wolfee said:
Just curious. Anyone ever weigh the charge? Make a guess at what powder it is?
There is a firm selling a .22 rimfire reloading kit, and the writer of this article used it:
https://www.ssusa.org/articles/2018...mallest-223-the-22-winchester-magnum-rimfire/
The kit's maker uses a Lee Loader-type dipper system that has two sizes of scoop, one for each of two types of powder. One powder is 3.0 grains and the other is 2.0 grains, according to the article. The picture with the 3.0 grain powder load in the scale looks a lot like Unique.
Vihtavouri mentions that its 3N37 powder was originally developed for use in .22 rimfire cartridges. A poster on The High Road mentions (without a source) that the .17 HMR uses Lil' Gun. (
https://www.thehighroad.org/index.php?threads/reloading-22-magnum.800064/) And another poster on that thread mentions that he had loaded 2.0 grains of Bullseye in a .22 WMR, and others discuss that they think HS-7 or Longshot is used in the .22 WMR.
I also gathered that while reloading rimfire cartridges is possible, it apparently is a very slow process fraught with a lot of failures to fire and very little load data. Most of the discussion essentially was "well, why not just use a 5.7x28/.22 Hornet/other small-cased centerfire .22 instead?"