I put a stainless .22 Magnum barrel on my 77-22 and have found it not as accurate as the best .22 LR loads, but still as accurate as I could ask for. I did also have to change out the trigger guard group and do a little whittling on the stock, but it has not had any negative effects on accuracy. It is possible to modify the 77-22 from LR to Magnum, but not the reverse, due to the spacing of the firing pin. I am not in love with the trigger of the 77-22 since I put an aftermarket trigger on my 10-22. Until then, I thought the 77-22 trigger was all right. What I have noticed about the more expensive rifles is that they shoot all ammo well, though they do show preferences, but the differences are much less than for cheaper guns (YGMMV).
I got the barrel from another GBO member at a very reasonable price. If you were to go this route, with two barrels, another trigger guard group, and a .22 WMR magazine, you could have a .22 LR, a .22 WMR, and, a .17 HMR. Not a bad rimfire battery, if you ask me.
Put me down for a Ruger 77-22.