You’re talking about two separate things:

Housing and tubes.

Tubes—your BNVDs can always be upgraded to newer tubes to give you better performance, any MX-10160 format tube will work just fine.

According to the manufacturer, the PVS-15 and the PVS-31 use non-standard tubes that have different specs than the standard 10160 or 11769 tubes and are not suggested to be used in other models. At the same time, there are folks who have done tube swaps and work outside of the manufacturer’s recommendations, so take that for what it is. That being said, as noted, in broad terms, the PVS-15 takes an 10160 format tube, while the PVS-31 is an 11769 format tube.

Most NVD BNVDs will have dovetail interfaces, so if you have a dovetail interface already, they will be able to use the same mounts as the PVS-15 and 31s, though if you have a bayonet mount version of the BNVD, you will need to swap mounts as well.

Optics are slightly different on all three but all optimized for ground use. Not saying there’s no difference, but most users will not likely notice much significant difference, the tube quality is still much more important here.

PVS-15s and PVS-31s can be had in several grades of tubes, you’ll find more available variety in PVS-15s, PVS-31s, it’s a much smaller list of likely candidates, but just be aware, not every “WP PVS-31A” (e.g.,) is identical, they’re built to different performance levels based on the customer/customer requested specs. State/local LE, military/federal, SOF, SMU all have different tube standards, and PVS-31s can come in green, white, filmed, unfilmed, etc.

From a performance standpoint, knowing what tubes you’re getting is the most important factor.

From a housing/human engineering/logistics standpoint:

BNVD is honestly probably the most durable of the models you’re inquiring about, and the easiest to maintain. Not only is it a “purely commercial” system that does not and never had restrictions on it, but it uses common and standard parts, and is supported by a commercial manufacturer.

The PVS-15 is honestly a dying system, it was never cheap or easy to maintain, and while there’s been a recent glut of PVS-15s and components as more and more folks transition to the PVS-31 family or the 1531s, but this will eventually dry up. A similar trend occurred a little while back with PVS-23s, though their saturation was never as high as the PVS-15, so it was a slightly smaller run on parts and components. The PVS-15 also has by far the smallest range of articulation between the three if that is important to you.

The PVS-31 will be the lightest of the three by a decent margin, but will be the most expensive/difficult to maintain, and hinge breakages are fairly common—though to be fair, most of the folks currently using them are LE/military who put a beating on their gear anyways, and they broke PVS-15s pretty regularly, too.

With the PVS-31 you’ll get variable gain and external battery capability, but you’ll lose onboard IR illumination and focusable diopters.

Of the two, the bigger “problem” is the diopter focus—if you’ve ever tweaked the eyepiece lenses of your goggles—you can’t do that with the 31s, meaning there’s a limit to how clear you can make the image. L3 does offer diopter replacement kits at $2,000-ish a pop, but they’re obviously a pretty coarse adjustment since they’re fixed values. A nice goggle for sure, but built to some very specific requirements that may not match everybody’s needs.

Of the three, IMHO, your best value would probably be to upgrade the tubes in your current BNVD, though if you really wanted to roll your current ones over, you could always just buy a new set of BNVDs, maybe the SG model if you wanted to try out the manual gain (not really my preference on binos, but that’s a different conversation)—or, if you wanted to try a new housing as well, I would recommend you look into the DTNVGs as well, since you seem pretty sold on articulating-style goggles.

~Augee

I mean, you would get way more IG likes.

~Augee

You may or may not have been hearing someone discuss the PVS-31s, part of the issue:

BNVD is sort of like “AR-15,” because depending on context:

BNVD or BNVS is a generic acronym for “Binocular Night Vision Device/System.”

On the other hand, Night Vision Devices (formerly Depot) has marketed their main bino line using BNVD as the model name, just like RNVG or Sentinel.

Meanwhile, L3 also uses BNVD to refer to the PVS-31 family, as “AN/PVS-31” is technically a military designation, all L3 part numbers for the BNVD typically begin with “BNG,” and when you order them, you order “BNVD” on the PO.

Finally, FLIR also builds and markets a google that they too call the BNVD, available in both 40 and 51 degree models with Gen. 2 and 3 tubes.

If you were hearing someone discuss the durability differences between the PVS-15 and the BNVD, there’s a good chance they were referring to the L3 BNVD.

The NVD BNVDs are a very durable system and are machined from Delrin, the same material used in the Sentinel and MOD-3B for many of the components.

~Augee

This is counter to anything I've heard before (NVD BNVD v. PVS-15), though I can't say I know of a scientific "torture test" having been done comparing them, either, but it sounds like someone who has had a bad experience with a BNVD (they all break if you beat on 'em hard enough ) or someone who's trying to sell you a PVS-15.

The FLIR BNVDs are carryovers from the Armasight acquisition, so they're "Armasight by FLIR BNVDs." That's neither good nor bad in and of itself, and I'll admit to not having a super lot of hands on time with them, but at the end of the day, the standard 40^o FOV units don't really offer much of anything that other, more proven BNVD units don't, along with a healthy dose of proprietary parts, and the 51^o FOV technology... simply isn't mature IMHO. I've looked through various different "WFOV" and "foveated" systems, and none of them have really made me want to trade in my 40^os. I think there's promise in the concept eventually, but it's just not there yet.

~Augee

+1 on this. I use the gain mainly to turn DOWN the brightness.

The other thing not mentioned on the BNVD- single gain is that all the controls are just like a PVS14 so if you are coming over from a PVS14 it's all pretty much the same function. Nothing new to learn or forget under stress.

My son and I were doing some shooting last night and I found myself leaving the right tube focused in for checking the target, then rolling it up to the side to shut it off and walking back to shoot and shooting with just the left and then rolling the right down (focused in close) to check the targets  out of habit and laziness ;)

Different people's eyes have different sensitivities to brightness, and frankly, people just plain like different things.

Ultimately, IMHO, most people mis-use and overthink the manual gain controls on their goggles, and it ends up being counter-productive to what BNVDs allow you to do.

The ABC (Automatic Brightness Control) IMHO works better and faster and more seamlessly, IMHO, than fiddling with the gain manually. While manual gain can be important in a monocular because your brain can tend to "shut off" or ignore input from one eye if it's being overwhelmed by the image from the other, so it's important to be able to "even out" the images--with a bino, your eyes are getting similar inputs from both eyes, so there's not really a need to mess with the gain to keep your brain from only paying attention to one eye and ignoring the other.

Meanwhile, the best analogy I can think of for ABC vs. manually adjustable gain is cell phone screens: granted, my experience is primarily with an iPhone, and for the most part, my iPhone screen brightness auto-adjusts based on the ambient lighting conditions, which, if you let it work, is usually very effective and seamless from environment to environment. However--I can also mess with the screen brightness manually--that doesn't necessarily mean that the phone stops auto-adjusting, but now it's also trying to respond to my inputs, which could frankly be wrong, and this frequently leads to mismatches between screen brightness and lighting conditions until the sensors sort themselves out, and/or you're forced to intervene again manually, and start messing with the gain again.

Now, consider this in context of the types of things binos allow you to do--I know that in general, we're not talking about night vision aviation in this forum, and we don't sell FAA certified aviation NVDs--however, I often bring up what pilots use and what pilots are doing with NVDs, because ultimately they're on the bleeding edge of performance, both technologically and in terms of human engineering factors--they're fast movers, have a lot of inertia, meaning they need to be able to respond to stimulus extremely quickly in order to avoid accidents. The thing is, while the consequences may be far less catastrophic, all of these things can apply to individuals running or driving on the ground as well--and what binos allow you to do among other things, is to move faster, and more [ugh] dynamically.

Aviation goggles don't have manual gain--even though aviators might deal with a lot of changes in lighting conditions, because you're more likely to screw things up fiddling with it, and you're more likely to crash into something else because you were too busy messing with your goggles than paying attention to where you're going.

If you're moving slow and deliberately and it's so dark that you can't see anything but scintillation in your goggles a) turning down the gain isn't really going to help you that much, b) it may be time to just give in and admit you need supplemental IR, or c) if you can't see shit, may as well take a short halt, flip the goggles up and give your eyes a little rest, then Charlie Mike.

IMHO, I think part of the issue is that a lot of guys spend too much time looking into their goggles, and not through their goggles--which is why I think some people get fixated on blems sometimes, but that's a different conversation, but you should be looking through (and around and under) your goggles like a red dot, again, different conversation--but I also think that is part of why guys think that monoculars are better for mixed light environments, they're getting fixated on the screen, I love binos in mixed light, because it's even more like a red dot--I can see everything and read lighting conditions and have decent peripheral and look into souls when I decide to focus on something.

..anyways, my point is, IMHO with a binocular as opposed to a monocular, you're more likely to cause yourself more problems than the problems it might solve to by having manual gain control, and now you've got one more thing you've got to worry about, fiddle with, wonder if it got left on the wrong setting, have someone crank it all the way down and next time you try to use your goggles you have a panic attack because you think they won't turn on...

Something to consider:

Most of the goggles designed for high performance use to the request of end-users, whether aviation or ground optimized, such as the AN/PVS-23 and the PNVG/GPNVG are all ABC, as are most BNVD systems.

But wait, Augee, what about the PVS-31? USSOCOM uses those!

While I've made it clear that the PVS-31s aren't necessarily my favorite system, they're still a great goggle, especially for the purposes for which they were design. However the PVS-31 requirements were ultimately derived from the same requirements generating machine that created the TA01ECOS (SU-237/PVS), ELCAN SpecterDR (SU-230/PVS), and WMX2000 VBL (MX-12393B/PVS)--that is to say, not bad pieces of equipment necessarily, but they definitely have a little bit of a "good idea fairy got involved," "designed by committee," and an "and the kitchen sink" quality to them, with odd and extraneous features like dinky little offset iron sights, etc. Compare, again, say to the GPNVG--a device with totally different organizations propelling the requirements and development, and compare those design features...

::shrug::

~Augee

I mean, it’s more complicated than “automatic.” Also, you’re talking to the guy who prefers not to use power knobs.

Yes, civilian recreational use is quite a bit different, but I’ve also been around guys spending a lot of unneeded time fiddling with the gain to react to mixed lighting.

I have a tendency towards longer than necessary answers, hahaha, but having used both manual gain and non-manual goggles and I prefer non, and if I’m using goggles with, I treat ‘em as if they’re not.

At the same time, e.g., you have guys like MrPlayer, who’s using a unique “DBNVG” as he calls it, with unicorn OASYS thermal on one side, and he uses it to even out the two images—works for him, though for most people merging thermal and I² is not really effective. Then again, there’s also a big difference between a SKEET and a Breach. I prefer the COTI/E-COTI for what I do.

~Augee

If we do a housing upgrade for someone else's device, we warranty the housing and the work, but not the tube itself (usually applies mainly to fleet upgrades from DRMO AVS-6s to another housing or something).

Hypothetically speaking, we would simply keep whatever remaining warranty on the tube if it was an in-warranty TNV unit being converted to another housing (e.g., a Sentinel to DTNVG), however we don't really do tube conversions from MX-11769 to 10160 format, not because it's impossible to do, but it can be rather delicate work, and it simply isn't cost effective for us to offer that on a regular basis in our build/repair schedule, so converting one TNV unit to another TNV unit doesn't typically happen much, as the only ABC monocular we currently offer IIRC is the MOD-3B monocular, which requires no conversion to BNVD configuration, however there are other small-batch builders that can and do do that kind of work.

Most of the time conversion work as I mentioned is simply not practical for us to do unless it's for a fleet upgrade program or something like that, so we will often refer it out, though we are sometimes able to take small conversion jobs on a case-by-case basis if we have time in our build schedule, so it's best to call or e-mail us direct for those kinds of things.

~Augee

The 31s do. The power knob and gain control is a single push button/knob that can be used to do both.

~Augee

[emphasis added -A]

If more clarity is needed—yes, all Gen. 3 tubes have ABC, even manual gain control units, which is why you can convert MX-11769s to 10160 format if you really wanted to by removing the pigtail.

That doesn’t change the fact that you’re adding another thing to get messed with or that can cause issues (while most devices are statistically very reliable, the pigtail assembly itself is actually fairly delicate) and the specs for image shift are far more generous for non-dedicates 11769 format tubes making them harder to collimate and maintain ifyou’re talking about large numbers.

You can certainly set the gain and never mess with it and have them function using ABC-only, which is typically what I do when using manual gain binos, in which case, why bother adding unnecessary and unneeded complexity when you have the choice?

Where messing with the manual gain gets guys in trouble is rapid movement in mixed light environments, where they’ve manyally set the input at a certain for (e.g., an infil) through covered and concealed (and therefore dark) routes, and then bust out into a better lighted area—and then start moving between structures or between rooms (like a living room with large windows to a dark hallway) with rapidly changing lighting conditions, where the ABC circuitry is trying to figure out what the hell to do because you decided to manually adjust the gain low when it was really dark, and is now struggling to keep up.

~Augee

Must be an older set of BNVDs?

All the newer ones have that feature as well as individually shutting off channels if a single one is rolled up to the side. I roll mine up to the side more than I flip the whole thing up. It's probably the most handy feature to me.