Review: ATN ThOR 4 640 2.5-25X

If you’re a hunter after predators and pests, you understand the need for good thermal. Without a thermal scope, lights are your only option — if legal where you live. That’s not necessarily effective anyway since it can, and will, scare off your target. There’s a variety of thermal scopes on the market, and we’ve used a lot of them. For this review, we put the ATN ThOR-4 640 2.5-25X through its paces, even trying out daytime use. Here’s why we think this thermal riflescope is a valid option for hunters, ranchers, and anyone else who needs to identify targets at night.

atn thermal
The thermal is rugged, reliable, and easy to use. (Photo credit: Kat Stevens)

What’s the ATN ThOR-4 640 2.5-25X?

The ATN ThOR-4 640 2.5-25X is the fourth generation of the company’s line of thermal sensor optics. Over the years, ATN has definitely grown with technological advances and improved their scopes. The proof is in this scope (and in comparison to prior generations). This thermal scope offers a host of useful features enabling the user to record hunts, zoom in, and choose the image’s appearance. The ATN ThOR-4 640 is also user friendly, unlike some thermals that are quite a challenge to figure out.

color mode on thermal scope
The thermal offers a variety of display options including the pictured color mode. (Photo credit: ATN)

What are the features of the ATN ThOR-4 640 2.5-25X?

This is a feature-rich thermal, but we’ll hit the highlights here. The scope utilizes the manufacturer’s Obsidian IV Dual Core for superior overall performance and has a sensitive Gen 4 60Hz sensor. Controls are more tactile than previous generations, meaning you can feel the adjustments made. The scope is compatible with 30mm rings, which makes it pretty straightforward for mounting it to a rifle.

When mounted to a rifle, the left dial adjusts the image’s zoom. The eyepiece ring rotates for clarity adjustments. On the center top of the scope, a series of buttons allows the user to access various functions. This includes a power button, left and right facing arrows so you can control the cursor in the screen, and an “OK” button used to confirm your selection. The raised buttons are in a basic circular layout with recognizable shapes. You can readily feel them out without raising your head and looking at them during use.

This model’s upgraded video capabilities include dual streaming with HD resolution. Videos can be recorded to an SD card for easy viewing on a laptop or other compatible device. Streaming is in 720p. If you’re worried about missing the moment, don’t. This model has Recoil Activated Video (RAV). Simply activate the RAV feature and the core will record the moment you take your shot. Options for contrasting display colors include Black Hot, White Hot, and Color.

As for the battery life, the ATN ThOR-4 640 has a long-lasting charge thanks to its core. The Dual Core Processor runs fast and cool with around a 16 hour or more battery life. It charges via an included cord; so when it’s time for a charge, you plug the cord into the side of the scope and let it do its thing. This is a much simpler method than swapping out lithium batteries or worrying about battery packs.

ATN Thor 4 controls
Controls on the scope are easy to operate, even without looking. (Photo credit: Kat Stevens)

How do you zero the ATN ThOR-4 640 2.5-25X?

This thermal scope has a one shot zero feature that actually works. All you do is take your shot, stay on target, and adjust the reticle so it’s centered over the shot you just took. It really is that easy.

How does it work at night?

For the review, I mounted the thermal to my Remington R25 GII in .308 Winchester, mostly because it’s a fantastic caliber for feral hogs. The scope was easy to mount to the Picatinny rail using the included scope rings. The rings attached securely. There’s no wiggle or slipping; the thermal is solid as a rock. According to ATN, this scope can manage significant recoil, but they mention no specific caliber. So, while I considered using this on a big bore, I opted not to take the chance.

Zeroing really did take a single shot. When I zero thermals I usually stick a hot hands warmer to a target, but there are plenty of good ways to visualize the target for zeroing. I confirmed zero with a few more shots and when they produced a nice, tight group at 100 yards; I felt confident taking the setup hunting.

The scope’s controls are great because they’re simple and easy to operate without stopping to watch what you’re doing. The magnification works with impressive smoothness and gives you the option of a broad field of view or zooming in on a target. Of the three display settings, White Hot was my favorite because it offered the greatest clarity for my eyes. This might be due to how the area I most often hog hunt at night is laid out. The area is hundreds of acres of open fields ringed by trees. This setting seemed to work best for visualizing and identifying animals.

At 100 yards, animals are easy to identify. I had no trouble telling the difference between deer, hogs, raccoons, and rabbits. In fact, I even picked out field mice running among the rows in the field. The mice just showed up as tiny dots, of course, but it was great clearly seeing them run around. There’s no issue with glitching or buffering, so you can scout a field and watch animals without worrying about suddenly losing the field of vision.

For me personally, there’s a definite adjustment period for my eyes coming off and on thermal. This means I try to limit how long I stare through thermal scopes without raising my head and looking elsewhere for awhile. How long you can handle looking through thermal without any vision disturbances when you raise your head really depends on the user. Generally speaking, the longer you look through thermal, the more time it’s going to take your eye to readjust to ambient light.

I’ve used this thermal to take a single shot on a hog or raccoon and also to drop multiple hogs in a row when entire sounders are out tearing up the fields. Target acquisition is great, there are no issues with smoothly panning to the next target for a shot. Years ago, this wasn’t true for early thermal generations. Thermal really has come a long way.

On the downside, as with any thermal, you start losing clarity if it’s misting, rainy, or there’s a heavy fog. Thermal is never a big fan of heavy moisture in the air. Even so, in the mist and fog this thermal provided enough clarity to continue hog hunting.

thermal eyepiece
A rubber eyepiece helps protect your eye and provides a better, clearer view of the screen. (Photo credit: Kat Stevens)

How does it work during the day?

During daylight hours, the image is brighter with fewer sharp contrasts but still functions just fine. If you’re scouting for deer during legal light, keep in mind buck antlers can be hard to see due to lack of heat. If the buck lifts or turns his head in just the right way, you can get flashes of the rack size and points; but it’s iffy. For that reason, it’s wise to have a good set of binoculars as well for identifying shooter bucks. It’s legal in most states to use a day/night thermal for deer hunting during legal shooting light, but make sure to check the laws and regulations in your area just in case. And remember to stick to shooting light. Don’t let the existence of thermal capabilities convince you to fudge when you take a shot.

Should you get the ATN ThOR-4 640 2.5-25X?

This is a great thermal scope that’s a bit more affordable than some. It’s durable and rugged, and the battery life really is impressive. In addition, thanks to the included USB-compatible cord, you can charge it while in your vehicle. Clarity is good, target acquisition for follow up shots is smooth, and magnification capabilities are clean. Even out to about 400 yards, I was able to identify a bobcat after watching it move for a moment. If you want a good thermal riflescope, this model is a great option. ATN’s fourth generation is well-made and reliable. Furthermore, this scope has done a lot to clean up the feral hog population here. It’s well worth the investment. The ATN ThOR-4 640 2.5-25x is available at GunMagWarehouse for $3,699.99.

Kat Ainsworth Stevens is a long-time outdoor writer, official OGC (Original Gun Cognoscenti), and author of Handgun Hunting: a Comprehensive Guide to Choosing and Using the Right Firearms for Big and Small Game. Der Teufel Katze has written for a number of industry publications (print and online) and edited some of the others, so chances are you've seen or read her work before, somewhere. A woman of eclectic background and habits, Kat has been carrying concealed for over two decades, used to be a farrier, and worked for a long time in emergency veterinary medicine. She prefers big bores, enjoys K9 Search & Rescue, and has a Master's Degree in Pitiless Snarkastic Delivery.

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