MagPro is a run of double base ball powder manufactured at the former Olin St Marks plant in Florida. It is the reason that Hodgdon developed the "Extreme" line of powder at the Australian Defense Industries facility in Australia (French ownership).
MagPro is amongst the most temperature sensitive powders available. The US military uses similar ball powders (close to Win 748 and 760 in handloader form) from St Marks but not for accurate sniper ammunition. I have a friend, a retired Physics professor, who tested small arms and ammunition for the US Army Aberdeen Proving Ground (Nome in the Winter followed by the Panama Canal Zone) and they chose Reloader 15 which is a Bufors stick powder made in Sweden because of its temperature tolerance.
MagPro is my favorite powder because of the velocity it produces with 140 Accubond or Berger Hunting VLDs in .270 WSM. For some reason MagPro disappoints in the 6.5 WSM for which I have two rifles. In the 6.5 WSM it produces less velocity than Retumbo and VV N570 using 130 and 140 gr bullets.