The m2 brass can definitely be reloaded. I have reloaded thousands of those cases.
Most deprime pins were not up to the task of depriming the crimped-in primers. I sold it years ago, but I had a manual deprimer that consisted of a base and a deprime rod which was inserted and tapped with a hammer to remove the primer. I believe mine was made by CH.

There were, and I suppose still are, primer pocket swagers. This tool was driven into the pocket in order to properly size it for a new boxer primer. There were also primer pocket reamers which were used to remove the crimp. They worked similarly to a manual shell trimmer.

One thing I noticed was that some lots of ammo had very light primer crimps and could be deprimed with an ordinary resize/deprime die. These also could be reprimed with no reworking of the primer pocket.