This is getting a little complicated. If I purchase once fired Lake City brass due to it's reputation for longer brass life I will then have to buy a small base die and shorten the brass life of the Lake City brass? Wouldn't I be better off staying away from the military brass altogether?
Although there is a good bit of information here about sizing brass, etc, for semi-autos... I have a different reason to avoid once-fired military brass: Catastrophic failure.
Right after I bought my M1a, I also sourced 2 separate lots of 1000 'processed, once-fired' military brass from one of the major vendors. This was 2008 or so, so the majority of the headstamps were LC 04/5/6/7/8, along with some other stuff (Winchester, old LC, old LC LR, PMJ (PMC) and similar.) 'Processed' means it was sized, cleaned, and had the primer pocket reamed. Concentrating on segregated groups of the LC brass, since it was the largest, I loaded everything up with my standard M-80 equivalent load. And then the cases started failing.
Oddly enough, case head separations, generally caused by case stretch from firing in loose-chamber machine guns, was rarely an issue. What I experienced was complete case head failure... and this on my FIRST firing (or, the second for the case.)
This ALL with the LC brass. Initially, I thought I had it isolated to the LC04 headstamp, but as I tried to work my way through the other date codes, they started failing, too. It's possible it was poor brass quality, but I don't believe so... personally, I believe the brass was contaminated after firing, while being stored awaiting disposition (auction.) I have a number of reasons why I believe this to be the case, I won't bore you with the details.
The cases fractured on firing, blew gas in my face, and blew the bottom of the magazine out, dumping the contents on my feet. If there ever was justification to wear quality shooting glasses... I sure found it.
As far as the other brass... the Winchester brass all failed from either cracked necks, or case body...
The only case head separation I had was with a single piece of PMJ...
...although I found more incipent separations when checking the brass...
Again... all this on the 2nd firing.
At the end of the day, I had to scrap nearly 1700 cases... everything except the bit of PMJ brass. That brass is still in service, on it's 3rd or 4th firing, but I will likely retire it after the next firing, or load it up (after inspection) to fire where it's likely I'll lose my brass... and let it go.
My replacement M1a brass source is currently from factory Prvi ammos. I bought a bunch of it when I got my M1a. As I take my other brass out of service, I put the Prvi into rotation. I have never lost one Prvi case due to a failure or separation.
I also have 2 lots of newer LC brass... one lot from 500 'pulled' cases, and another 500 lot from factory ammos... so NOT once-fired, but virgin brass in one respect or another. Both lots of this ammo have corrosion spots, basically from day 1. Much of it is topical... I worked with another member (on another forum) to wet tumble some of the suspect brass, and it all came out clean, with just some minor specs of etching. Given my track record with LC brass, I HAD to know before I continued on with it. Again, at the end of the day, I'm done with LC brass (in .308.) I'll load these 1000 LC cases for as long as they last, and that will be it.
Edit to add: Case head failures occurred in both my M1a, with the gas valve turned on and off (to try to isolate the problem,) and even in my .308 Savage bolt gun... so it was NOT an issue of the violent M1a action or cycling.
Conclusions: I no longer use anyone's once-fired rifle brass, I only use virgin brass components, or brass from factory ammo fired by me, in most cases. I know there are a thousand examples of people using once-fired brass, range pickups, or whatever, with perfect success... compared to my one example of failure, but it comes down to acceptable risk and what I can do to control that risk
for me. YMMV.