First, you have to understand that a primer flattened by overpressure will fill the groove that surrounds the primer. If you still have a groove around the primer, you're fine.
Second, Federal uses 43 grains under a 168 in their Gold Medal and OTM loads. In a commercial case, that is fine. In a LC case, lower it to 42.5 grains.
Third, and most important, don't be shoving a 168 down to the 2.80 OAL. Your magazine will hold cartridges out to 2.820, take advantage of it.
The middle case below is often mistaken for a flattened primer, but the groove is still present. The case on the right has a primer that is flattened by over pressure.
