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US Optics ER-25

Posted on February 3, 2013

US Optics website

US Optics ER-25 rifle scope

US Optics ER-25 rifle scope


Since our initial review of the “big” TPAL changes have taken place at US Optics. US Optics has revised their product line, and is no longer offering ERGO models. The standard parallax adjustment is now the TPAL. They condensed the product line to increase efficiency and lower wait times on custom builds. USO has also taken steps to keep scopes with popular options in stock with different dealers.

To accompany the changes, the product line now has different designations. The rifle scopes are now designated by SR, MR, LR and ER (Short Range, Medium Range, Long Range and Extended Range) depending on the magnification and intended use. US Optics still offers reticles, windage knobs and elevation knobs available in minute of angle (MOA), milliards (mrad) and inch per hundred yard (IPHY). This gives the customer the flexibility to have a scope built to his or her preferences.

US Optics ER-25 rifle scope

US Optics ER-25 rifle scope



The SN-3 5-25x is now known as the ER-25. The only objective size available is 58mm. The large objective lens on the ER-25 works like a funnel allowing the scope to transmit as much light as possible through the rifle scope. This ensures a bright, clear image.

US Optics ER-25 rifle scope

Sun shade with ARD


Main tube

The scope no longer has a 30mm or 35mm main tube option. The default tube diameter is 34mm. The larger main tube doesn’t aid in light transmission but does create more room for erector travel. The 34mm main tube allows the rifle scope to have more elevation and windage you can dial. This is excellent for extreme long range shooters and ultra-long range shooters.

EREK elevation

US Optics ER-25 rifle scope

US Optics EREK knob


Select the US Optics erector repositioning knob or EREK and you will be able to utilize the entire range of travel for dialing elevation. EREK elevation knob takes some getting used to while setting it up, but once you have it figured out you will appreciate its virtues. I prefer the low profile of the EREK and generous amount of elevation per revolution. The ER25 has 100 MOA or travel.

Internal ACD

The internal ACD (anti cant device) is another innovative feature from USO. The bubble level is located inside the main tube, and is visible through the sight picture. This option makes leveling the rifle fast and easy.


The digital illumination is available in red, green and blue. The controls have three buttons; the on/off button, increase intensity button and decrease intensity button. When the illumination is turned off it remembers the setting and will remain at that setting when turned back on.

Rapid focus

The ocular of the rifle scope has a rapid eye focus, making it very simple for the shooter to focus the reticle. This is done simply by turning the adjustment in or out until the reticle is sharp and clear.

US Optics ER-25 rifle scope

Magnification ring


US #3 windage knob

The ER-25 comes with the US #3 windage knob. The knob is labeled to indicate which way to dial for left and right windage. The knurled surface is easy to grip and turn. The clicks are solid and positive. Zeroing the knob is done by simply loosening the allen and pulling it away from the scope. You then position it on zero and tighten the allen. The US #3 windage knob is also available with a windage stop. You can also choose to have the windage knob on the left or right side of the scope.

Magnification ring

The magnification ring on the ER-25 is knurled to create a positive gripping surface. The large ring is easy to turn but offers enough resistance that it won’t move by inadvertently bumping it. Going from the lowest magnification (5x) to the highest (25x) requires about 3/4 of a turn. The magnification ring is labeled to indicate which power you’re on.


The scopes reticle is located on the first focal plane, so it scales with the magnification. This feature allows the reticles subtensions to remain consistent. A wide variety of reticles are available to choose from. You can select reticles in MOA, mrad and IPHY. For minute of angle scopes I prefer the CMG MOA and for mrad scopes I like the Mil Scale MPR.

Turret Adjustable Parallax (TPAL)

The parallax control is found on the turret housing. You can select to have it on either the left or right side of the scope. The parallax knob shares the same knurling found on the windage knob and magnification ring.

Length- 18.0”
Weight- 2.5 lbs
Eye relief- 3.5”
Magnification- 5x-25x
Field of view- 16.6 ft @ 100 yards (5x) 5.3 ft @ 100 yards (25x)
Area of travel- 100 MOA
Scope body- 6061-T6 aircraft aluminum

US Optics ER-25 rifle scope

DTA SRS with US Optics ER-25

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