22 rimfire ammo
One needs a smooth rimfire barrel to begin with. Fire lapping a rough barrel and/or cryogenically treating it may smooth it up. Once you have a smooth barrel that doesn't foul too badly then most anything will shoot in it. For target off-the-bench work at paper the SK Jagd fodder from Germany sold through Champions Choice is the best deal around. Their cheep Standard Plus will average half-inch groups even beyond 50 meters/yards. SK Match and Rifle Match will drive tacks out to 100 meters and their Match Gold (big bucks stuff) will simply out perform anything that I've shot in the past 40 years. Last years NRA Smallbore Rifle Silhouette National Champion, if I'm not mistaken, shot the SK Standard Plus and fired a score of 38 of 40 in the winds at Raton, NM. That should tell you something about the off-hand accuracy of this stuff.
For a bit more power to put over those IHMSA Field Pistol and NRA Hunters Pistol steel targets, I like the faster copper plated fodder. PMC High Velocity 38 or 40 grain and CCI's newest 40 grain Velociter is right for me in a ten inch TC Contender barrel.
For the 22WMR rimfire one cannot go wrong with either Winchester HP's or solids for accuracy in most pistols or/and rifles. PMC is right there also. CCI's 50 grain Gold Dots are slow but they sure put the steel targets over with more authority. If you need more power with the 22WMR then it becomes expensive but worth the effort if you do, just put a 25ACP shell holder in an old C-press, use a Hornady press type bullet puller in the C-press and pull out the factory bullets using the same safety rules as for reloading. Seat some good 50 to 52 grain .224 bullets over the factory powder that came with their 40 grain loads. Just make sure that you don't compress the powder when you seat the bullets, and only shoot these reloads in temperatures of 75 degrees or cooler temps because of possible pressure problems of sticky cases or blown out rims.
What else is out there?