No problem, we get all wound up and shoot off (pun) and forget others are scratching their heads (trust me, my wife and I have to work hard on that!)
Also, always check data as we can make mistakes on typo and thats not good.
Ok, no rule of thumb, its just too powder specific and too many variations of burn rate to work that way. Takes a lot of research.
From personal experience I started to use TAC in 30-06 Bolt (desperation as I can't get more powder and keeping the 4350 etc for certain guns that like it).
Sierra lists 41 gr as a starting load (bolt).
Ram-shot says, well, its ok, but their starting was well above that as it was for Garand (they don't think its a good load for bolt). They say for the M1 though, Big Game? is better suited.
Back to, its all about burn rates with an M1 and correctly cycling and done right those fall in a safe category (no one is going to max out an M1 to take that elusive Bull Elephant in the back yard (grin).
So, for the M1 you have to get as much data as you can and if it was me, I would load in right between low and middle of that not the lower range. Let others more experienced of course give you better skinny. It may not cycle your gun at low.
For the TAC and the 30-06 in a bolt, 41 grains! That charge does not fill the case but shoots well in some guns (Model of 1917). People are leery of it because of the lot of empty case capacity, but if Sierra says ok, I am good with its not only ok, its a safe low ok for BOLT.
Just found the ref.
For my 168 load area (Ramshot lists 168 to 175 for this load in Garand.
45 min to 50. I would start at 46 or 47.
So, for bolt Horandy and Sierra are my go to (and throw in a few others to see what how the powder loads ranges look.
For M1, contact the powder mfg and or keep looking at the tables but always be sure its an M1 specific load. I don't have any books that tell me they used and M1 though. Sierra does give two tables for AR and Bolt in 223.
Military brass supposedly is thicker and if its not specific to military brass drop a grain or two. Me, I am weighing shells and military is less weight than civilian in some (only real way to tell is measure case capacity).
Thicker means a few less grains. If you are in the middle you don't have to worry about it.