Wow, what a firestorm. Sorry for the delay in coming back; work is a bear.
What ILya said about deducing the thickness of the wall by only looking at the adjustment range being unadulterated nonsense is very correct. But I was correct; the Zeiss has a 2mm thick wall. The usual wall thickness for aluminum riflescopes is right around 2mm, so it was an easy guess. I used the adjustment range to confirm in my mind that Zeiss did not have a thicker wall.
In my experience, the difference between a 1-inch (25.4mm) scope and a 30mm scope is the wider adjustment range of the 30mm. The difference between a 30mm tube and a 34-36mm is one of two things: larger adjustment range or thicker wall. This is for equivalent styles of riflescopes, of course. I went looking at Nightforce and they state: "They are two to three times thicker than other riflescopes. This means less overall stress, greater thermal stability, a consistent zero and a virtually impervious shield for the precision optics within." Their ATACR series has an adjustment range that leads me to believe it indeed has a thick wall. (Happy to be corrected.)
I went looking at the Tangent Theta site and looking at the specs of their 34mm tubed riflescope, I believe it has a thicker wall. (Happy to be corrected.)
I went looking at the ZCO site and they have 36mm tubes but with ordinary adjustment range. I believe those have thicker walls also. (And also happy to be corrected.)
The short riflescopes will have a larger adjustment range compared to the conventional riflescopes and, of course, there are always variations and exotics and so on. In our case here we are comparing a March-FX 4.5-28X52 to a Zeiss LRP S3 4-25X50. The zoom ratio is virtually identical (6.22 Vs 6.25). The eyepiece diameter is almost identical (46mm Vs 45mm). The objective lens is similar (52mm Vs 50mm). The length is similar (12.5in Vs 13.4 in and I notice the objective lens on the Zeiss seems to be deeper in the objective bell.) These two riflescopes are very similar in every respect, except that the 34mm-tubed March has 30MIL of elevation and the 34mm-tubed Zeiss has 46.5MIL.)
So now, I revealed a new metric that seemingly none of you were aware of, and panic ensued. I NEVER said that 2mm thick tubes were bad. They are perfectly fine, and they work very well. But as pointed out earlier, some manufacturers opt for thicker tubes for various reasons. This extra thickness does not extend all the way to the front of the scope, you would notice the extra 4mm of objective diameter compared to other riflescopes.
The extra thickness of the main tube is a little bit like the extra thickness of a rifle barrel. As Nightforce explained it provides for greater thermal stability, among other things. That's pretty important to me, especially when I shoot at places like Ben Avery, Raton, Bayou and other hot, sunny venues. And it protects the internal precision optics even better. I can vouch for that; I still remember that incident with my match rifle a few years bag; I thought I was going to have an episode when I heard the sickening crashof the rifle hitting the floor on the riflescope. The next morning at the 1000 yards match, I could not detect any difference.
Some manufacturers such as Nightforce use 6061 aluminum, others use different aluminums. I don't think that makes any difference in the performance of a riflescope. It would be interesting to see what aluminum is used by the various manufacturers, but I believe many treat that information as proprietary.
Finally, let we just add a few thoughts about adjustment range. I'm an F-class shooter (boo, hiss.) I usually compete at 1000yards. I have setup my riflescope such that at 1000 yards, it is just slightly above mechanical 0; the optical path sweet spot. This is where a riflescope will provide the best IQ. When I pay over $3000 for a riflescope, I want to enjoy the very best IQ I can extract from it and that's as close to the middle as possible. My March-FX 4.5-28X52 is mounted using a 20MOA rail. I do everything I can to stay away from the extremes in adjustment.