What is the fine-grained topic of the following text: The SX4 Waterfowl Hunter Semi-Auto Shotgun uses the proven Invector-Plus™ interchangeable choke tube system that works hand-in-hand with the back-bored barrel to reduce shot deformation and promote the uniform shot patterns you need to wallop birds at long range. Only return the topic.
SX4 Waterfowl Hunter Semi-Auto Shotgun features and performance