AFOV is not linear so you can’t always assume that one end precludes the other. Throw your calcs on a NF ATACR 5-25 and you’ll see a big difference between 5x and 25x, same with Schmidt 5-25. Measure top or measure bottom but trying to average is not the best criteria due to different optical designs, as the poor performance of the above 5-25’s will throw off how well these scopes do after getting out of the low end of the range.
Tunneling will obviously distort the AFOV comparison on the low end. I've never looked through the NF 5-25, but just by looking at the FOV value, I'd bet it tunnels at low end just like the S&B 5-25.
Averaging the AFOV was to simplify the discussion comparing one scope to another. Bottom line, they (all models of S&B/ZCO/TT) are within a degree or so AFOV (removing skewed values)...and as usual, purchase decisions comparing Alpha models comes down to reticle and turret preferences.
This includes the TT 5-25 vs TT 7-35. Their (spec listed) AFOV is nearly identical. How were you comparing FOV between them...by using the numbers printed on the zoom ring? I'd bet that induces enough error to eliminate its use. And (per my earlier proposal) the AFOV value disparity between min and max zoom has to be explained in (as I see it) 1 of 3 ways.
1. The low end is skewed by tunneling. (easy to explain)
2. The high end mag rating is 'generous'. (5-45 and 3-20 discussion above)
3. The scope's optical physics somehow change with zoom ring changes.
Which explanation (1 and/or 2 vs 3) do we think is more likely? Not being an optics engineer (maybe Ilya can weigh in), I can't explain the likelihood of #3...but I'd bet money 1 and/or 2 is much more likely the case...particularly given that puts all models of S&B/ZCO/TT at nearly identical AFOV... mid 21 degrees.
Example: The S&B 3-20 either actually shares AFOV (~22deg) with the multitude of other S&B/ZCO/TT models and stays under the Swaro's patent value (by actually topping out at 18.5-19x) ... or it somehow improves its AFOV as you increase zoom and disregards Swaro's patent. Occam's razor applies IMO.
The US S&B 6-36 stands in that pack with the same AFOV as the rest. Europe has a wider version, but that has zero relevance to the US market since none of the other S&B/ZCO/TT models do.
The Vortex 6-36 has <2 deg difference in AFOV over the S&B 6-36...equating to 2' increase in FOV at 100y at 6x (20.5' vs 18.5')...and only 1 INCH increase at 36x. Maybe that's enough to sway some buyers.
The March 5-42 FOV does match the Euro S&B 6-36. Maybe Deon isn't afraid of US patent infringement...that's between them and Swaro lawyers. Again, however, I doubt it'll appropriate many S&B/ZCO/TT sales.
To the community in general - many might be thinking, no big deal, just back down on magnification and you'll widen your FOV, while this is true you have to realize you are also decreasing magnification.
Agree that the 'just zoom out' argument (not that I've seen it proposed) isn't valid when comparing FOV capability...though it does speak to actual use. (optics aren't lab tools, and nobody sets zoom ring to a particular number when in use...they zoom until they see what they're looking for)
The point I'm making remains... the US S&B 6-36 mirrors all other US S&B models...and ZCO models...and TT models. I've yet to see convincing data that shows otherwise. If that pushes buyers to Vortex (for the tiny increase) or March (for a little more), that's obviously up to them. More for me!
. The US gets funky about itar bu this would be incoming. 
