There are a couple Walther springers - one anyway and it's deemed to be decent rifle with good accuracy, at least in the sub 500fps range.

Tony Wall of Sandwell Field Sports in the UK is a master at tuning air rifles.

I inquired about sending one of my HW's to him and he said he could receive it and tune it, but was not legal for him to return it to me. lol. Bloody laws.

https://www.youtube.com/watch?v=Twg7e2jdAs0