I too would discourage the use of 22rf ammunition marked HV in the older firearm(s),,seems just natural.

....But I have a question if any of the scientist types out there can answer for me...

When you look at the SAAMI specs for RF ammunition:
http://www.saami.org/specifications_...MI_Rimfire.pdf
Scroll down to page 6 of the pdf for the chart.....

All the 22LR is grouped together. The only way to sort them out is by bullet style, weight and velocity differences.
From that chart you can easily see the Standard Vel ammo in the mix among the various HV loads.

But,,all the loads regardless of velocity (standard vel & HV) are rated at the same Max Average Pressure of 24,000psi.

Further down the chart is listed 'Match Ammunition', both Rifle and Pistol. Obviously Standard Vel stuff at 1100 and 1135fps (the pistol ammo is faster?).
But again the Max Average Pressure is the same as a Stinger 22LR at 24,000psi.

Even the lowly 22Long in it's very own catagory is rated at the same pressure.

So why are Standard Vel 22LR's considered lower pressure ammo when the industry standards allow them to be loaded to the same maximum pressure as any other High/Hyper Vel 22 L/R ammo.

Lower Velocity but not necessarily lower chamber pressure,,or what is my completely non scientific mind not seeing?