This has been debated for years and will continue to be talked about .
Robert Churchill promoted his 25 " barrels but in the last thirty years barrels upto 32" have been promoted.
I think we can all adjust to shooting any length of barrel , because many of us cannot afford to change on a whim .
King George has tried 34" but didn't like them and settled on 32".
John Bidwell became Sporting & Fitasc World champion with 28" barreled Browning before moving to 30".
So I think we can all have success with whatever we choose and practice with.