1907 small barrel .416

This is my first post so please bear with me. I have a Savage 1907 ser. # 11829. The barrel is corroded. I asked the collector I bought it from if he might have a better barrel. While trying to find one we discovered that this barrel is smaller in diameter than all the barrels he had. He then took another 1907 from his collection from the same year of manufacture and it also had a larger barrel than mine. He has been collecting Savage products for many years and has never seen this before. I have checked every post for 1907s on this forum and only found one reference to the .416 small barrel. It only mentioned he had one but no information about what it is and why the difference.

Do you have any information about this anomaly?

Thanx for taking the time to read this and I hope it has piqued your interest enough to reply.