Hello All, First time poster here on Glock Talk. I have a question for the collective minds here in the reloading area and thank you in advance. I recently purchased a Glock 17, which I should add has been accurate and flawless through the first 1000+ rounds of various brands of factory ammo. My issue is that I've begun reloading for range and training and, as is my usual procedure, I pull the barrel from the gun and drop the first 100 or so loaded rounds in the chamber to make sure all of them fit properly. Out of the first 100 rounds 16 would not chamber fully. I measured them to find that they are .390-.391 at the pressure ring. All of the rounds that chamber are .388-.389. The brass I am using is various range pickups. Also, the cases that don't fit are various headstamps. Depending on the manual I check I find that 9mm should be in the .391-.392 at the base of the case or pressure ring. These rounds that do not chamber in the Glock will chamber in my Kahr PM9 and Ruger P85. Also if I load these in a magazine they will fully chamber when the slide is racked but become stuck needing to be pushed out. I have not tried firing one of these that way as I'm not sure if it would cycle the slide or break the ejector claw off. So, if you're still awake after my rambling, my query is do Glocks have a tighter chamber than some other brands? Also, is there something I can change during the reloading process so that I won't have to check every round I load to make sure it fits in the Glock chamber? All of my reloads fit my other 9mm guns. Thanks again, Wanna kill these ads? We can help!