I recently attended a Long-Range Carbine Course hosted by The Gun Run at Dewitt’s Sporting Clays on October 26, 2024. Ellis, the owner of The Gun Run, was the lead trainer and offered a top-notch experience with realistic targets and ranges well-suited for modern sporting rifles. The course brought out the best in our equipment and skills, challenging each student to master precision.
Many people used the Primary Arms SLx MicroPrism with ACSS Aurora Reticle as their most popular optic, especially in the 3x and 5x versions.
The Primary Arms SLx MicroPrism with ACSS Aurora Reticle performed exceptionally well across a range of calibers, from 5.56mm to 7.62x39mm, making it ideal for intermediate-range engagements and helping to create more precise shots—most of these reticles were of the BDC type and not the MOA or MIL scale.The fixed power and the ACSS Aurora Reticle are a more modern version of the Trijicon ACOG in many ways. The ACOG is the grandfather of many quality optics and is, at this point, a 25-plus-year-old design. The Primary Arms SLx MicroPrism takes all the greatness of the ACOG and adds a few more touches to make a great optic.
Sight-In Precision with the Primary Arms SLx MicroPrism ACSS Aurora Reticle
At the end of the class, I was asked about other options for sight-ins. Most of the students did a short-range zero or a 100-yard zero. What needed to be clarified in this brief time was how that process was accomplished. I wanted to emphasize to the students the importance of selecting the right sight-in distance when using a BDC (Bullet Drop Compensating) reticle. But we did not have enough time and thats why I wanted to write this blog post.
This critical step, "selecting the right sight-in distance," is often overlooked and can greatly enhance long-range accuracy. If you have access to a range beyond 100 yards—such as up to a 300-yard range—you can fully utilize the precision capabilities of the Primary Arms SLx MicroPrism ACSS Aurora Reticle.
To get the most out of this BDC reticle, we must pick an anchor sight-in distance that suits both the rifle and ammunition. For this setup, 200 yards was our sweet spot. Here’s why:
- The 7.62x39 ammo we used isn’t top-of-the-line match grade, so we’re looking at about 3 MOA accuracy from it.
- Our rifle, with a 10.5” upper, offers around 2 MOA precision.
When we add up the rifle’s and ammunition’s limits, we get about 5 MOA. At 300 yards, this results in a shot spread of 15.7 inches—plenty wide enough to hit a human-sized target consistently, as long as our aim is true.
I went to the Hornady Ballistic App and chose the G1 BC data. Also, we are not doing any super-sniper activity here; the atmospherics as set on the app are fine. Knowing the velocity of your specific ammo and some basic rifle setup measurements, you can achieve an optimized sight-in for intermediate-range precision.
Sight-In Process for a BDC Optic
To get started with sighting in, I first gathered a few key measurements:
- Sight height: 2.5 inches
- Ammunition velocity: 2250 feet per second
- Barrel Length: 10.5"
Then came a couple of important checks to confirm everything was ready:
- Made sure all optic screws were securely tightened.
- Verified that all the ammunition was from the same manufacturer and lot number for consistency.
With these details in place, I plugged the data into the Hornady Ballistic App and set the long-range sight-in distance to 200 yards. I adjusted the app settings from MOA to inch drop and fine-tuned the distance in 2-yard increments. This process suggested an ideal short-range sight-in at 29 yards, so we placed a paper target at 29 yards and used the inside of the chevron as our aiming point. The two shot groups we took there were nice and visible—perfect for moving on to fine-tuning at longer distances.
Short-Range Sight-In Limitations
"While a short-range sight-in can be useful, it has its limitations. For example, at 29 yards, 1 MOA only measures about 0.30 inches in diameter. Since the optic adjusts in 0.25-MOA clicks—around 0.075 inches at 29 yards—and the bullet is more comprehensive than 1 MOA, making precise elevation adjustments at this short range can feel rough. But despite that, a short-range sight-in gives us a reliable alignment between the line of sight and the bullet's trajectory arc, which is a big help for dialing things in at longer ranges.
As you can see in the image, the inside of the chevron serves as the aiming point for calibrating the BDC at both short and long distances.
Going the Distance
We took our next shots at 200 yards, and, as you’ll see in the images, the first two shot groups were a bit low but still hit the steel, which shows that the short-range sight-in got us in the right ballpark. The trajectory and the BDC reticle were in sync by the third shot group. We then moved back to the 300-yard line, testing at both 100 and 300 yards to confirm that the BDC was tracking correctly.
Now, here is the video showing how all this comes together.
thank you Eastwood Outfitters for allowing us to use the range!
