Prior to converting my 10/22M (.22 mag) to .17HMR, I haven't really had any problems with the gun function wise.
When I converted, I did get quite a few stovepipes in the first 100 rounds but attributed it to a still relatively new gun (noe more than 200 rounds of .22 mag fired through it previously). I also encountered rounds hanging up in the stock mag I was using. I had talked to a fellow shooter a couple of weeks before and he mentioned and showed me the same hang-ups with his 77/22 mags (same mag as the 10/22M). What I found as the cause for the problem was the mag bolt torqued just a bit too tight and so the interior length of the mag was justa tad tight for the overall length of the .17 binding the rounds inside. I loosened the mag about 1/8 turn of a hex wrench and everything went fine from there on. (Actually loosened a bit too much the first time around and the mag got stuck in the mag well. Had to disassemblt the gun to get it out. No biggy, the 10/22 is easy to take down.)
Bought 4 assitional mags from CDNN and they have worked fine out of the blisterpack without mods.
My regular 10/22s (.22 lr) have worked fine. The only ammo that doesn't work in any of the ones I've convereted with bull barrels is Rem Thunderbolt. Those things only chamber in the stock barrel which aren't as tight as the aftermarket barrels.