I wonder if the OP picked up a .20 cal or not.
I have always sworn that I wouldn’t buy anything but .177 and .22. Lo and behold when I had the chance to get my hands on a Crow magnum I didn’t care what caliber it was. You guessed it a .20 cal . So I had no choice but to get some pellets. I ended up stocking up on the 13.73 JSB’s as they were the best price. Lucky as they shoot great from the CM. Fast forward a month or so later and an absolute steal of a deal on an HW100 came up only it was in .22. I have since converted it to .20 . I have a few finishing touches to do in the .20 HW100 before I can claim whether it likes the pellets or not.
So far I’m liking the .20 cal , rather flat shooting in the 820 -880 FPS range.