Many players also wonder whether bat rolling, bat shaving, or heavy game use will affect a bat’s compression test results during tournament testing. The G4 SSL website includes a video showing a USSSA compression testing session before a Major Men’s slow pitch softball tournament.
A couple things I find odd about the video are that the tester places his hand on the top of the machine while pulling the lever to lock it in place. My research verifies that extra pressure on the top of the machine can change the reading of the gauge by as much as 65 psi. The other issue is the failing of a bat on the first test and it is unusable — there are simply too many variables involved in a single reading. I mention this only because the machines have a +/- 100 psi tolerance when calibrating, but not when testing. The gauge also has a lag when returning to zero. This is a little difficult to explain, but I will try: the needle does not respond instantaneously when moved; it lags slightly and there is some play between the needle and the gauge wheel. This “play” or “lag” can introduce small discrepancies in the reading.)
Even with the machine’s tolerance of +/- 100 psi and the potential for minor human error, compression testers are still a very effective way to keep damaged or overly broken-in bats out of sanctioned play. In some cases bats that show abnormal readings may actually have internal structural damage, which is why professional bat repairs are sometimes necessary to restore a bat that has developed barrel issues or end cap problems.
What compression testing does not do, however, is detect whether a bat has been shaved or rolled.
Tournament directors and league officials sometimes refer to compression testing as a way to “check for shaved bats,” but the machine is not designed for that purpose. A compression tester simply measures how stiff the barrel wall is and assigns a compression number. If the barrel has softened beyond the legal limit, the bat fails. If it remains above the limit, it passes.
That means a bat could be completely legal and still fail if it is heavily broken in, while a modified bat could theoretically pass if its compression number remains above the threshold. The machine is measuring barrel stiffness, not modification history.
For players wanting to understand how bats actually reach their peak performance, it’s helpful to understand processes like bat rolling and how controlled break-in affects composite barrels.
Many players choose a professional bat rolling service to safely accelerate the break-in process and bring a composite bat closer to peak performance without the hundreds of hits it normally takes during gameplay.
On the other hand, illegal modifications such as bat shaving remove internal material from the barrel and can dramatically change how the bat performs and how long it lasts.
Understanding the difference between compression testing, bat break-in, and bat modification helps players, coaches, and tournament officials interpret those numbers correctly and understand what tournament testing actually tells you about a bat.
What Is a Passing Barrel Compression Number?
Compression thresholds vary depending on the sanctioning body and the type of bat being tested.
ASA / USA Slow Pitch
1450 PSI and above is considered passing.
(ASA exceptions to this threshold HERE)
ASA / NCAA Fastpitch
1550 PSI and above is considered passing.
(ASA/NCAA Fastpitch exceptions HERE)
USSSA Slow Pitch
240 or higher is considered passing.
NCAA BBCOR Baseball
Compression standards depend on bat construction:
• Metal bats: 1250 lbs.
• Composite bats: 1000 lbs.
• Non-linear barrels: 800 lbs.
Currently, only a few BBCOR models fall into the non-linear barrel category, including the Rawlings Quatro, Rawlings Quatro Pro, Rawlings Quatro Max, Rawlings Quatro IX, and the Mizuno PWR CRBN.
ASA to USSSA Barrel Compression Conversion Chart
