Field Test: Burris BTC35 V3

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When we factor in the cost of going thermal, some of us go ahead and add in the price of a new rifle, too. Although it doesn’t take a lot of effort to remove and remount a couple optics when switching from a traditional riflescope to a thermal unit and back again, most of us would rather leave them alone so that we don’t have to zero them again.

An efficient alternative comes in the form of the Burris Thermal Clip-on, or BTC, which clips onto the existing optic’s objective bell and can be removed in seconds without substantially altering point of impact. The BTC35 is now in its third generation and boasts more features than ever before. When it’s off the rifle, a rubber eye cup is included to use it as a handheld scanner. With the addition of a bottom mount (sold separately) it attaches directly to a rifle as a standalone optic using the reticle feature.

If you’re new to thermal technology, let’s start with a little 101. Thermal imaging is essentially a computer-generated picture built from the temperature differences the device detects. Some compare it to night vision, but it works very differently. Whereas night vision amplifies existing light, thermal imaging works in all light conditions, including broad daylight. Thermal also has the advantage of “seeing” through thin obstructions and illuminates living objects far more brilliantly.

As with any electronic device, comprehending the specifications will help you understand what you are buying. Thermal geeks can digest every value on a couple spec sheets and then debate for hours (usually over the Internet) about which optic is better. As an instructor, I tell my students to focus on just two stats: pixel pitch (sometimes referred to as size) and sensor resolution. Sensor resolution is straightforward: the higher the numbers, the greater the detail. It is much like buying a TV. Pixel pitch is the opposite. The lower the number, the better the image. Compared to the rest of the Burris thermal line, the BTC35 V3 sits toward the middle for image quality. However, as far as utility is concerned, it resides at the top.

The BTC35 V3 comes with a charging cable and a pair of rechargeable batteries. The unit has compartments for two batteries but can run off just one, allowing you to swap batteries as one becomes low without having to power down. On a full charge, you can expect about two hours of run time, but this is extended through the auto standby mode. This can be set to kick in between 5 and 15 minutes (or not at all). I liked using it, as flicking the dial or even twisting the focus ring wakes it up in an instant.

One thing you won’t find in the box is a mount, as Burris offers 10 Smartclip adaptors of different sizes to clamp it to a scope’s objective, plus a Picatinny rail mount if space allows. The Picatinny mount is the same one you need to use the BTC35 V3 as a standalone optic. I chose a Uintah UP-15 as my test firearm, which has a Burris RT-6 1-6x24 mm scope on it. I consider this my all-purpose rifle, as I might be hunting foxes with it one day then banging steel with it the next. After using the appropriate Smartclip to snap it onto the front end of the optic, I was ready to get started.

I began by scrolling through the menu via the button on the left side of the optic before reading the instructions. I did this to get a feel for how intuitive the BTC35 V3 is to operate, as memorizing a manual is low on my list of fun. Pressing the button inward is the “enter” key, and turning it scrolls through the menus. In the main menu, I found the option for screen adjustment and was able to center the image within my riflescope. Centering is going to be different for every scope, so Burris allows you to save settings for three scopes if you plan on bouncing around. Color palette selection is also included in this menu; there are nine options. I left sensitivity at the factory setting and chose white-hot as my palette, as I like the background dark and targets bright. The main menu is also where you’ll find general display, thermal and operational settings.

Backing out of all the menus, I spun the dial and found that it cycled through the 1X, 2X and 4X zoom settings without having to access any menus at all. This is an important feature to remember, as zoom adjustments typically need to happen immediately. Although the dial was fast, I found that zooming with the riflescope yielded better clarity, so maybe it’s better to save the digital zoom for when using the BTC35 V3 by itself.

Taking it to the field, I sat quietly with the rifle in one hand and a rangefinder in another. Observing some blackbirds in the distance, I found that the thermal was able to pick them up in the grass as far out as 153 yards. Being that the field was in full sun on this 85-degree day, I was impressed. Clarity and detection only get better when the ground cools, so there should be no trouble addressing larger animals like hogs and coyotes within 300 yards in cool temperatures.

I took the setup to the range for a zero check and durability test. I began by unclipping the thermal and punching a half-MOA group at 100 yards. After reattaching the thermal and firing another group, I found that point of impact shifted 2 1/4 inches downward, but group size remained relatively the same. Impressed with the group, I cut the scope some slack for the shift. Adding tension to a scope, not to mention an additional set of lenses, will naturally change things.

To remedy this, simply remember to correct the scope by the discovered amount after clipping on the thermal. Better still, just split the difference and make that the new zero. I took the latter route and settled on a zero that was around an inch high with the scope alone and around an inch low with the BTC35 V3 mounted to it. That’s not enough to matter on even something as small as a raccoon, so I called it good. I finished my testing by ensuring that a magnification change didn’t affect anything. I fired a three-shot group at 1X and a three-shot group at 6X; it passed.

The Burris BTC35 V3 kept its promise and offered the utility of a thermal without having to dedicate a rifle to this technology. I found the image-quality-to-price ratio to be appropriate and the menu to be uncomplicated to navigate. I appreciated the fact that the unit comes with a rail section to give you back some of what might be covered up by its installation. This is also a great place to mount an external battery pack should you feel your hunt is going to run into overtime. The BTC35 V3 makes a great addition to a multipurpose firearm, varmint gun or even a general plinker. The best part about this thermal is that it can go on all three, and there is value in that alone.

SPECIFICATIONS: Burris BTC35 V3

Sensor Resolution: 400x300 pixels

Pixel Pitch: 12 microns

Frame Rate: 50 Hz

Optical Zoom: 3.2X

Digital Zoom: 1X, 2X, 4X

Screen Size: 1024x768 pixels

Power Source: 2 RCR123 rechargeable batteries

Runtime: 2 hours

Length: 5.9"

Width: 2.9"

Weight: 16.2 oz.

MSRP: $3,000

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• This article was featured in the December/January 2025 issue of Game & Fish magazine. Click to subscribe.

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