I've owned a number of Hi Powers since the '60s. I wondered too about a 1954 Hi Power with adjustable sights. I admire you guys who were able to develop cast bullet loads that gave good accuracy. I tried all manner of cast bullets in some of mine. Never did find a cast bullet load that grouped as well as jacketed bullets in my Hi Powers. Tried all kinds of weights, diameters, profiles, etc. No luck. My Hi Powers with BarSto barrels handled cast bullets just fine, but the factory barrels; not so much..
Over a period of 30+ years, I owned three of the GP Comp models. The previous owner of one favored cast bullets, loaded them for the GP, and said it would not shoot. I acquired it anyway. The barrel was leaded up worse than any I'd ever seen. Much elbow grease later, a clean barrel with jacketed bullets shot about as well as any pistol I owned. FWIW, most accurate 9mm bullet I ever used in the Hi Power and others was the old Sierra 115 grain JHC. Don't know if that exact bullet configuration is still available. In factory ammo, the Federal 9BP 115 grain JHP has proven to be excellent as to reliability and accuracy in my guns..