My P-11 likes Cor-Bon Pow'r Ball, Hornady Critical Defense, and my practice hand loads using Ranier 124-gr plated HP as long as I load them to 1.1" overall length. It tends not to like hollow point projectiles loaded over 1.1".
It can be finicky feeding Speer Gold Dot 124 gr, which is loaded to about 1.125" overall. I keep Gold Dot in the chamber (where feeding is not a concern) and it seems not to mind feeding them further down in the magazine. It just doesn't like them in the first four slots or so.
The main thing is to test your desired carry ammo in your weapon until you are satisfied and confident. I know it is expensive to shoot much of the self-defense ammo you intend to carry, but it is necessary.
Remington UMC JHP (usually keep loaded with these because they are cheap and I know what they will do), WWB FMJ, Federal FMJ, Zombiemax (same as critical defense but with a neat box and green plugs)
Manually feeding rounds, the hornaday stuff sticks a little more than the others because of the little rubber tip, but I haven't had a FTF yet...
At the range I generally shoot Winchester White Box 115gr FMJ or Federal 115gr FMJ both from Wal*Mart. I have never had any problem with ammo of any kind that I've shot through it. I generally try to shoot U.S. Made ammo. I received a memo from Kel-Tec that said not to shoot aluminum or steel cased ammo through this gun.
For carry ammo, I've been carrying Hornady TAP 124gr JHP for over three years. It shoots great out of the P-11 and has performed very well during my ballistic testing. - It is a little hotter than standard pressure 9mm, but not quite as hot as +P. I have also shot Remington Golden Saber 124gr JHP as well as Speer Gold Dot 124gr JHP and PMC El Dorado StarFire 124gr JHP and they have all worked great.
NOTE: Kel-Tec did polish the feed ramp the last time they had the gun for repair, but I have never had any problem with it firing anything that I feed it.
Speer Gold Dot 115gr standard pressure sits in my P11 and PF9 magazines. I did have Hornady Critical Defense in the P11, but I switched that over to the SW9VE because that's might bedside pistol and I figure the low-flash powder of the HCD's would go well with that for night-time indoor defensive use. Well, that and I hear the PF9's don't care much for Hornady's slightly smaller-than-average case rim size, although I haven't fired any through the PF9 yet to know for sure just yet...
Just returning from the range where I shot 5o federal fmjs thru my older p11 with no problem and good results. Last range trip I shot my two p11s and had a 5% failure to fire on the newer one and a 20% failure to fire on the older one using wwb fmjs. The older p11 has a distinctly lighter trigger, even
thought it's only older by a month. (bought new Sept and Oct 2012) Both pistols were 100% on the seccond trigger pull. Fired wwb in my sr9 today with no failures to fire which has been standard with that pistol. So I try to avoid the wwb in the P11s. The federal fmjs simply have superior primers.
I use federl hydra shok for carry and have had no failures with them..
On the other 'best ammo' thread I cited Federal 115gr FMJ standard for range and Copper Only Projectiles 115+p JHP for carry. Need to get some more Federal or Winchester...or anything for that matter. Just not going to allow myself to be gouged, so I await the WM score. It'll happen. One just needs patience.