Personally, I doubt the logic of trying to emulate .22LR performance with anything but a .22LR . It sounds to me like trying to retard the swing of a sledge when dispatching ants.
Use the real thing.
This
http://www.budsgunshop.com/catalog/product_info.php/products_id/22100 is my recommendation for an affordable means to bring .22LR performance onto a target within .22LR range.
..And yes, I have tried the Unique with .223 and .22-250 solution. Total waste of time, especially when the winds blows, which is pretty much always...
Coincidentally, it is also a pretty good solution to providing subsonic performance at about the same distances.
Honestly, I think it's a no-brainer.
'Nuff said.
Greg