I think that at 50mm they start detract from both the appearance and functionality of a hunting rifle. 40 to 42 mm is big enough to take in as much light as it takes. Any gain beyond that is so marginal as to be barely worth mentioning.

To some degree, IMHO it's as much about marketing as anything else. Bigger is better, rah rah rah, and all that stuff.

Thinking about it, even the forces snipers tend towards 40mm scopes. Quick check, gleaned the following info from...

http://en.wikipedia.org/wiki/C14_Timberwolf

Quote
The Canadian Forces use a Leupold Mark 4 16x40mm LR/T M1...

Last edited by sir_springer; 04/12/14.