Folks who claim that using a small base die shortens case life are doing something that I am not. Perhaps they are not setting up their dies with Wilson type case gages. A small base die will oversize a case if you do not know how to set the die up.
http://www.realguns.com/Commentary/comar46.htm
Gas guns depend on good ammunition to function. If your cases are oversized, or undersized, you are going to have problems. You want cases that are close to factory dimensions for best feeding and extraction. The AR is relatively forgiving in this matter, it does size slightly oversize cases to fit the chamber, and if it slamfires in the process, the lugs are usually in engagement. Something that is not always true for the M1a or Garand.
The gunsmith who rebarrels my match rifles always has someone calling in, complaining that their newly rebarreled rifle is jamming with their reloads. The problems with their reloads were that the ammunition was fired in some huge chamber, then the owner sized them like they always did with a standard die, and those cases become an interference fit in the chamber of a new match AR.
And what do you know, just after I posted this, another thread shows a guy who uses a case gage, but not small base dies, and his cases won't come out of the chamber, easily.
http://www.thefiringline.com/forums/showthread.php?p=2970854#post2970854
As for limited case life, I have not experienced it. I small base size .223, 308 and 30-06. I shoot the stuff in match rifles and standard grade rifles.
As a science experiment, I took one set of 308 LC64 cases 22 or 24 reloads, in a M1a, using small base dies (and lubricated cases!) and never had a case head separation. I had body splits, neck splits, and I retired the brass when the primer pockets got too large.
Some of my AR brass is around ten reloads. That is the stuff I use for load testing. No unusual overworked problems yet.
Standard dies may not reduce the case enough to drop in a chamber. Barnett, the barrel maker, made me 308 and 30-06 case gages using the same reamer he uses on his M1a and M1 Garand match barrels. At that time I think he was using J&G reamers. I could be wrong. Wilson type headspace gages are cut fat, so you can drop in a fired round and measure headspace. Wilson gages do not measure “fatness”. As you can see from the attached pictures, cases sized with a standard sizing die are not necessarily reduced enough to fit in the reamer cut chamber.
This small interference fit would never be noticed in a bolt rifle. The cocking cams are so powerful. But I don’t want any delay to bolt closure in a gas gun. The small base sized brass just dropped right in.
I paid Compass Lake Engineering $35.00 for a .223 reamer cut cartridge headspace gage, using their reamer. That is the reamer they used on my Space Gun barrel. I do not have any similiar .223 pictures, but generally the Lee Die sized .223 cases just drop right in. Still, I use a Lyman Small base die on my .223 brass. Works great.
As for accuracy, if you can hold hard enough to tell the difference in accuracy between dies, standard dies and small base dies, NRA week at Camp Perry is next week. Go now. Because you will win everything. Two weeks from now you will be the National Across the course champion, and probably the National Long Range champion. You just missed winning the President's 100 and the Leg match.
Unsized, once fired 308 cases. One in a Wilson case gage, one in a reamer cut chamber gage.
Case sized in standard die. Does not drop flush into reamer cut chamber gage
Case sized in small base die. Drops flush into reamer cut chamber gage.
