Greetings,
With the changes in CCW laws in my state I am now planning to use my P40 as my carry weapon, given I have only used it for target practice I have only every purchased target ammo and I am looking for recommendations to use for carry ammo.

Thanks!

I use Federal Personal Defense HST in my Kahr 40.  Functions flawlessly.

I use 165gr Golden Saber bonded.

The Ranger T series 180gr. bonded is a excellent choice if you can find it.

With a used gun you're putting into defense use, my first move would be to buy a new Kahr factory recoil spring.
These small guns are hard on springs.
Buy A FACTORY spring, not an aftermarket of any kind.

Give the gun a good deep cleaning, including the firing pin system and fresh lube.
By whatever brand and type of ammo you want (or can find) and shoot enough of it that you're satisfied that the gun-magazine-ammo combination is 100% reliable.
How much ammo that takes depends on your money supply and on how lucky you feel.
Personally I go at least 100 rounds.  With premium American made defense ammo that can be expensive, but how much is your life worth?

When buying premium American defense ammo, the brand and type you buy is not at all important, it ALL performs as well as a pistol round can perform.
The ammo that's 100% in my gun may choke in yours, so recommendations are pretty useless.
The only thing that really counts is reliability....not accuracy, not supposed "stopping power", not some review.  
It's whether THAT ammo is reliable in THAT gun, and with THOSE magazines, in YOUR hands.

Good points.
So how does one search for and find "American defense ammo"?

American made premium defense ammo is what it says......Higher priced hollow point ammo made by an American company and usually with a name like "Personal Defense", "Ultimate Defense", "Critical Defense", etc.
It's sold specifically as defensive ammo.

This is almost always 20 rounds to a box and is expensive, usually at $1.00 to $2.00 a round.

You can find it online at places like Midway, and often at good prices at Rural King as well as most any local gun shop or many big box outdoor and sport stores like Cabela's and Academy.

https://www.midwayusa.com/40-s-and-w/br?cid=21804

Note that verifying total reliability out of a gun-magazine-ammo can get really expensive at those prices.
This can lead you to firing a magazine of that high priced and hard to get ammo and calling it good, which may come back to bite you in a real "situation".

Thanks brother!