Hello Tim
Little-John adapter made 2pdr a squeeze gun, similar than German 2.8cm sPzB 41, the conical barrel "squeezed" so called "collars", made from light metal, away around the tungsten core, and so it was possible to achieve very high mv. APCR was the best, but rare, AP ammo for 5cm, it had tungsten core inside light alloy body, it also had high mv but lost its velocity much faster because it was lighter to diameter.
Juha
Little-John adapter made 2pdr a squeeze gun, similar than German 2.8cm sPzB 41, the conical barrel "squeezed" so called "collars", made from light metal, away around the tungsten core, and so it was possible to achieve very high mv. APCR was the best, but rare, AP ammo for 5cm, it had tungsten core inside light alloy body, it also had high mv but lost its velocity much faster because it was lighter to diameter.
Juha