Steve at the Firearm Blog posits a question from a reader about 60 grain .22 LR ammo, the only loading of which I’m aware of is the Aguila SniperSubSonic load. I’ve actually done a lot of shooting with this load through various platforms, and while it’s a neat idea it’s not really practical when compared to standard .22 LR ammo. The biggest problem with the 60 grain stuff is that you need a special barrel for it – the twist rate to stabilize the heavy and long 60 grain rounds need to be 1:9 as opposed to the slower twist in most .22 LR barrels.
Another problem that you run in to with the Aguila when shooting it from a Ruger 10/22 is the bolt opening prematurely. The round is so heavy that when you fire it, unless you have a heavy charging handle made out of tungsten to add some weight to the bolt, it can open before the powder is finished burning, creating a disconcerting “flintlock” effect from the chamber of the rifle.
I like the Aguila stuff, and shot it extensively out of my Walther P22 for a while, as for whatever reason the P22 really liked it. That being said, it’s sadly confined to “novelty” and “niche” markets because of the amount of modification that you have to do to a factory rifle to get it to run right. Plus, it costs more than regular .22 LR ammo, so if you’ve really got your heart set on overpaying for rimfire ammo, just buy a .22 Magnum instead.