Using the Pressure Trace to get real world data was THE biggest eye opener for me. I had QL and ran the numbers side by side, what it showed me was this.
For my wildcats based on the 416 Rigby Improved (not AI) case, I required a barrel of 30" minimum and optimum lengths ran into these lengths: 30 cal = 34", 33 cal = 32" & 37 cal = 30-31". I dabbled with .408 cal and it said optimum was 31-32" which I questioned, but the bore size fell off sooner than the others.
Now, taking all that into consideration, and ease of implementing blank sizes, I erred on the shorter lengths because getting blanks to finish at 34" here is a pain.
So, my barrels run, 32" for 30 cal with 35° shoulder, 32" for 33 cal, and a 30" barrel for 33 cal 45° shoulder & 30" for 37 cal 40° shoulder. Twists run 10" for 30 cal, 9" for 33 cal & 10" for 37 cal which is super fast I discovered. The 300g SMK didn't like this twist…
The only known cartridges to me that up this performance, are the Allen Magnums based on the 408 CheyTac case, which is essentially the altered 505 Gibbs case, which I had one for several years. Unbelievable cartridge pushing 600g pills at 2500fps, if desired, I did it once! Never again in a 9lb rifle.
Anyway, if you want the utmost performance, long barrels are required to burn the powder and to get the desired velocity.
Cheers.