I agree. Load 5 with the original BTO measurement. You still may need to tweak it a few thousandths. Your seating die setting will definitely change. Let us know what you find out.
I'd look at a 22BR if you don't already have an action with a .223 bolt face. Or if you are set on 20 caliber, a 20 BR with 50 grain bullets in the neighborhood of 3800 fps.
https://www.6mmbr.com/20Caliber.html
I'd change direction completely. Get yourself a new BAT action and build something much cheaper to shoot, easy on the shoulder, easy on powder and probably the most consistently accurate rifle you'll own......a 6BR.
It depends. Is the bullet touching or in the lands at the length you're shooting?
Do you have any idea how much free bore your chamber has or where the bullet is in relation to the lands? I'd be very careful if I were you. Things can change in an instant when you are running on the edge.
https://www.businesswire.com/news/home/20171107006347/en/Top-5-Vendors-in-the-Nitrocellulose-Market---Technavio
Since we all know what Covid is.........
https://www.defense.gov/News/Releases/Release/Article/2885655/dod-awards-1367-million-contract-to-milliporesigma-to-establish-domestic-produc/
That is 10 times, or 800% more than I was paying just 6 years ago. There is no way that manufacturing costs have risen that much in that short of a time. When are people going to wake up? :rolleyes:
Like you said, you already have a 30-06. Build a 6mm BR with an 8 twist barrel. It would serve all of your purposes well and be the most accurate rifle you ever shot with good components and ammo. It'll get you over 200 rounds with a pound of powder as well.