I put together a 6.8SPC 18" AR15 carbine several years ago, and had some SSA brass to try in it. Got lousy accuracy with several different loads, and had set the little gun aside. One or two of the reloading supply places I usually do business with finally got in some Hornady SPC brass, so I tried it - accuracy improved considerably, with no other changes. I sold the carbine to a friend who wanted it to use as a deer rifle for his daughter, and she's nailed a buck with it every time he's taken her out hunting, so I'm not getting it back, nor have I had any way to test other brands of brass. If I were to get into another 6.8 or a 22cal or 6mm wildcat based on the SPC case, I'd probably buy a 250ct bag of brass from Starline.
When I started building my 6.8 SPC, I went with the SSA (Silver State Armory) brass. Mine was built on a Savage bolt action. No problems getting bug holes. Brass holds up well with no issues. All mid range loads so the brass never got hammered. Primer pockets stay tight. I had heard way back when that the SSA brass was made by Nosler. Looks that way now.
What Caliber Fast?I've been shooting the 6.8spc in silhouette comp for the last 5 years, I've tested all kinds of brass. My favorite has been Sellier & Bellot. My current batch is on 8x firings and primer pockets are still nice and tight with over book max loads. Next would be S&B made Hornady stamped brass. Subtle difference in the head stamp, but both of these have the highest capacity with excellent uniformity. After that would be old batch SSA, but primer pockets dont last long. Hornady made hornady stamped brass is pretty good, though lowest volume and can vary quite a bit. Nosler has proven to be nosler quality, hit or miss.
When I'm shooting paper at mid range I use cnc turned 120gr match bullets, but for silhouette and other stuff, I run the Hornady 110gr BTHP.