I bought one of those P10 Grendels when a company representative showed up at my department to show them, and several of us bought in on an agency PO. It has always worked reliably (with ball ammo; never tried anything else) for at least the first full magazine, which is all you would have in a fight. After the second, it crudded up quickly (mine was very tightly-fit) and started malfunctioning.
Most people, we cops included, didn't get the full point behind its design, and we frequently mocked it ("so, when it's empty, we throw it at 'em?") What people failed to see is that the gun was marketed to those who would normally be carrying a 5-shot .38 snub, especially the many of those who rarely carried a reload for it. Kelgren was trying to offer, particularly to cops who sported a 5S38S on an ankle as a BUG, an option that was lighter, thinner, shot just as simply, and had no external controls (magazine release, safety lever) that could be inadvertently actuated during the rigors of carry. On top of that, his product offered more than double the capacity of the 5S38S. It really wasn't any ruder in hand than the snub revolvers of that day, either.
Limited company size (with limited marketing and production ability), questionable quality, and a lack of enthusiasm for a misunderstood placement all contributed to the gun's failure.
That was my first .380, and I did routinely carry it off duty for almost a year, in a pocket without a holster (pocket holsters really weren't much of a thing back then, and the Grendel fit nothing.) I never put it on an ankle because I never found a rig that it fit well. It would have ridden nicely down there.
My next .380 was an Interarms-Walther PPK/S. Very nice weapon, which was on the "approved roster" for the second agency for which I worked. That one did BU/OD carry for a year until I left the job. I sold it not long after that. I really liked it.
In 2008, I got back into firearms and picked up a Bersa Thunder 380 to kind of replace that old Walther. I can't say enough about the reliability of the BT; it's rock-solid and not that rude in hand as I remember the PPK/S being. I carried it for two years until I came across a Kel-Tec PF9 (then in high demand) and switched to that. I still have the BT380.
In 2016, I picked up a last-generation Taurus TCP (before they discontinued the model for the Spectrum.) It's handsome and has yet to malfunction, and is as rough in hand as the PF9. I was already carrying a P32 as a BUG, and had no intention to quit that, so I really don't know why I bought the TCP. The price was really good, though.
Now, I have the LCP MAX.... (OOB impression and range review posted in separate threads.)