I remember having a conversation with Tom Whittaker about loading for 1000 Palma (308 w155 Sierra) about this very subject. He built a special gun to shoot BBs with just the primer. He could then shoot in his workshop over a chrono into a stop. The theory was to find the better ES and SD then confirm at the range and 1000. Spent $1000s on primers and found that while some lots of RWS was good some of the time, other lots were “expensive 600 yard primers”.My recollection was that the testing that Mid Tomkins/Bob Jensen did, found that the mildest primer that would reliably ignite the charge would give the best ES's which was vital for flat elevations at 1000 yards. They found that the RWS met that criteria. I used a few thousand of the 5341 code twenty or so years ago but to me they didn't seem any better than the Federals I had been using and being slightly smaller diameter I was having to bin brass as the primer pockets opened up