I have a Savage in 6BR with a McGowen 8 twist barrel and have noticed something interesting regarding the powders the rifle prefers. I've tried nine different powders (I love doing load development). Four were single base and the rest double base and all had various burning rates from fast to slow for the 6BR. The least accurate single base powder, Benchmark, gets significantly smaller groups than the best double base, H322. I'm glad the rifle likes single base since they burn cooler and should make for longer barrel life. Is something like this common?