Power factor is the weight of the bullet times the velocity divided by 1,000.
So, the PF of 150 for Minor scoring can be the 55 grain .223 bullet at 2,700 f/s. if I calculated correctly.
Or any other combination of bullet and velocity that yields the PF of 150.
Anything .223 or larger is ok.
Ditto for figuring the PF of 320, for Major scoring.
Major scores more generously than Minor, as a reward for shooting a more effective caliber.
Same for pistols.
The rule books explain it all.
In the US, except for sanctioned IPSC matches, USPSA rules apply, similar but different in regard to targets and gun catagories.
You can read them, too, at uspsa.org.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”