The USBC tested string pins on 10,658 real league bowlers — its own report found scores came in LOWER (−6.9 at the top). Then it buried the result.
In November 2023 the United States Bowling Congress ruled that scores on certified string pinsetters needed no adjustment, and league averages on string and free-fall machines became “interchangeable.” The PBA leaned on that finding when it cleared the QubicaAMF Edge String for competition in November 2024. The whole structure rests on one sentence: string pins and free-fall pins score the same.
Twelve months later the USBC ran the largest real-world test of that finding it had ever attempted — paired before-and-after league averages for 10,658 bowlers across 66 centers that had already converted. The String Pinsetter Scoring Report 2025 found a mean of 3.4 pins lower on string pins, a near-perfectly linear drop the better you bowl (R² = 0.90), and 6.9 pins lower for bowlers averaging 210+ — about two fewer strikes per three-game set. In the USBC’s own words, the impact on higher-level bowlers was “outside of what our original research suggested, but aligns with pro bowler descriptions.” The pros were right.