I have shot and chronied some of there 9mm 124+Pgr and 40sw 155gr+P . The 40 run as advertised in a 4" barrel kahr . The 9mm in a short barrel pistol or not as faster as some other brands I shoot out of 3" and 3 1/2" barrels. But in a 4 1/2" barrel its atleast as fast as advertised.
Got to remember many loads have had there saami specs lowered over time. The 357rem mag is one of the best examplies of having there saami spec and velocities lowered to a lesser level. We have got'n use to the junk produced today that has been detuned from there designed max. That is including the loading manuals. They have to be safe in firearms of lesser quality too.
Some smaller ammo companies just load closer to a cartidges saami limits used today and still load other cartidges to the older standards for those that have firearms design for them as with a 357 "ruger only " loads. Can't say that about the big companies. More about how many rounds they can produce at a lesser or safer power level and do it safely. Atleast try to and we know how that works out sometimes. Some of the +P ammo out there is also a advertising ploy like with the 40sw"+P".
Even some of the 800x loading info has been cut from todays manuals compared to a few years back. Now loads are safer?? And slower