The original takedown pin that came in my LCP repeatedly walked halfway out during the first range session. Ammo was a mix of standard JHP's from some of the major makers, too, no hot-rodded or ".380 +P" stuff.
I called Ruger and they sent me another pin. That one hasn't exhibited the same problem over more rounds than it took for the first one to exhibit the problem.
Out of curiosity, I ordered one of those aftermarket takedown pins advertised to make takedown easier. It basically traps the wire spring in a short (but deep) machined groove on one side of the pin. A slot screwdriver can be used to turn the pin so the wire spring is freed from the groove, making it easier to pull the pin from the frame for field-stripping.
I didn't order it to make takedown easier, but was wondering if the deep machined groove might better retain the wire spring (compared to the shallow recessed shoulder of the factory pin).
Again using a mix of some different major American factory loads, the pin walked hallway out of the frame after approx 50 rounds. It appeared the pin had rotated under recoil, which would have turned the pin and released the wire, at which time the wire spring wouldn't have any resistance to prevent slippage of the pin.
I reinstalled the second factory (replacement) takedown pin in the gun and fired more rounds, with the pin once again remaining in the frame. I'll continue to use that second factory pin.
Maybe there's a reason the Ruger engineers designed the shallow shoulder to extend all the way around the takedown pin's body, after all?
If the pin normally rotates under constant recoil, the shallow shoulder would still continue to provide resistance against the wire spring.
So, the aftermarket takedown pin will get put into the box of widgets on which I've wasted money over the years.
FWIW, Ruger had no explanation for my first pin walking under recoil. Seeing how shallow the shoulder edge is compared to the diameter of the wire spring, though, I could see how maybe the odd pin just might not have enough shoulder edge to hold the round wire spring and keep it from slipping over & by, under recoil.
My LCP was made in mid-2012, BTW.