I sympathize with you in your frustration.
There is one other thing I can think of that might hold some potential for a solution---headspace. I am not familiar with the Anschutz 54, but I had a 541-T that had just a bit of excess headspace. The bolt in the 541/581 is two-piece and I was able to assemble it with a shim in between the two parts to decrease headspace a bit, and it seemed to help.
I have also done a bit of rim thickness sorting with some rimfire ammo. I used a Stoney Point bullet comparator set with the .24-caliber insert and used this to measure. It may not give good absolute measurements, but I think it's an effective technique for sorting. Measurements seem to range from 0.040" to 0.043" and you might gain some insight by sorting and shooting the stuff with the thickest rims and comparing to accuracy of ammo with the thinnest rims. That's no solution to the problem, but like I said, you might gain a little insight that could help you determine what the problem may be and then correct it.
I had to drill out a little material in the comparator body to accommodate the length of a .22 LR round.
Best of luck...and please let us know what the problem turns out to be---I hope you figure it out!
