Sig Sauer has such an outstanding and well-earned reputation for top-quality firearms, some people would be surprised to discover the company added thermals to its portfolio several years ago.
Under its Optics division, Sig offers a single thermal clip-on, three monoculars and several weapon sights. Recently, I ran one of Sig’s newest unit’s, the ECHO RQ35 thermal scope — my first experience with Sig thermals.
At its price point, the ECHO RQ35 will very much appeal to the first-timer thermal buyer who isn’t ready to invest $3,000 and up. Yet, the ECHO RQ35’s functionality and features are much better than “entry level.”
Long Run
Featuring a 35mm objective lens, the ECHO RQ35 boasts 384x288 thermal resolution, 12um pixel size, and a 50Hz refresh rate. Sig rates the unit’s thermal sensitivity at less than 20mK.
Sig also lists the ECHO RQ35 with a 12-hour runtime. Long-time thermal users will remember a pair of CR123 batteries running their thermal for maybe four hours on a good night, with several extra CR123s in pocket.
How did Sig get 12 hours out of the ECHO RQ35? It starts with the unit’s rechargeable internal battery. The battery recharges through the USB-C port on the right side of the scope tube. Simply rotate the turret’s cap 180 degrees to expose the USB-C port, and plug in a charger.
The thermal also uses a replaceable and rechargeable 18500 lithium ion battery, which fits into a compartment on the opposite side of the USB-C port. Sig includes two of the 18500’s with the ECHO, plus a battery charger and the necessary USB-C-to-USB-C charging cable.
In the field, a hunter can remove the 18500 battery and replace it with a fresh 18500 without turning off the thermal or affecting the internal battery’s operation.
Sig’ s MOTAC or standby auto-shutdown feature also conserves battery life. MOTAC allows the user to set the scope’s display to shut down after 5, 10, or 60 minutes of inactivity, with a complete unit shutdown at 30 or 60 minutes of no activity. The MOTAC setting is configured through the menu system.
The thermal offers the users eight different palette options, six reticle choices and five different reticle colors, as well as the various image adjustments and enhancements standard on most thermals (contrast, brightness, etc.). Picture-in-picture is an option, too.
Digital zoom of 3.5x to 28x is built into the unit; magnification is increased/decreased by simply turning the magnification/menu ring located just ahead of the scope’s menu button.
The ECHO offers a unique on/off control set up, with the power knob located where a traditional scope’s elevation turret is found. The control employs three settings: Off, turned all the way to the left hash mark, On, the center mark, and Standby with the far right hash.
The thermal also takes photos and video with audio by using the red button atop the scope’s end section. The thermal does not have an internal gallery for viewing media, though it does contain 32 GB of internal media storage.
Sig designed its ECHO line for long range shooters and hunters and to that end embedded the units with ballistics calculators. To access this function, the ECHO user downloads the Sig Ballistic App (SIG BDX) onto a mobile device and synchronizes the app with the thermal.
The ECHO RQ35 is large, measuring out at nearly 15 inches and weighing 31 ounces. It fit well on my test rifle (see below) but might not be a great choice for rifles without ample rail space atop the receiver.
Sig on Sig
I mounted the ECHO onto a SIG516 G3 AR rifle. I reviewed the 516 G3 in the May/June 2026 issue of SSR’s sister publication, Tactical Retailer, and knew it was reliable and extremely accurate. Chambered in 5.56 NATO, the SIG516 G3 features a 16-inch cold-hammer-forged barrel and a 1:7-inch twist rate. The rifle operates on a short-stroke piston system.
Other features include a free-floating handguard with M-LOK slots, fully ambidextrous controls, a match trigger and steel reinforcements on high-wear parts of the upper receiver’s cam path and feed ramp.
Mounting the ECHO was extremely easy as the unit sells with two Sig 30mm ALPHA6 rings. The rings fit right onto the 516 G3’s rail and their 1.5-inch height puts the thermal at the perfect level for my right eye.
Good Groups
At my outdoor range during a June morning, I zeroed the ECHO RQ35 at 50 yards. I used Remington UMC .223 Rem ammunition loaded with 55 grain full-metal jacketed bullets.
My first shots hit low and left, one striking the edge of the cardboard backing of my target, the other two hitting just off the cardboard as the dirt berm behind my target revealed.
I pressed the menu button and scrolled to the reticle setting. Within that, I selected the zero function. The zero is a one-shot system, and I first selected the horizontal option, and moved the red zeroing reticle to the left to the approximate area of my first shots. I then did the same procedure for the vertical setting and saved these changes.
My next shots hit at the lower left corner of my target, a small heat pack with an overlay of black duct tape.
I re-zeroed using the one shot function, saved these changes and fired three times. Right into the middle of my target.
At the 100-yard lane, my initial shots impacted a couple inches high. Time for a slight re-zeroing.
I ended up shooting three shot groups of 1.25, 1.1 and .85 inches. A pair of five-shot groups came in at 1.4 and 1.1 inches.
I was sold!
I shot during the day, a cloudy one, 69 degrees with 69% humidity. The heat packs and pieces of black tape I used as my heat sources showed up, though not as well as I would’ve liked.
They would, I suspected, show up even better at night, which I proved to myself a couple evenings later.
Easy Targets
In my local countryside a few nights later, I scanned with the ECHO RQ35 from a small hill.
Nighttime images certainly popped with more intensity than they had during daylight. Outlines of deer and other animals were sharp-edged out to 200 yards or so. After that, the edges became increasingly blurry.
One thing I noted throughout my night evaluation was that, even close up, the heat signatures showed little detail within the outlines of those heat signatures.
Yes, the deer I spotted would’ve been easy (though obviously illegal) targets out to 200 or 300 yards, so I’m sure hogs would be, too. But whereas other thermals I’ve used in the field built with the same-sized sensors would reveal hotspots like the extra heat radiating from the heart/lung region of the deer, it was as if the ECHO RQ35 heat signatures were so strong, no inner details could be seen.
I switched out palettes and adjusted brightness, contrast and sharpness, but the details within the outlines eluded me.
The thermal has one feature that will really help the night hunter new to the unit. It’s labeled as the “Button Description” within the menu. This is a diagram of the unit’s controls with an explanation of what each control will do if quick-pressed or held down. The diagram shows up in the display.
Nice touch, as it is easy to forget what button does what while hunting in the middle of the night with starlight your only illumination.
I took many photographs and videos with the ECHO that night and they came out quite well. Accessing media requires downloading the Sig BDX App onto a smartphone, and I did just that, downloading the app and then retrieving the media.
Easy.
True Opportunity
Actually letting customers handle and look through a thermal is a key to generating sales. But Troy Hellman, Sig’s director of marketing, Optics, finds a good number of retailers missing their true opportunity here.
“It’s incredibly simple to make it work, but I see this single problem frequently,” Hellman said. “You need to ensure that the device settings are optimized for the environment in which it will be used. When focus, contrast, brightness, magnification, etc. are out of whack? It can create a poor first experience for the consumer that walks up and asks to see a device. This is particularly critical with thermal.”
Once the customer has seen what the thermal images look like and tried out a menu function or two, Hellman thought sales staff would do well to stress three points about the ECHO RQ.
--The unit’s under 20mK thermal sensitivity.
--The long battery life, up to 12 hours, and that the thermal ships with two batteries.
--The ECHO RQ35 is covered by the “Infinite Guarantee,” Sig Sauer’s Lifetime Warranty.
“There isn’t another company on the market offering a lifetime warranty on thermal,” Hellman noted.
Sig does its part aid dealers, too.
“Broadly speaking, Sig dealers have access to a wide variety of physical and digital materials to support awareness and education for Sig products, Hellman noted. “These materials can be accessed easily through the local sales rep and our digital portal, respectively. For the ECHO thermal line specifically, Sig has produced countertop locking cases, signage, in-store video assets, and brochures.”
Sig also fields a dedicated team of Sales Trainers who cover the country providing top quality in-person training and events.
“Relative to the size of a specific account, co-op ad funding is available and encouraged,” Hellman added. “SIG Rewards is our flagship sales staff incentive program. We also participate in various third-party training/sales incentive platforms.”
Infinite Guarantee
Independent FFLs can’t purchase directly from Sig Sauer, which uses a solid distributor network to provide the entire line of Sig Electro Optics to retailers.
Sig distributors include AmChar Wholesale, Inc., Chattanooga Shooting Supply, Crow Wholesale, Davidson's, Iron Valley, Lipsey's, Orion Wholesale, RSR Group, Sports South and Zanders.
“If a prospective dealer/retailer is interested in selling Sig Sauer product, they will contact our Customer Service team via phone or email to be connected with their local sales representative,” said Hellman.
Reach Sig customer service at 603-610-3000, option 1, from 8:30 a.m. to 5:00 p.m. EST.
Prospective dealers can also submit an online request at www.sigsauer.com/customer-service-contact.
Sig thermals have earned numerous reviews across the digital landscape. Sales staff yet to experience Sig sales team training can help themselves by examining these reviews.
“Our ultimate goal with the ECHO line of thermals was to alleviate some of the most common friction points in thermal user experience,” Hellman explained. “How do we keep the user in the field longer? Improve battery life, give them an extra set in the box, and build the thermal with a rechargeable internal battery. How do we ensure that the device is easy to navigate? Design the user interface/user experience software in-house with shooters, for shooters.”
He concluded, “And how do we show the customer that we believe in our device? We back it with our Infinite Guarantee, no questions and the thermals covered for life.”
