"AMT's manufacturing of the 'Lightning' pistol and the 10/22 rifle was not in violation of any patent but Bill Ruger did not like the situation so he sued. The suit was settled and in return for no longer manufacturing and marketing the AMT Lightning pistol Ruger would not object to AMT stainless steel copies of the 10/22."
This quote came from the co-owner of the AMT Custom Shop.
He also told me that there were 2 versions of the AMT rifle, the 25/22 and the Target!
Also he told me that they actually bought bolts for the Custom Shop 'Challenge Edition' rifles directly from Ruger and he stated "believe it or not we actually had a pretty good relationship with them"!
I owned an AMT Hardballer in .45 and the rifling/bore looked like it was done with a dull drill bit. Unbelievable it shot as good as it did. Same dude musta rifled the Lightning barrels
HTH
Respectfully,
Dennis