Thunderbolt is all my p17 shots reliably.I got my repaired P 17 back last week (in due to failure to feed 100% of the time). I loaded up the mags with Rem Thunderbolts as these are the rounds that my CP33 LOVES. When I racked the first magazine, the nose of the bullet stuck in the feed ramp as before. I partly re-racked and the bullet then went in the chamber. I fired the pistol and all of the rest of the rounds worked just fine with zero issues. So, I put in the second magazine and the very same thing happened, Failure to load the first round, then, all the rest worked perfectly. Third mag, the very same issue. I then reloaded all three mags and all six times, the first round got stuck in the feed ramp then all the rest worked fine. I brought the gun home very ticked off since it had been "repaired" for this very issue. Noting that Keltec test fired it with CCI Mini Mags, I loaded up one magazine with them as well as one mag with Federal Auto Match and the third one with Wildcats. All are 40 grn lr high capacity--just like the Thunderbolts. Guess what. All three mags worked perfectly! It looks like the P17 will not work properly with Thunderbolts but it is fine with other brands. Weird but that is how my experiment went. When working, both my wife and I love this pistol. Now, The CP33 AND the P17 are the wife's favorite pistols. Will post further only if the failure to feed starts up again. Will shoot it more Thursday.