This video was posted on Youtube by Hill Country Rifles
As you can see in the video above, 300 yards at a 6 inch target is not a really big deal with the
proper tool, set up and technique. This shooter is using a bipod and rear bag for a rest with a kahles 6-24X 56 scope. Having the glass to not only see what you are shooting at, but to see the middle of the target is the key. Kahles optics are top of the line optics with crystal clear glass and outstanding dependability. Check them out on Amazon here
With my Savage fv equipped with 6-24X50 Vortex scope (only about a $300 scope) I can hit a 21 x 24 inch plate fairly consistently at 400 yards. This plate is about the size of the vitals area of a man. 500 yards is right on the edge of consistency. You can definitely hit further out but beyond 500 yards more luck than skill starts to come in to play at least with this rig.
500 yards is still a very long shot for anyone. Based on the ballistics charts I have looked at, experience, and research I have done, I would say 500 yards with a 22 is like a 308 at around 1500 yards. Many of the same variables come into play. Wind can really play with these little bullets, even up close.
Below is a video posted by Styles622. All shooting is done at 600 yards with an Anschutz 1913 Super Match Target Rifle .22 Caliber Wood Stock using Eley ammo. The target is 3 feet by 3 feet.
These guys were set up really well and the shooter appears to be very competent. Still their shots that impacted were scattered all over the 3 foot target. This is quite a difference from the first video on a 6 inch plate at 300 yards.
So to answer the question, "how far is a 22 lr accurate", I would say it completely depends on the size of the target. On a 6 inch plate the answer is 500 yards. After 400 yards the little round begins to open the group quickly. At 400 yards on a good day with no wind, a 21 X 24 inch plate is doable. With a 3 foot by 3 foot plate it can be done at 600 with the right set up. Beyond that is just poking and hoping.