Articles Comments

Shooting Reviews » Optics, Reviews » Affordable tactical scopes: the Vortex Viper PST vs the Sightron SIII

Affordable tactical scopes: the Vortex Viper PST vs the Sightron SIII

This goal of this review is to look at a couple of budget “tactical” scopes from a practical perspective.  Are they good enough for 1,000 yard shooting, and what trade-offs are involved in buying a budget tactical scope rather than Nightforce, US Optics, Schmidt & Bender, or Hensoldt?  It’s easy to spend more on optics than on the rifle the optics attach to, and my goal here is to offer some guidance for those on a budget.

Reviewer Biases

There are a few points I should get out of the way so you understand where I’m coming from:

  • As someone who’s been involved in serious photography, I have a great deal of respect for high-quality optics.
  • I prefer clarity above magnification.  I’ve scored first-round hits on ten-inch square targets at further than 1,000 yards with a simple (but high quality) ten-power optic, and I could make out 16″ square targets at > 1,500 yards with this same scope.  Higher magnification is nice, but above all I need to be able to distinguish what I’m shooting at.  Clarity rules all.
  • I like scopes that I can sit behind all day without strain.  This means that scopes with greater eye relief are favored over those that require that I keep my eye in the exact right spot.  This makes a greater difference the longer I’ll be behind the gun.
  • Ease of adjustments.  If you’re firing a .308 at 1,000 yards, shooting 175gr Federal Gold Medal Match, then you’re going to require +/- 10 mils of elevation to compensate for bullet drop.  I’d prefer to do this with fewer turns of the elevation knob.  1 turn is way better than 4 from my perspective, even before we start talking about glancing at your knob and knowing what distance is dialed in.

The Optics Being Compared:

I have chosen two scopes that are often described as “good enough” and “bargains,” and am comparing them with a much more expensive higher end optic.  All offer essential features:

  • A one piece tube made of “aircraft grade” aluminum
  • Weatherproofing.  All are sealed against water and nitrogen purged
  • Repeatable adjustments.  This wasn’t tested by me — a quick Google search should give you all the information you need here.
  • Multi-coated optics, and resulting bright images
  • 30mm tubes (35mm on the US Optics scope I’m using as a baseline)
  • Front focal plane reticles, so measurements are correct at all magnifications

All scopes were purchased used, and have some mileage on them.

Sightron SIII 6-24x50mm

Sightron SIII

Sightron SIII

The model being evaluated here is an SIIISS624X50LRMOA, which is available from online discounters for about $915.  This one has the MOA2 reticle and .25 MOA clicks on the adjustment knobs.

Vortex Viper PST 6-24x50mm

Vortex Viper PST

Vortex Viper PST


This is listed as the PST-624F1-A, with the EBR-1 MOA reticle and .25 MOA adjustments.  This offers an illuminated reticle, but otherwise the feature set is comparable to the Sightron.  This is available online for around $950

US Optics SN3

US Optics SN-3

US Optics SN-3

This is a fairly high-end optic that offers a 3-17x zoom range, is nearly indestructible, and costs quite a bit.  Pricing varies as when you order directly from US Optics you can configure everything about the scope, but it’s reasonable to call this a $2,300 – $3,500 scope depending on options.  The one used here was well used by its previous owner, shows quite a bit of wear, and still works great.


Let’s jump right into it.  I took some photos using the following methodology:

  • I set a soda can up 100 yards from the scope on top of the berm behind my pistol range
  • Each scope was turned to maximum magnification (24x on the Sightron and Vortex; 17x on the US Optics)
  • Parallax/focus was adjusted to get the sharpest image
  • Two photos were taken: one at max magnification, and another at 12x magnification.  I’m of the opinion that 12x is a good default and allows plenty of magnification for most shooting.
  • Conditions were overcast and bright.  Positioning the camera was difficult; some photos show glare off the back of the optic that wouldn’t exist when actually shooting.  This is a failure of photographic technique, but the essential points I was trying to show were captured.

12 Power comparison

This is a reasonable default magnification for my shooting, and this power level allows us to compare all the scopes directly.  Here are all three scopes compared side-by-side:

The obvious conclusion is this: at 12 power, all of these scopes offer sufficient clarity and contrast to be usable for precision shooting.

It’s difficult to be consistent enough with a camera to capture the nuances of the different optics.  My subjective perspective is this:

  • The US Optics image seemed brightest and clearest, followed by the Vortex, then the Sightron.  In a direct comparison looking at nothing other than brightness the Vortex is brighter than the US Optics, as one would expect due to the larger objective (50mm vs 44mm) and the presence of an ARD on the US Optics.  Perceptually the USO is brighter though.  This may be due to increased contrast, or it could be the placebo effect in action.
  • All were very clear and usable.  Any of these is likely good enough for long range work, at least in bright conditions like I had when evaluating the optics.
  • All offered etched reticles that were clear and very readable.
  • Parallax compensation on the US Optics and Vortex scopes was labeled, and both were set close to the 100 yard marking after focusing by eye.  The Sightron wasn’t graduated the same way, and had to be focused by eye.

Max Power Comparison

We’re comparing 24 power scopes with 17 power here which really can’t be compared, but let’s try anyway:

Here, looking at the clarity of the “e” in “Coke Zero,” I’d have to give it to the Vortex, followed by the US Optics, then the Sightron.  Overall clarity (again, probably contrast) goes to the US Optics, then the Vortex, then the Sightron.

In my assessment all of these optics are usable even at maximum magnification, and both the Sightron and the Vortex offer higher magnification than the US Optics scope.  This should also be viewed as a pessimistic assessment — parallax/focus was adjusted as best I could by eye, but photographic enlargement will tend to magnify any errors I made.  The images here are much less pleasing than they are to the naked eye when actually using the scope.

Comfort: Eye Relief

The published specifications for eye relief are as follows:

  • Vortex: 4 inches
  • Sightron: 3.8 – 3.8 inches
  • US Optics: 3.5 Inches

In practice, all are comfortable at reasonable magnifications.  At highest power the US Optics is by far the most comfortable, but this may simply be because the exit pupil at 17x on the SN-3 (2.59) is greater than the exit pupil of the other scopes at 24x (2.08).

Build Quality

This is where we’re going to see some differences.  Overall the finish on the Vortex seems higher quality than on the Sightron, but that’s a subjective measurement.  The reason for this is likely largely due to the markings:

Note the ivory-colored markings on the Sightron.

Note the ivory-colored markings on the Sightron.

Coloration on the markings is more as expected on the Vortex

Coloration on the markings is more as expected on the Vortex


The Sightron has crisper adjustments.  The Vortex’s adjustments are distinct, just mushier feeling.  Both are very usable.

The display on the Vortex turrets is more intuitive to me – I know exactly what increment the dial is on.  It’s also clear on the Sightron, but I find it a touch harder to determine in an instant.

The Vortex uses fiber optics on the magnification dial and the elevation knob to make adjustments easier in low light.

The biggest difference here is going to deal with the elevation turrets.  Both scopes offer 1/4 MOA adjustments, but the Sightron has 15 MOA of adjustment per turn of the elevation knob, whereas the Vortex offers only 12.  Digging out my range card for my .308 with a 20″ barrel, a 900 yard shot requires 29.1 MOA adjustment.  29 MOA is a bit less than 2 turns with the Sightron, but 2.5 turns with the Vortex.  Both are usable, but I prefer fewer turns (it’s a bit less than one turn on the US Optics EREK knob, for comparison.)

Zero Stops and the Avoidance of Confusion

It’s frustrating to range a target, start to dial the elevation knob to compensate, realize you forgot to set it to zero at the last firing position, and discover that you have no idea where the dial is currently set.  I watched another student at a long range course struggle with this throughout the course.  A zero stop makes this a non-issue.

If your scope supports zero stops, then you can set the elevation dial to stop turning at a set point.  So if you’re zero’d at 100 yards, you can set the scope to stop turning once the elevation is set for 100 yards (or maybe go a couple of clicks lower to allow for elevation adjustments for closer targets.)  If you need to reset your elevation you just crank it all the way down and know you’ve reached your 100 yard zero, so you can dial in a correction from there.  Simple, intuitive, and hard to screw up.

Now, neither of the budget scopes have a proper zero stop.  Instead, we have simpler solutions:

  • The Vortex has what they call CRS, short for “customizable rotational stop.”  Basically you unscrew the elevation knob, put a spacer in to limit movement below your zero, and turn the knob to point to zero before fastening it back down.  I suppose it works, but the markers at the bottom of the elevation knob that show how many rotations the knob has been turned won’t be reset to zero.  No big deal, but there it is.
  • On the Sightron you’re able to reset the dial so that the ‘0’ is set as you’d expect, but that’s it.  If you’re zero’d where the lower indicator is on 2, then you’ll need to double-check that when dialing in elevation.

This is a convenience issue, and it’s something you can train for.  It’s not a deal breaker, but most of the higher-end tactical scopes will offer a zero stop and it’s well worth having in my opinion.


All the reticles are appropriate for long-range shooting.  They’re sufficiently fine that they don’t disrupt your view of the target, and all offer MOA or MIL markers that can be used for holdovers, wind holds, leading moving targets, and even for rangefinding if you don’t use a laser rangefinder.  All offer FFP reticles so the indicated marks are accurate at all magnification levels.

Which is better?  That depends on which one you like.  I’m not sure I like the central dot on the Sightron, and the hash marks on the Vortex start at 2 MOA rather than something more graduated.  Whatever you buy you’ll need to spend the time to learn the reticle, but if you were issued any of these scopes you could make the reticle work.  On the US Optic scope you can choose from around 20 different designs depending on your preferences, but there’s nothing wrong with any of these reticles.

(This assumes you’re not using the reticle for ranging.  Now that laser rangefinders are cheap and available everywhere I don’t know that it’s worth a lot of effort to range with a reticle for most shooters.  If it is for you, then consider whether 2 MOA as the smallest graduation on the reticle is enough for your needs.)

The Sightron falls behind the others when it comes to illumination, however.

Illuminated Reticles

The Vortex comes with an illuminated reticle, and I have mixed feelings about it.

The Vortex Illumination knob is the one on top here.  Very easy to turn accidentally when putting the rifle up.

The Vortex Illumination knob is the one on top here. Very easy to turn accidentally when storing the rifle.

That’s the illumination knob on top there.  It unscrews to reveal a CR2032 battery that is easy to change out.  I know this because I just changed it, because it accidentally turned itself on and burned the battery out.  The knob is reasonably tight so it takes effort to turn, but I find I’m accidentally turning it on all the time.  Reticle illumination is useless if you can’t keep the battery charged up.

The Vortex illumination is night vision capable:

  • In a good way: the first four illumination positions are invisible to my naked eye.  The first illumination position is perfect when viewed through quality night vision however — perfectly clear and readable through my PVS-7’s.  I assume the additional positions are for less capable (meaning more affordable) units.
  • In a bad way: when any illumination is turned on, it’s visible through the eyepiece and through the objective.  That means that the beautiful night-vision capable illumination level is also visible to night-vision devices downrange.   This won’t matter to most, but it’s a reason I hate red illumination in scopes.  Green makes way more sense to me.


The US Optics SN-3 solves some these problems:

  • The illumination knob is located under a housing, so it’s not accidentally knocked on.  (Current versions are push-button without the housing, but have auto shutoff after one hour, with 100 hours of battery life on the highest setting.)
  • All ten illumination settings are visible to the regular Mark 1 Eyeball.  Choose the illumination level suitable to the current conditions.
  • The problem with light being projected through the objective still exists, so someone downrange can see the illumination if you’re scoping them.  Of course, it’s green on my scope, so either they’ll see a dim green light a long way away with their naked eyes, or they’ll see nothing through night vision devices.  It’s a trade-off, but one that I like.


In general I’m not all that convinced by illuminated reticles.  They make sense in low light (dusk, full moon illumination), but the idea of mounting a PVS-7/PVS-14 and looking through a scope like this seems a bit optimistic.  A clip-on night sight that goes in front of the scope makes more sense.  And costs as much as a used car, but that’s the way of things.


I was pleasantly surprised with the quality of these less expensive tactical scopes.  Simply put: they’re good enough to be competitive in long-range shooting.  You are giving up some flexibility and convenience features vs a scope like the US Optics SN-3, and you’re giving up some objective quality in the optics themselves, but it’s not so much that most people would notice.

And it’s not enough to matter.  If you’re starting out, are on a budget, and aren’t sure what to get, I don’t think you’ll be displeased with either the Sightron SIII or the Vortex Viper. My preference was for the Viper based on the clarity of the optics and the reticle design, but if you look at other reviews online you’ll see it’s a toss-up between the two.  The choice comes down to personal preference or small variations in the sample a particular reviewer has in-hand.

Filed under: Optics, Reviews

Comments are closed.