rtpzwms,
Out of curiosity, was the brass that failed to chamber once-fired brass?
It's not unusual to need to use a small base die on once-fired brass because it is often stretched way over normal by extraction from a SAW. Such brass can have too much spring-back to be properly resized by a standard die on the first pass. Even previous firing in a loose AR chamber can make it too big to be sizes all the way down for a tighter chamber by one pass through a standard die.
Board member F. Guffey likes to cut shim stock to fit between the case head and shell holder's case insertion slot on the bottom side so the case if forced further into the sizing die than normal. This can make a standard die work for the first pass with badly stretched once-fired cases. But once you've fired the brass one time in your chamber, the standard die should work thereafter unless you have one of the few AR's I mentioned before. If you do have one of them, I would recommend checking your magazine lips for proper release timing (try some surplus military ones for comparison). You could also gauge the rifle completely, if you have the armorer's tools. The few picky AR's will have something different bout them than can be measured somewhere. I just haven't had one in my hands to figure it out.
The case gauge won't necessarily tell you if your cases are too fat. Dillon tells me they cut theirs with a chamber reamer to SAAMI chamber standard minimum, but that is a full thousandth larger in diameter than SAAMI maximum case size, and most commercial new cases are about 0.004" smaller in diameter than SAAMI maximum. So about 0.005" would be the diameter clearance for a typical new case going into a SAAMI minimum chamber. What you know from the gauge is that any case it accepts will chamber in a bolt gun loading singly, but that's not going to guarantee you suitability of the diameter for magazine feed, which will need to be at least -0.001" smaller than the gauge diameter, and -0.002" or more is better and -0.005" is normal.
As to the Redding Body Die, if you are using a Lee Collet Die to size the neck, a body die will work fine to size the rest of the case, as it doesn't touch the neck. The Lee die leaves necks very true on runout, as
this video demonstrates, but they only size the neck. But if you are looking to resize the neck and body all in one step, get a Redding S type full length sizing die in the size you want and let its neck bushings do the neck sizing.
The Forster bump dies are not small base and don't size the case body diameter at all; they are a form of neck size-only die, that also lightly bumps the shoulder back to center it and the neck up. It won't help with a diameter-related feed problem. Moreover, if you neck size-only for a military style self-loader with a floating firing pin, you increase the chance of getting a slamfire or worse, an out of battery fire, so there is hazard associated with doing that (more for the Garand and M14 systems, but just not zero even in the AR). This hazard would be made worse if using the bump die exclusively with once-fired brass. It's really a tool for benchrest bolt rifle shooters.