What setting do you have for torquing the action screws. Try loosing off the action screws retorque starting at 25 in/lbs. fire 3-5 5 shot groups. Increase the torque by 2 in/lbs repeat and so on until you hit a MAX of 35 in/lbs, pick the best group of the test . The Anschutz 54 action is only rated to a max of 35 in/lbs for the action screws. Try different ammo. I have the 1712 it likes SK match and long range, Lapua midis plus. The mag you will have to tinker with. The ejection of spent round you can fix by very light file of the outer extractor. See Rimfire central they have a how to do on their site.
Regards George
Regards George