The carbine was never meant to be a front-line combat rifle. The original idea was to was to develop a light rifle that was more effective (more accurate, greater magazine capacity) than a pistol that could be carried by support and rear-area troops.
Although once in the field it ended up up being issued to many other troops in all conditions.
Reports from Korea were particularly critical of the carbine where it performed poorly in the cold weather and was in many cases ineffective against the heavy winter clothing worn by the Chinese troops.
It was criticized again in Viet Nam where it was issued in large numbers to ARVN troops and was found to be ineffective in jungle conditions where the .30 round was incapable of penetrating the dense undergrowth.
However, it was probably "handier" in those same conditions than the much longer and heavier M14 that was the standard rifle until it was eventually replaced by the M16.
Although in hindsight it wasn't a great combat weapon, its small size, mild recoil, and magazine capacity are exactly what make the M1 Carbine a great "plinker" and a fun rifle to shoot now!
And Vlim, that's a great box of ammo! I've only ever seen pictures of them in books.