I have been shooting Steyr rifles since I started in 2005. Fantastic bit of kit all variants.
Ernst Huber at Steyr advised me NOT to lube pellets, so guess what. Yes I tried lubing them with a famous red liquid. Results were not good.
Nowadays I listen to people that know and run my Steyrs DRY.
I also had some of the very first JSB Expresses in the UK via Harry Preston and was told by Pavel Kolebac of JSB that they were the same as Webley Mosquitoes. Originally because of the exclusivity deal with Webley, you could not buy JSB Express in the UK.
I used both pellets from the same pouch without turning a hair.
Why don't you try a tin of 4.52 Express running at around 810 fps DRY and see what results you achieve.
If you have a barley twist then you shouldn't have too many problems with "fussy barrel"
Hope this helps