There is NO SAAMI STANDARD for +P in .380.
S&W specifically states the warranty is only good for SAAMI standard ammunition.
So what is being asked, and talked around, "If I use .380 ammunition that is over SAAMI pressure standards, 1. Will it blow up the gun? and 2. Will the warranty still be good?"

1. What is the pressure? Chances are, the currently sold "+P" is about the same as a .380 Proof Load, so probably "No." Certainly continued shooting of proof loads carries risk.
2. It shouldn't, but a dishonest person might lie about the ammunition and get something.

I have tested .380 handloads in a SIG right up to max as listed in an old Hornady manual, to the point cases had obvious damage including loose primer pockets and case splits. The gain in speed over a few tenths less powder (that did not damage cases) was not worth it.
Ballistically, it was still a 9mm Short, not a 9mm Luger.

It is not the first time I've seen max loads that gained little by going over the limit.

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