The non-circular, relief cut objective lenses is a problem which thinks it’s a solution looking for a problem.
1) Exit pupil & image brightness: One easy answer to “why is it bad?” is found by asking yourself, why do shooters use larger objective optics in the first place? So let’s run that rabbit trail for a second, shall we? Field of view is one reason - but that’s easy to get, run less magnification. So why? Well, because a particular application needs more magnification - so we run larger objectives to improve not only field of view, but the more important reason is exit pupil. The human pupil has a typical span of 2-7mm, with strain and some change or loss of focus quality across that span - as might be expected, that span will typically reduce as eyes age. Any time the exit pupil of your optic is too small, the image gets dark. You can see this in these 6-24x40mm optics, where the image appears to be the same bright, high quality image until you hit a certain zoom setting and it suddenly starts to darken. Why? Because there’s more and more light coming from around the scope, entering the pupil, as compared to the intensity of light coming from the scope. Jump up to a 50 or 56mm objective and you won’t see that same dramatic darkening with zoom. In the context of these asymmetric Leupold VX-L’s, the “bite out of the cookie” is robbing light from the optic. So even though they have a large diameter, they don’t have as much light entering the optic and subsequently reaching the shooter’s eye. You don’t see that marked transition in brightness with zoom change, but side by side with a non-L scope, they’re not as bright (notably for me), and considering Leupolds aren’t famously bright already, it’s a problem.
2) Does it solve a real problem? - Impact of being closer bore axis on MPBR (aka, the main selling point for this design): we talk all of the time about how important it is to have our optic axis close to the bore axis, but have you ever questioned how much difference it really makes? I ran the numbers on a 5” MPBR just now - if I dropped my 2.2” scope height on my 6 Creed by 1/2” (mind you that would be a 12mm bite out of a 50mm optic), it changes my MPBR by 8 yards... Your optic height goes into your calculator, and we’ve had ballistic calculators for FREE for over 20yrs - that offset is factored into your drop data, and never bothers a shooter, ever. Some of the most accurate rifles in the world are benchmounted rigs, no stocks, which have the optic mounted WAY off of the bore, not even on top of the rifle. Height over bore is largely irrelevant. You simply need to know the height, and gain virtually nothing by shrinking that difference by 1/2”.
3) Cheekweld: Cheekweld is Cheekweld - not all stocks offer an optic height which fit all shooters, and lowering the scope doesn’t change that. For example, any rifle which fits me has my wife struggling to crawl down into the scope, and anything which fits my wife has me struggling to reach up to it. My cheekbone to my eye is very short, so every rifle I own needs a cheek riser. In the past, many more stocks were designed with comb drop to allow iron sights, but most rifles in the last decade are built without irons, and the combs aren’t as low. Lowering scopes might mean older stocks don’t have to reach up as far, but I’d much rather install a proper fitting stock, or a $25 cheek riser than carve a slice out of my expensive optic and sacrifice the light gathering quality I mentioned above.
4) Optic size: dropping the scope even a half inch doesn’t really change much in terms of the major dimensions of the optic, let alone the rifle. A 50mm with a bite wound is still ~60mm diameter, and that bulky side to side. It’s just as long as a standard full circumference optic as well. It just gets to set 1/4”-1/2” lower to the barrel.
5) Real world fit: for several of my sporting rifles, the bolt handle and ocular bell diameter (or power ring diameter) dictate how low my scope can be mounted. Doesn’t matter how big the objective bell might be. On most of my rifles, I am using low or medium rings already. So what space are we really taking back?
6) Distortion: no way around it, the more oddly you shape the lense, the more odd things it will do to your light passing through the optic. Edge effects are one reason you rarely see true 1x optics - light which passed through the edge bevel of your glass does wonky things, so manufacturers zoom slightly so the shooter never actually sees through the edge of the glass. But when you take a substantial bite out of the profile, you’re either throwing distorted image up into the shooter view, OR, you’re throwing a mechanical limiter into the mix so the shooter never sees the bottom edge... Equally, the concave outer profile of the objective bell is a convex internal surface. Despite best efforts to matte black the internals to eliminate internal diffusion, a convex surface diffuses light much more so than a convex surface - overall pulling your image quality down.
7) Mechanical limits vs. image vs. hold over: if you design a scope with a bite wound, but don’t want your shooter to SEE the negative edge effects or the edge profile in the scope, you mechanically limit the erector tube travel to not face the bite. But if you do that, why are you buying that much objective diameter in the first place? Why buy a full diameter, full weight optic which has a limited erector tube travel to never use the full diameter of the objective lense? How much image are you missing which was “seen” by the corners, but not by the shooter? How much elevation capacity are you losing? How much hold over opportunity would you be losing if they removed the mechanical limiter and let you see the bite?
Again - mechanically, these scopes are a problem disguised as an answer to a problem nobody was really asking to solve. Certainly not at the cost of the compromises they bring with it. It’s like the doctor asked you at your annual physical if you had any pain, and you mentioned your left knee kinda hurts when you kneel for too long. So the doctor suggests you cut off your leg and use a prosthetic - because afterall, your knee won’t hurt from kneeling any more if you don’t have a knee.
So in short - asymmetric optics are “rare for good reason”...
