In a lot of instances a cheap shell will run at a much higher pressure to achieve the same velocity than a much more expensive round that was designed for fine game guns. Cheap shells are expected to make every type of shotgun work without a burp and catch flack if they cause problems in the finickiest auto. Nobody expect RST's, Gamebore or Vintagers to run in a 3.5" semi auto.

After the first shot the rest are just noise.