First of all, MPVO/LPVO/HPVO etc are just terms used within the industry. Most of us would understand that a Low Powered Variable Optic (LPVO) in today's standard would start at 1x on the magnification ring and provide a true 1x - both eyes open experience to the user that includes a reticle that works for quick acquisition at 1x. So, if you ask practically anyone with knowledge in the shooting world "what is a good LPVO" you will get answers for optics that all start at 1x. This definition makes it pretty easy for manufactures to satisfy the market. However, with a Medium Powered Variable Optic things start to get a little fuzzy, just like the responses above indicate. This is why myself and many others have tried to better define or narrow down the definition rather so manufacturers get a better understanding of what we're asking for. For the most part, this is a First Focal Plane (FFP) world, so we'll leave the plethora of SFP scopes out of the equation (they have their place but not here as an MPVO candidate).
For years we've had 3-9's, then 3-12's and 4-16's, then the 5x erectors came along and gave us 3-15's and 4-20's and 6x erectors gave us 2.5-15's and 3-18's et al, I'll stop there for now. And now we're starting to get the 2-10's and 2-12's, but something is lacking as in the example of the Steiner H6Xi 2-12x42 and that's the reticle, even Leupold struggled before the CMR-Mil became available quite a while after the introduction of their Mark 5HD 2-10x30. So, it's not so much that we have a lack of viable optical designs that "could" work as an MPVO, we have a lack of manufacturers understanding the type of reticle that makes an MPVO usable. By and large, the answer has been staring them in the face - put your LPVO reticle in the MPVO scope, well, that is as long as it is a decent LPVO reticle like NF's FC-DMx mil - I have often advocated for NF to offer this reticle in the NX8 2.5-20x50 scope, even better if NF introduced a 1.5-12x42 in the NX8 line but I digress.
The point is, the primary use case of an MPVO is to be put on a semi-automatic gas operated rifle which is one of the most popular sporting rifles in the USA today. Many gas gun shooters have now recognized the limitations of the LPVO especially for longer distance work and even our SF operators have recognized the benefits of piggybacking an RDS on top of their LPVO's so the natural progression indicates something slightly higher powered than an LPVO that is designed to excel optically at the higher magnification rather than at the bottom but it has to have a reticle that is effective at the bottom magnification.
So, when you ask, can a 4-16x42 be considered an MPVO I would generally say no due to the reticle and the length of the scope. Granted, I think the NF ATACR 4-16x42 is one of the best mid magnification optics on the market today for gas gun shooters wanting to reach out and touch some steel at distance, but the reticle is not designed for low magnification work and so it struggles in that area. I also think the scope is a bit too long and bottom magnification a bit too high for clip on use and so we enter yet another criteria of the MPVO - shorter body and low enough magnification for effective thermal clip ons.
If manufacturers would spend a little more time to get the reticle right there would be a lot more interest in their designs. ZCO and March have likely the best reticles for MPVO right now, but these are high dollar scopes. Athlon has had a great reticle in their Helos 2-12 though, some think it's a little too thick, and now Swamp Monkey or whatever that company is has also introduced the CCP cousin to the Helos filling the "cheap" niche for this market. We need something in that $1500 - $2k gap and also something in the $1k market that punches above its class optically, these are the two areas that have the most potential IMHO.
