It takes a huge amount of time, money and testing to develop a new loading manual. That's why it's so long between publishing dates. Look how long it takes people on this board to develop a load they like for just one bullet, in one caliber.
If you can manage to finagle a tour of one of the bullet companies, by all means do so. I've toured both Nosler (twice) and Sierra's plants and have visited their ballistics labs/ranges. It still amazes me that they're willing to invest all that time and money and still publish their manuals for what they sell for, and in a lot of cases, provide the data for free..........
Hope this helps.
Fred