Ruger's manual carries what appears to be a standard warning "Do not use "+P" ammunition." There is no SAAMI standard +P ammunition in .380 ACP.
But just before that it says "No .380 Auto ammunition manufactured in accordance with NATO, U.S., SAAMI or CIP standards is known to be beyond the design limits or known not to function in these pistols."
FWIW, I miked my LCP and the thinnest part of the chamber measures .038". Probably adequate, but not a lot of margin for error. Old time designers (e.g., Browning) didn't have the modern steels and measuring devices we do today, so they made everything thicker and stronger than it had to be, then made it even thicker and stronger. The result was lot of useless weight and bulk. But one does wonder if the trend to light weight can go too far in the opposite direction, leaving too little margin for mistakes.
Jim