Very interesting.First of all, it's my understanding that +P+ is not a SAAMI sanctioned load. That means no one has defined it. We all know what we
hope it means, but that's not always the case.
• If +P means higher pressure, I sure hope +P+ means higher velocity without yet again higher pressure. I'm not sure most guns could take much more chamber pressure than +P.
• In standard "classic" loading we consider chamber pressure and bullet velocity to be linked 1:1. This is why and how a chrono is useful in reloading. But that doesn't always hold true. Somewhere north of Max Load, those 2 features separate and become independent. Velocity levels off and goes asymptotic. On the other hand... Pressure continues to climb like a rocket. This is one reason guns blow-up.
But pros, like Federal, can use proprietary blended powders and other methods not available to reloaders because they have millions of research dollars to spend looking and testing.
So the bottom line is I'm not sure +P+ buys you anything. It's undefined. You could be spending $1.50 per round, and it could be standard ammo in drag. Federal could be laughing all the way to the bank ! Or it could be 1300 fps at standard chamber pressures. The only way to know is to read the box or web page, and look at the specs.
If it was a no-name ammo company on YouTube, I'd write it off as another
flash in the pan rip-off. But Federal is one of, if not
the, top ammo maker. Hard to say.