That's very close to what I've been led to believe. Argon is better than Nitrogen because the molecules are larger. My 6.5X32IF Minox binocular is purged with Argon. A Krypton/Argon mixture should be even better.
The important thing is if the scope actually leaks. The big difference is between the gases passing through an effective seal by osmosis (sp ?) and a seal that no longer works. That's why it's a good idea to test scopes by submerging them in warm, 140 degree water and seeing if they leak. If they leak, after 5 mins or so, then everytime the air pressure changes, air will enter or leave the scope, along with moisture. Something you don't want in a scope. E
Since moisture is larger than Nitrogen or Argon, then that doeswn't mean that the moisture can get in even if some of the Nitrogen or Argon leak out.
