It is a stupid risk if the gun is not designed for it. Take a Beretta Pico, or Kahr and break the gun down. First of all look at the stainless steel barrel and then the sub chassis which in both guns is stainless steel vs aluminum. The Pico is all stainless in all parts of the gun except the polymer grip which is a Modular design. The Kahr is also stainless steel, but also has steel inserts in the grip at the stress points.
I have shot these guns with Plus P ammo and many rounds through them. You can go ahead and take others advice that Plus P ammo is not real simply because Saami does not include 380.
If you feel like they are right then go ahead and start shooting some plus P ammo and see the results for yourself.
Also the Kahr and Pico are both guns that will go indefinitely with a considerable amount of ammo down range. From experience I know the limitations of the cheaper aluminum sub-chassis firearms. They will go down and as early as 1500 with just standard ammo. I have one Pico that has three times that amount and running strong as ever. I just make sure I change the recoil springs on a regular.
So If you believe that I am not be truthfull, or full of BS then the only way is to find out for yourself and start shooting Plus P. But beware. That is my advice. You can listen to others on the internet if you like, but I would err in caution before taking their advice. I have had many LCP's go down. And Ruger will ask you if you have been shooting Plus P. If you are honest, and say yes, they will not replace the gun.
Go at your own Risk!
Steel inserts in Kahr grip frame
Pico grip frame
All steel sub chassis.
Barrel in the Pico for instance is Heavier
Slide is stainless steel and heavier.
Notice how the Pico has a Stainless over built take down pin. I have broken many in shooting the LCP's over the years.
Again, If you believe there is not such thing as Plus P and want to not take the advice from the owners manual, shoot Plus P ammo through a aluminum sub chassis gun, then Please go for it and find out for yourself. But
go at your own Risk. And if you get hurt or destroy your gun, just tell them, you saw on the internet that there was no such thing as Plus P. Good luck with that.