I found plenty of designs and purchase options for .22LR/.17HM2 single shot adapters (sleds) but nothing that would work for .17HMR. I took my original Anschutz Model 1517 (mod. 64 action) magazine and measured it, putting together my own version in Tinkercad. After 11 different versions and tweaks, this is the result. This will replace the magazine entirely, utilizing the original magazine catch.
After printing, I recommend doing some minor sanding to the portion the cartridge slides on, though it will work without sanding.
Anschutz64_17HMR_Sled.stl | 67.1KB |