This has been on my mind for a few days.

In the world of spring rifle tuning, we now know, to put it too simply, that the route to higher power is through greater sewpt volume, longer stroke, and efficient flow dynamics through the transfer port. Just bunging in a bigger/stiffer/Ox spring increases recoil much more than power (which sometimes even goes down).

Still with me?

Now, transfer that to classic Webley pistols.

The Senior has slightly greater stroke and therefore swept volume than the Mk1. And makes more power.

But the Premier has slightly longer stroke than the Senior. But is not as powerful.

And the Hurricane/Tempest appears to have about the same swept volume as the others, but is potentially much more powerful.

Chris Thrale's book lists the .22" varities at:

Mk1: 273/293 (NM)
Senior: 330
Premier: 310
Hurricane/Tempest: 330 - but "with proper lubrication and adjustment" 410, and chrono-tested at 400 in US spec with a different spring.

Can you really get a 25% power increase in a spring pistol basically by shoving a more powerful spring in?