bolt not locking back on last shot

[Shivesy]

In my opinion you accomplished nothing by adding a adjustable gas block and running it wide open. Would that not be the same as just a basic gas block? Adjustable gas block wide open and a basic gas block is going to flow the same amount of gas, whatever the gas port will allow. How far are your spent cartridges landing? I would quess 3'-4' would be common. Are they flying that far? I understand using a adjustable gas block if your over gassed because then you can tone down you gas flow. Some folks I have talked to open up their gas port a little larger than needed then tone it down as needed via an adjustable gas block. I don't really agree with that method but that is a different way to monitor gas flow.
As far as the dented cases. I was under the impression that it was a common issue. I run the soft piece of velcro on the deflector and now no more dented cases. Do you know your gas port size? Just a thought but you might want to open up your port hole just a tad more and if that don't do it then tone your gas back down with the adj. block. I also helped a friend with a situation like yours that was not gas related. The vendor sold him a longer buffer spring than what he needed. He had a collapsable stock and they sold him a fixed butt stock spring. We cut the spring down as a quick fix and his rifle cycled properly. Good luck and I hope you get it figured out.