Most springers are limited in the accuracy department by power.

By that I mean, that if you can keep the speed sub-sonic of whatever projectile you are shooting, you will have a much better chance at obtaining longer range accuracy - say - past 20 yards.

Ted, of "Ted's Holdover", has excellent videos on air rifle shooting and has done quite a lot of testing & pest shooting videos.

When watching UK videos, one must keep in mind the FPE limitation of less than 12 fpe they must hunt under.

This makes them pretty much HAVE to take head shots on about all vermin for quick kills, whereas with higher fpe allowances, many body shots are instantly fatal with the extra power.

Here, there is no limit to fpe, however physics gives us the speed of sound for a barrier.

Pellets, that is, waisted pellets that exceed that speed, or engage in the trans-sonoic speed zones, just above of just under, oft times are blood innacurate.

960fps - is a good speed to tune for, with PCP rifles. Just under, as in sub 900fps is good for high quality springers.
Weirhauch is tops, RWS seems second place.

WE tell people who buy the 1,000fps to 1,350fps low priced springers to use the heavies pellets made for their calibre.

In .177. that would be the 10.5gr. Crossman Ultra Magnum, or JSB Heavies and Jumbos that run over 12gr., or H&N or Eungin extra heavy pellets just to get the speed down below the 970fps range.

In "Magnum" .22 cal. an H&H Barracuda 19.01 gr. HP will likely be your most accurate pellet. They shoot amazingly well in both of my High Power .22's.

This outfit, in Richmond BC, had a good supply of pellets and nice rifles as well as air gun scopes. I've dealt with them for a number of years. Kelly is great to deal with.

https://www.dlairgun.com/Air-Rifles/

Another, is Rhonda & Mike at Specialty Shooting Sports in BC. They are closing and have a number of good deals. Good people.

https://www.specialtyshootingsportsoutdoors.com/airguns.html

Another, back East, is Air gun Source.

http://airgunsource.com/

In the States, google Pyramid Air, or?, for your air gun needs. There are others, in both countries & I expect Australia, NZ as well as other countries and continents around the globe.

https://www.pyramydair.com/