I'm working up some loads for my 9mm using a 125 grain lead round nose and Longshot powder. The Hodgdon 60 year flyer shows 5.7 grains of Longshot behind a 125 JHP. I put the same amount of powder behind the lead bullets, figuring it would be quite safe. The lead bullets have a pronounced shoulder, and are seated to match that shoulder with the case mouth, giving an overall length of 1.106". The taper crimp measures .379 inches at the neck, .001 under the specification for the cartridge. The rounds drop freely into the chamber. I ran a single shot of 115 grain American Eagle JHP, then 2 shots of the same, followed by the lead handloads. The first factory load chambered and fired. But then things didn't work. The slide failed to fully close after firing the first handload. I tried pushing it into battery and it still failed to close. I brought the gun in from the cold. I tried to chamber a factory round by releasing the slide with the slide release -- didn't chamber. I tried to chamber one of the handloads -- same thing. I tried to close the slide on either one by hand -- no go. I took the gun down, and found a 125 grain lead slug just barely started into the rifling, blocking the barrel and chamber (VERY fortunately!). There had been no major difference in sound or felt recoil between the factory 115 grain FMJ and the handload. Granted, I was wearing muffs, and it's cold out, and I don't have a lot of time with this particular gun (a P95), but there should have been something different enough to notice. There was not. The spent case ejected, but fell at my feet instead of back and to the right several feet. I was very lucky that the bullet stuck close enough to the chamber that it prevented the next round from chambering. I don't relish the thought of trying to shoot a 250 grain bullet from a 9mm, which is what I would have been doing had the next round chambered. At this point, I am presuming I need more powder. The Hodgdon data show 6.0 grains behind the Speer 115 gr Gold Dot HP. and 4.7 behind the 147 gr. Hornady boat tail HP. I will be checking their website for additional information. Today's lessons, class -- 1) When working up a new load for an autoloader, always single load several before trying a magazine full. 2) Do not presume you can transfer powder data from jacketed loads to same weight lead bullet loads.