Started resizing several hundred cases of various brands of 308 and noticed that the PMP cases appear to use small rifle primers. Is this correct? I could buy a 100 small rifle primers and reload them. Is it worth it? I think I may have 40 or more cases. Is the PMP brass worth using?

Many will use the 308 b rass with the small primer as is and resize to BR becasue they feel the small primer gives more uniform ignition. For only 40 cases I would not jack with it sell it and replace with cheaper large primer brass.

Check the primer pockets to see if there showing signs of a crimp. IIRC a lot of PMP brass has crimped primers (IOW run it over a pocket swadger or try cutting a slight bevel with your case mouth chamfer tool)

What kind of reloading are you doing? When I was shooting a 6.5-08 target rifle, I used the small primer brass to load the ammunition I shot at 600 yards because the accuracy was better. With hunting ammunition you probably would not notice any difference.