Interesting that you bring this up regarding the 15-22.
I shoot bullseye in a couple of leagues and this topic is frequently discussed.
Most of us use the CCI Standard velocity, finding it reliable and consistant and economical, except for this excessive wax buildup problem.
Those of us using S&W 41s find that other than actually wiping off each round on a rag as the mags are loaded, it was found that dropping a drop of oil on the nose of the last round in your mag seems to prevent misfeeds & jams, but you still need to clean the chamber frequently to get the wax buildup out.
The magazines also get a lump of wax inside the front edge, about 1/4" down from the lip. You can depress the follower and scrape this out with a dry rod and continue shooting.
Those that use Rugers, find there is no tolerance for the wax, the mag front to back length seems to be less than an S&W mag, they lock up too often and invariably they find some other ammo.