[amamnn]

The same Q was asked in a back issue of one of the gun rags I have subscribed to in the past. The answer was that back in the days when men were men and rimfire silhouette shooting was a new idea (in the US at any rate) an intrepid group of rimfire pioneers began pulling bullets from commercial .22 lr rounds and substituting 60 grain bullets with the smaller rimfire pressure ring into the open cases. The the alleged reason behind the operation was that 40 gr. .22lr bullets would not reliably knock over the 100meter rams. You can believe it or not as you choose. I don't remember which gun rag it was and I'm not going to search 35 year's worth of back issues.

In re. the 17 HMR:


"A LITTLE .17 RIMFIRE HISTORY
Development of the ammunition has been a long process. If you're a longtime reader of Shooting Times, you may already be experiencing deja-vu. If you've kept your back issues, take a look at the January 1992 issue for an article called the "Revolutionary .17 Rimfire." In that article I outlined experiments by Steve Chernicky, Terry Kopp, W.A. Eichelberger, A.J. Jones, Fred Wood, and others who have worked on various versions of small caliber rimfires. Shooting Times technical staff member Kopp's round was called the .17 KRM. It fired a 25-grain bullet at 2100 to 2400 fps that was intended to duplicate the performance of the defunct 5mm Remington Magnum. It did so nicely--and then some. Chernicky, on the other hand, went all out for velocity, pushing the limit and eventually getting 2700 fps with lighter 20-grain bullets.



Chernicky had so worked out things to the point that everything went smoothly. The actions had first-class rebarrelings, and the handloads were carefully assembled to .01 grain of powder. With velocity results like that a whole lot of people in the industry were excited about the prospects. I figured it was just a matter of finalizing R&D before we saw ammunition from a major company."