This is from the senior site:RE: SSUSA Bat Performance Standard
Terry Hennessy of Senior Softball-USA has asked me to document a change in the SSUSA bat performance standard. This original SSUSA standard was the ASTM Standard F1890-05, with 47/375 softballs. Because these softballs were not readily available, the test softball characteristics were changed in 2007 to 47/525. The increase in BPF that this change brought about was, however, not incorporated into the BPF limit, which remained at 1.20. As a consequence, softball bats that were initially compliant could become non-compliant.
To avoid this possibility, SSUSA has decided to increase their BPF limit to 1.21. Specifically, the new SSUSA standard requires that the softballs used in the tests have compressions in the 475 - 525 lb range and CORs in the .460 - .470 range. The 47/525 balls are readily available and have been used for the past seven years in performance tests for SSUSA, USSSA, NSA, and most other softball organizations. Also, the higher compression softballs are more suitable for bat testing because their compression measurements are much more stable (repeated compression measurements give similar results) and consistent (compression measurements at different points on the balls give similar results). This BPF limit change does not permit more-powerful bats to become compliant (as long as 47/375, or weaker, softballs are used in the ballgames). It has simply adjusted the limit to account for the increase in test ball compression.
Using the 47/525 softballs, the current 1.21 SSUSA Standard differs from the 1.20 USSSA Standard in the following ways.
1. The bats are tested only at the COP for SSUSA, and not at other points along the bat barrel. The maximum possible bat performance might therefore be missed.
2. The BPF 1s evaluated to only two decimal places for SSUSA. This means that BPFs as high as 1.214 (ABPFs as high as 1.264) are allowed. For USSSA, the maximum allowed BPF is 1.200.
3. Only new bats are tested for SSUSA. Possible performance improvements with usage will therefore not be detected.