[603Country]

rtpzwms, having read this discussion a couple of more times, I'm wondering why you want to do a shoulder bump of the cases you are going to shoot in an AR. Admittedly, I'm not an AR pro, having had to return the one the USMC loaned me. That said, if your rifle handles regular factory ammo well, then I think I'd just resize the cases to factory (SAAMI?) specs. You shouldn't need small base dies for that, I'd think, and the small base dies will work your brass pretty hard.

I believe that you can purchase some different shellholders that will allow the regular FL dies to bump the shoulder back a touch more with standard FL dies. I'd give that a try. I can't see any need whatever for you to buy or use neck sizing dies. That won't fix any problem you have.

Again, if the rifle feeds and shoots factory rounds, there's nothing wrong with the chamber size. Standard dies should work, if they will size the brass to factory dimensions.

There are bound to be some reloading tricks the big-time AR guys use, but I don't know them. I reloaded for a BAR in 270 for years, and did use small base dies for it. The more I got into reloading, the more I went toward bolt guns for better accuracy and longer case life, and not having to look for my fired brass. :-)