Why do cheap pellets hurt accuracy?

Pellet accuracy depends on tight tolerances on weight, head diameter, skirt diameter, and concentricity.

Cheap pellets are made fast in worn dies, so weights vary by half a grain or more, head sizes vary by hundredths of a millimeter, and skirts have flash and burrs that throw the pellet off-axis. The result is fliers and group sizes 2 to 5 times larger than quality pellets. Brands like JSB, H&N, Air Arms, and RWS are the consensus quality benchmarks.