canada I can't find any of the 10-round mags - is that 'cause they're popular or just limited stock ??