If anyone has ever had trouble reloading .223 Rem/5.56 for an AR15 where the resized brass will not pass a case gauge and you are getting some reloaded rounds jammed in your AR like I was. I finally found a solution. I have been reloading for over 40 years before starting to reload for an AR15 and ran into a problem with reloaded rounds failing to chamber completely. I did the search thing on all the chat rooms and tried every thing even a new set of small base dies. Bought a Lyman case gauge and found about 10% of the reloaded military brass would not pass a Lyman case gauge even after going through and RCBS small base die. I put a micrometer on the case head and found the ones that failed to gauge and jammed my AR15 had over size case heads or rims, that is they were over .376" at the widest part. That's when I started a search for some thing that would resize the case head. The only die I could find was on the Wholesalehunter web site called "223 Remington / 5.56mm NATO Case head Sizing Die" . I bought one and ran over 100 rounds through the die that had failed to pass the Lyman case gauge. After I ran them through this die they all passed the case gauge. I also fired all of them thru my AR with out a single jam. Works like a dream. I think that when I used an RCBS primer pocket swagger on some of the military brass, it may have caused some of the case heads to expand and that's why they gave me trouble. But I found a few commercial pieces of brass that failed to gauge too before I ran them through the case head sizer. I hope this information is useful to anyone having the same problems that I was.