I think the not slug shooting crowd have plenty of barrel options in .177 / 4.5 mm, my focus is those that would like to shoot heavier slugs in that caliber, which have 0 options.
Yes Peter / viking airgunner and i live in the same town, use to get my 300 BAR bottle filled by him, he have some luck with 16 grain slugs but for sure not with 20 grain from any of the 3 brands Zan / NSA / H&N
I think the same go for Soren Drost that often shoot another brand from me and peter / VA
I have also put in a lot of work on .177 / 4.5 mm about 4 years or so this far, and i have no idea how many 10.000s of slugs, but i can very easy shoot 1000 in a outing to the range.
The only one i have seen shoot 20 gr well in .177 / 4.5 mm is that South African guy that is on team H&N, and it was so much better compared to my experience that i think either he have a very special barrel or was filming him shooting .22 / 5.5 mm and then just saying it was 20 gr .177 / 4.5 mm.
I can absolutely NOT get any weight H&N slug to fly well out of my maverick, and i think in that brand of slugs alone i have at least shot 800 in each weight class, and tuned for hours on end.
The SA guy used his Impact i, shoot a maverick and Peter too shoot a Impact
I shoot 13 gr very well at 86 M with my maverick + heavy barrel, but i will soon have a 130 M long range, and i dont think i can do groups like that out there, but probably could if i was able to get 16 or 20 gr to work.
At 130 M i would at the very least want to keep my shots on a 2" target none the less.