I, too, have wondered about the safety of using a hot .40 load from vendors such as BB, DT, Underwood (I know about the chrono results folks have seen from DT).
BB states on their website that Glock OEM barrels are not to be used with their ammo. DT posts results using Glocks, Underwood doesn't say. Are the +p designations from some manufacturers a true indication of pressures that exceed SAAMI specs, or are they a marketing strategy?
It has been my practice to stay away from .40 "+p" loadings.