I've been reloading for over 50 years...all types of metalics and shotgun. I built rifles and reloaded for 22-250 and 25-05 BEFORE they were factory calibers. Just telling everyone this so you know I've been doing this awhile. I have a commercial Mauser actioned .300 Wby that was given to me. It was imported by Stoeger in the 60's. Nice gun, but wouldn't shoot well at all. Would not group, no pattern to shots, just all over the map. Looked at the barrel and it was shot, lots of throat erosion. No telling how many rounds had been thru this baby. I had worked out a load that would shoot the best, but not good at all (at least for me!), best I could do was about 5 minute groups, yuk!! Put on a new Shilen match SS barrel and started breaking it in. With the other baseline load and some factory I had, the best I could do was about the same as the old barrel (huh!). Started from scratch. Inspected all cases, checked for OAL case length, full length sized and reprimed them. All cases are Weatherby. I like Nosler Partition for elk, but decided to load up some Sierra spitzer BTs too. I really like Reloader 25 for the big cap cases and this is my powder of choice. Loaded up 3 ea of each powder charge with 1/2 grain increases from the lightest load. Did the same for the Nosler and Sierra bullets. Went to the range yesterday and did a little work. None of the Sierras shot well at all. I got to the last 2 Nosler loads and got one group that all 3 holes were touching (at 100 yds). I now felt a little better. The load that shoots the best.....a 1/2 grain LESS than what I had tried initially (my old baseline load). Go figure.....never in all my years reloading did a half grain of powder make THAT much difference. Now I'm loading up a few to take to the 500 yard range to seal the deal (I hope).