I was told that a well known company is working on mags for the 10/22 .22 magnum and a separate one for the .17 HMR -- 25 round mags! They are in developement right now! I don't know the time table for availability.
A number of us sent messages to Butler Creek asking about high caps for the magnum. We all received the reply that it would be forwarded to R&D. Then later, some one (not BC) posted about the cost of making molds for plastic mag production and how the cost was too high if there wasn't enough demand. But I guess you never know, some one could be doing it. The 10/22 magnum has some following. I'd buy a couple for mine, at least if they were Butler Creek manufactured. :t