Hi Matt....once the earlier models had been sussed for the POI shifts due to the barrel screw, it doesn't really happen much to Steyrs these days, at least not on the few hundred i've looked at in the past few years
. Of course it's plausable that you have the Friday afternoon Lemon but i doubt it and suspect that it's something simple like barrel cleaning or the wrong pellets. Is it a long barrel version?
Just for info...and this is by no means a definate for fault finding
POI change that looks like 2 groups slightly apart (high/low) from each other that eventually make a single large group the more pellets you fire....reg creep (not settling back into the correct pressure after each shot or bleeding air through the o rings/piston that causes the reg pressure to creep upwards.
Dropped shots....hammer dirty, hammer spring, firing valve/spring o ring wear.
Flyers at the 12 o clock/1 o clock position....dirty/knackered barrel or wrong pellets
Poor grouping in all positions can be the hammer spring, i've fixed this problem before despite common sense saying that the hammer spring wouldn't cause this. Quite a few grouping problems are just down to the barrel cleaning regime and the batch/make of pellets.
Air rifles.....go figure
If you lived closer mate i would have a look for you but Rich Woods is handy with Steyrs so maybe have a chat with him?. If you can hang on until the UKAHFT round at Quarry i have a spare reg you can put on and try.