this is an interesting article and I learned some stuff I didn't know about making rimfire ammo. It's intriguing that they haven't perfected the recipe for rimfire primer compound...and it has ground glass in it...which the bench rest guys aren't thrilled about.

Another interesting thing is that earlier target rimfire ammo seems to be easier on barrels than current varieties. I haven't seen why yet. Anyone know?

https://www.americanrifleman.org/articles/2010/9/10/the-impossible-22-rimfire/

It's common knowledge that Eley Tenex is incredible...Olympic quality. This is a cool article about it and how they have greatly improved the priming system called Eleyprime System (EPS).

http://www.shootingtimes.com/ammo/ammunition_eley_101405/#ixzz2j9WiPxwH

.22LR's lately. They are more available than HiVel and cost less, too (but still not cheap).

One thing I have noticed is that the StdVel cartridges burn more dirty than HiVel ones. This is with two different brands of StdVel cartridges vs a half-dozen types of HiVel. The first patch through the bore is much darker for StdVel and it takes 2 or 3 more patches to completely clean the gun. Cannot tell any difference in practical accuracy, though.