Get your barrel cleaned properly, cleaning felts won't do the job as Simon said.
Try some different batches of pellets - the 2016 batches of JSB's all seem to be good, some are extremely good!.
Eliminate as many other factors that might affect accuracy as possible.
You're pretty close to Donny Airgun Range - pop in with your Steyr when I'm around, I've got a VFG cleaning kit and a pull through kit and I can show you how to use them so you can do it yourself. I've also got a few good batches of JSB's that will work well in your Steyr and you can shoot some groups indoors out to 50 yards rested on a bench.
That should give you a pretty good idea of what level of accuracy your Steyr is capable of.
I doubt very much it's the crown, unless the previous owner has been dicking with it.