MN22lrFan,
I'd love to see your 547! Can you point me to a thread that has pics of it or post one here? I regret passing up a 40x made into a .22WMR years ago.
The .22WMR ammo with the most consistent accuracy I have every shot has been a couple of old lots of Winchester 34gr Supremes. The majority of my WMR's have shot it better than other ammos I've tried. My Marlins all preferred 40gr JHP's. The next best has been Remington 33gr's and Hornady 30gr VMax's, followed just a little by a newer lot of Winchester 34gr Supremes from a few years back. I don't do 10 groups of 5 though. I only do 5 groups of 5 when selecting ammo for my WMR's, usually with a 36x scope, and then switch to a hunting scope.
My most accurate WMR Rifles right now are my Biathlon Basic and my 77/17 with octagon GM WMR barrel. The BB has shot almost everything I fed it well. So far, at 50, the Ruger has out shot the Annie 1720 DHB I used to have...I forget what ammo the Annie liked (I think the Rem. 33's), but it shot consistently around an inch with occassional groups closer to .5 at a 100yds...it would shoot right along with my Cooper .17hmr, but could not keep up with my Annie 1717HB. But, it's early and I've only shot the Ruger at 50yds, so much too early to say anything for sure. It was shooting the old lot Supremes in the .2 and .3's when I was shooting it, with one group just over .5 that had a flyer low and left...I am thrilled with the Ruger, pretty and accurate enough for my purposes.
My next most accurate WMR is a CZ512 right now. It's the most fun one I have too. It's shooting old lot Win. Supremes at .5-.6 at 50, and newer lot Supremes in .6's to sub-.8's at 50yds. At 100, it shoots groups in the 1-1.5" range with old lot Supremes and occasional sub-1". I haven't tried the Hornady 30gr's yet, but look forward to trying them in the CZ.
My 9422M gives the CZ a run for its money, but the Winchester is harder to hold steady from a bench with the skinny forearm. Years ago I mounted an 8-32x scope on it and, with old lot Supremes got occassional .75" at 75yds and almost as good with old lot Win. 40grJHP's, but the JHP's had more flyers. The accuracy potential is there, but I just can't hold it as consistently as I can the other rifles.
I'm a hunter not a target shooter, so I don't know a lot about the details of the ammo, etc.