I once heavily sprayed two attacking dogs with the mailman pepper spray. They didn’t even slow down. They didn’t notice it at all. AFTER, they were quite red and irritated, and rubbing themselves, but that’s not the point. If it had been me they had been attacking, I would have been in trouble.
Now, I’m not sure of the difference between the PO issued mailman spray and any other.
A friend's sister was walking along a Forest Service road here and unexpectedly came upon a young bear. Without thinking she immediately brought up the bearspray can she was carrying and gave it a strong stream right into its face, whereupon the animal bolted from the road and up the hill as fast as it could go, bawling all the way. I did not personally see it happen, but that is how it was relayed to Me so at the very least I would spend some personal funds and buy some of the good stuff from one of the bigger Outdoor, Sporting, Hunting and Fishing stores that one of the experienced outdoors-types recommends.
The only Government Standard Issue item I have ever trusted was the M1911. Anything else I always customized and tweaked as much as possible for instant and flawless operation.