Well, i took my Kimber Micro Raptor to the range yesterday with 40 rounds of Underwood 90gr. +P XTP's. I've already confirmed the XTP functions fine by shooing approximately 200 rounds of Hornady Custom, Hornady American Gunner and Black Hills through my Micro. I used 3- 6 round magazines topping them all off just like I carry. The last mag had a couple of FMJ's at the bottom. I'm using a Sig P238 recoil and firing pin spring. I also brought Wolff extra power mag springs, for a Colt Mustang in case I ran into timing issues, which I did not. All rounds fired and ejected perfectly. Recoil is noticeably warmer than standard FMJ loads, but not nearly as hot as I expected. They probably would be a handful in an LCP, but I never like shooting my LCP with anything. Accuracy was decent for me holding a 5" group at 10 yards. My local indoor range won't allow me to use my chronograph, but my guess is muzzle velocity is somewhere in the ballpark of 1075 fps. I never thought getting hit by a .380 would be fun, but this stuff will definitely leave a mark.
Yes, it's still a .380 and shot placement is still king.
I must confess I was a little hesitant in using this ammo, but my concerns were unwarranted. It's simply no big deal. Though I won't shoot this ammo on a weekly basis, burning through my carry ammo twice a year should be no problem. I also give props to Underwood, their quality and customer service is second to none.