One thing to check is the extractor. I was having issues with Federal brass until I found this picture. A little bit of work and the problem is solved.
Is this common to Grendel extractors? The extractors on my faxon bolts look the same. I don't have fte or ftf problems, but my brass does get marks on it.
Common enough that there's a few threads floating around the internet. I had marks on hornady brass, but federal would cause extractor issues. It's an easy fix though.
Yeah, knock off the sharp points to make it look like the other extractors in the picture above. I removed the extractor from the bolt and used my dynafile, but anything would work as long as you take your time.