I think you are completly right however if we talk about reliable semi auto rifles today we have rifles for the original military cartridges in mind. there can be no doubt that a lot of money was used since WW 2 to make such auto rifles so reliable as we find it now.
but this is about big bore ARs and they use cartridges the action was not build arround. this cartridges are sometimes semi wildcats and handloading only rounds and I dont believe they working smooth as the original caliber in such automatic rifles.