In November 2023 the USBC ruled string pins score no different from free-fall machines. The same nineteen-page report recorded fewer strikes, a narrower pocket, and worse pin action.
The United States Bowling Congress spent three years studying string pinsetters. Its own lab robot — EARL, the Enhanced Automated Robotic Launcher — found a measurable scoring gap: a 6.9% drop in strikes in the 2020 phase, then 7.1% fewer strikes and up to 10 pins lower per game in the April 2023 report. That report made string pin bowling a separate category, with averages NOT interchangeable with free-fall.
Then the methodology changed. Instead of the robot, the USBC ran 350 human bowlers through four games each — a test it designed to detect a gap of four pins or larger. It found “no statistically significant difference,” and executive director Chad Murphy changed the playing rules the same day the report was published, “in collaboration with the industry’s manufacturers.”
The Professional Bowlers Association followed. It tested and approved exactly one machine — the Kubica AMF Edge string pinsetter. Within a year, Kubica AMF was the PBA’s presenting sponsor, with EJ Tackett and Jason Belmonte bowling its machines at the 2025 PBA All-Star Weekend.