Compact AR scopes: ACOG, HAMR, SpectreOS

 

Written by ILya Koshkin

 

I have had a reasonable familiarity with the ACOG for quite a while now, but I never really bothered to do an article on one since the bulk of my interest in AR scopes was with the low range variables.  Indeed, in terms of flexibility and capability, good quality variables are the way to go.  However, they are almost invariably heavier than I like and, often, bulkier than I like.  There are some exceptions, of course, with Leupold VX-R 1.25-4×20 coming to mind, but if I choose to go with a variable, I want true 1x on the bottom.

A switch power scope like Elcan Specter DR 1x/4x or IOR 1x/4x Pitbull are interesting options, but they are also a bit heavy weighing well in excess of 20 ounces.

Elcan Specter DR, as much as I like it, is also expensive costing north of $2k.  Now mind you, if I could afford it, I would already own one, but I wanted to look at something with a street price of $1000 to $1200 or thereabouts.

I have some fairly specific notions on the relationship between how much riflescopes these days cost and what I should be getting for that money.

 

When speaking of AR scopes, I loosely divide the price ranges as follows:

– For $500 and under, I am willing to make all sorts of compromises: it just has to hold zero, have a usable reticle and decent image.

– For $1200 and under, the scope has to be exceptionally well executed.  It may not have every functionality or feature I want, but every feature it does have must be executed well

– If it costs north of $2k, I want it to be perfect for what I do.

 

WIth low range variable scopes, I have looked at almost everything out there and I continue to explore new options as they pop-up.  However, there are alternatives that I have not explored as much.

Hence, I started looking at what else is available.  For ultimate speed and compactness, I can always use a small red dot sight a la the highly regarded Aimpoint Micro.  That got me curious and I started looking at a variety of miniature red dot sights.  However, I am a precision guy at heart, so even on lightweight ARs I like to have some amount of magnification available to me.  The next logical step was to consider the ACOG and similar compact fixed power scopes.  An added benefit is that most of them can be paired with a miniature red dot.  However, for this article I looked at the following three sights with no additional accessories:

– Trijicon ACOG 4×32 has been around the longest, so any comparison of such designs must start with it

– Elcan Specter OS is a more recent design, but Elcan has been making scopes of this type for a long time and they go head to head with Trijicon all the time

– Leupold HAMR is comparatively new to the game, but I liked it at SHOT, so I figured it is worth a look.

 

Here is a spec table for the three scopes I looked at (in bold) along with a couple of others:

Trijicon ACOG 4×32

Elcan Specter OS 4×32

Leupold HAMR 4×24

Hensoldt ZO 4x30i

Browe 4×32

Length, in

5.8

6

5.7

5.47

6.3

Weight, oz

Listed:

9.9 (w/o mount)

or 14 with mount

Weighed:

14.65 with mount

Listed: 18.6

with mount

Weighed: 18.55 with mount

Listed: 14.8

with mount

Weighed: 13.5 with mount

21.16

17

Eye Relief, in

1.5

2.75

2.8

2.56

1.5

FOV, ft@1000yards

36.8 (7 deg)

31.5 (6 deg)

31.5 (6 deg)

42 (8 deg)

36.8 (7 deg)

Click Value

0.5 MOA

0.5 MOA

1 MOA

0.2 mrad

0.5 MOA

Illumination

Fiber-optic and tritium

Dual mode battery power

Single mode battery power

Battery powered

Battery with autocompensation

Price

$1218

$1254

$1299

$1590

$1184

I should have probably looked at the Hensoldt ZO 4×30 as well, but I did not have one easily available to me, so I might do so at a later date.  It is a bit more expensive than I would like for this category and a bit on the heavy side, but the one I saw at SHOT was a nice piece.  I suspect I will not be able to resist the temptation and test it at some point.  I like the very wide FOV on that sight.  The first version had a freakishly short eye relief, but Hensoldt changed the design and the eyerelief is very usable now.

Browe scopes are very similar to the Trijicon, except they have a rather innovative reticle illumination technology which taps a little bit of the light entering the scopes and autoscales based on that reading.  I figured that if I like the ACOG 4×32, I can alway revisit Browe later.

All three of the scopes I looked at are 4x in magnification.  The reason I picked 4x is that the HAMR is only available as a 4×24.  Both Trijicon and Elcan offer other magnifications.  In a way, that stacks the deck a little against Elcan, since its Atos OS 3x sights are lighter and I am looking for a light scope.  SImilarly, it is not strictly speaking fair to Trijicon because I have seen enough ACOGs to know that the 4×32 has the tightest eye relief.  Under different circumstances, I would probably pick a 3×30 Trijicon, but the 4×32 is lighter.

With all that said, I decided that there are too many options here to cover in one article, so I took the three 4x scopes and stuck with them.

Before, I get too much further, I will say that one of my takeaways is that I should also consider lower magnification scopes of this type for a future article.  There are some interesting designs out there that I want to look at.  In the future, perhaps I will pit the 3×30 ACOG against Elcan’s 3x ATOS sight.

 

Here is a brief summary of what I found with these three scopes:

– Optically, Elcan walks all over the competition, and it is easily the best one of the three for precision shooting, while being very capable for everything else.  I really like the illumination scheme on the Elcan.

– HAMR offers additional mounting flexibility, which came very useful for me, and is the lightest of the three once you actually weigh the scopes.

– I do not particularly care for the reticle in any of these scopes, but Elcan gave me the most precision, while HAMR was the fastest.  With the ACOG, I should have gotten the circle dot reticle which is similar to the HAMR.  The holdovers are not especially useful with any of them once you get past 400 yards.

– If you are getting older and your eyes are not what they used to be, the HAMR is the only one of the three with adjustable eyepiece focus.

– The short eyerelief of the ACOG made it much harder to get behind quickly and comfortably than the other two.

 

I am searching for a scope for a particular rifle and for this application the Leupold HAMR was the best fit of the three scopes I tested, while the ACOG did not work well on it at all.  Elcan was somewhere in between.  If I were to switch to a collapsible stock on that AR, Elcan will become the perfect fit.

 

Now onto the details….

 

The rifle I want a scope like this for is very light.  It has a pencil thin melonited barrel from Voodoo Innovations, carbon fiber handguard and ACE ultra light stock.  It is my SHTF rifle, so I insist on having back-up iron sights (BUIS) on it.  I picked the smallest available (that I could find) rear folding sight from Knights Armament, but I still have to mount the scope a little further forward than I could have without the BUIS.  Couple that with a fixed length stock and what you get is issues with eye relief.

 

CAS-1_zps17bd3490.jpg

 

I did bring another lower assembly with me that is nearly identical, except for having a collapsible Vltor Imod stock.  That rendered ACOG almost usable and made Elcan a perfect fit.  A lot of the tests I did with a collapsible stock lower to be fair to all three scopes.

 

Both the ACOG and the HAMR come with a flat top adaptor, but the ACOG adaptor can only be mounted one way, while the HAMR has a couple of position options that came really useful.

 

Here is a picture that shows the approximate location of the oculars of the three scopes:

 

CAS-8_zpsd109d15c.jpg

 

Since the ACOG’s eyerelief is a more than an inch shorter than that of Elcan and Leupold, it was difficult to use with a fixed length stock and BUIS in place.

 

The SpecterOS comes with a QD mount (ARMS levers) and external windage and elevation adjustments.  I am not a huge fan of ARMS levers, but best I can tell this latest iteration is pretty sturdy and I had no issues with them.  Perhaps more importantly, this Elcan returned to zero sufficiently for me to not see a perceptible difference in POI.

 

Both the HAMR and the ACOG have the regular thumbscrews with two crossbolts on their mounts.  The crossbolts on the ACOG adaptor are round, while the HAMR crossbolts have flattened sections.  The HAMR also came back to zero well, if I was somewhat paying attention to even and consistent screw tightening.  The ACOG shifted zero a fair bit more, but there are a many better aftermarket options for an ACOG mount, if you need a quality QD mount.

 

In terms of mechanical qualities, all three scopes look like they can take a beating.  I suppose the fiber optic collector of the ACOG is a weak spot, but there are LED powered version of the ACOG, so you do not have to get the fiberoptic one if you do not like it.  I did not have any durability issues with any of these and they held zero without any concerns on my part.

 

The ACOG and the HAMR have internal windage and elevation adjustments, while the SpectreOS adjustments are external.  I confess to not checking tracking on these beyond the sight in process.  These scopes are not designed to be adjusted all the time.  While I was sighting them in, the POI movement agreed with the amounts I was dialing.

 

If push comes to shove, the Elcan’s elevation adjustment allows for dialing in shots and I played with it a little.  It worked surprisingly well.  The large knurled adjustment ring under the scope body needs to be unlocked using a coin or a knife blade or a screw driver (or a sturdy thumbnail), after which it can be easily rotated.  Of these three scopes, the Elcan is easily the best for precision shooting so experimented with it in that capacity with surprisingly good results.  There is a lot to be said, I suppose, about nicely optimized designs even with moderate magnifications.  I could easily use this sight to the extend of the range of the 5.56×45 round and would not have any issues using it on a precise semi-auto 7.62×51 either.

 

Ultimately, all three of these scopes are designed to be used primarily with holdover reticles.  From left to right: Elcan, Trijicon, Leupold

 

CAS-9_zps17577630.jpgCAS-10_zpsd10a2138.jpgCAS-11_zps55b5e26a.jpg

 

To my considerable surprise, the ACOG’s chevron reticle did not agree well with me at all.  I’ve used chevrons in a variety of scopes over the years and liked them.  However, that was usually in different designs.  In the ACOG, I suspect that the Horseshoe Dot reticle would work much better for me.  Please note that in terms of visibility, all three reticles were quite visible (much more so than in these small pictures).

 

The Leupold reticle is designed with NATO standard M855 ammo in mind.  Ditto for the Elcan, although neither mentions barrel length.  The ACOG reticle (except for the TA01NSN model) is calibrated with a 55gr 5.56 ammo out of a 20” barrel.

 

The only problem is that I use 77gr and 75gr ammo (similar to Mk 262) virtually exclusively.

 

Here is how the external ballistics compare (typically) in terms of drop and wind, both in milliradians (courtesy of JBM Ballistics website):

 

62gr M855

55gr M193

77gr MK262

Range

Drop

Drop

Drop

(yd)

(mil)

(mil)

(mil)

100

0.5

0.4

0.5

200

0

0

0

300

-0.8

-0.7

-0.8

400

-1.9

-1.7

-1.9

500

-3.2

-3

-3.1

600

-4.9

-4.7

-4.5

700

-6.9

-6.7

-6.3

800

-9.4

-9.2

-8.3

900

-12.3

-12.3

-10.8

1000

-15.6

-15.8

-13.8

62gr M855

55gr M193

77gr MK262

Range

Windage

Windage

Windage

(yd)

(mil)

(mil)

(mil)

100

0.3

0.3

0.3

200

0.7

0.7

0.6

300

1.1

1.1

0.9

400

1.6

1.6

1.2

500

2.1

2.2

1.6

600

2.7

2.8

2

700

3.3

3.5

2.5

800

3.9

4.2

3.1

900

4.5

4.9

3.7

1000

5.1

5.5

4.2

 

The drop is pretty close, especially if you stay within 400 yards, but the windage is not.

 

I like to have some sort of a horizontal stadia to give me a rough idea of how level I am with respect to the surrounding.  Except I like the hashes on the horizontal line to be spaced according to something with known periodicity, like milliradians.  From that point on, I can easily figure out what wind holds that corresponds to for any cartridge.  Unfortunately, Leupold insisted in putting in windage hold marks that corresponds to 5mph, 10mph and so on wind exactly perpendicular to your line of sight.  That can be made useful after a lot of practice and wasted ammo (which is a polite way of expressing what I think of this reticle feature while sticking to words fit for printing).

 

Optically, the comparison turned out to be far simpler than I had expected: the SpectreOS walked all over the other two scopes with HAMR edging out the ACOG for second place.  In all fairness, all three scopes performed better than I expected, but the ACOG is the oldest design here and it shows.

I stretched the legs of the rifle the scopes were sitting on and as far as precision shooting goes, the Elcan has a clear advantage over the other two scopes here.  I could resolve better with it, contrast was better and the scope was easier to get behind.

In terms of actual usability, the difference was also considerable with the Elcan and Leuold being very easy to get behind and the Trijicon turning out to be a bit tricky.  I suppose it is the combination of short eye relief and small ocular lens.

The illumination scheme was also different between these three sights, but before I get into that, it is worth mentioning that Tijicon offer the ACOG with a variety of different illumination schemes: tritium only, tritium with fiber optics, LED only, etc.  The version I looked at is tritium with fiber optics and I specifically chose this one to see how I like it.  I know full well that I like the ACOG with a battery powered LED, but the fiber optics was interesting to look at.

As it were, I found all three illumination schemes to be quite serviceable.  The Leupold and Elcan have battery powered illumination with the Leupold offering a conventional turret on the right side of the scope body,  It has sufficient dynamic range for both low light and bright light shooting and proved to be pretty fast in use.  The illumination is easily day visible even on bright California days.

The Elcan illumination is also controlled by a rotary turret except it sits on the left side of the scope body, which works quite well on ARs.  When I needed to make a quick adjustment on the HAMR I had to reach over the scope with my left hand, since ARs are designed to be run with the left hand.   When I tried shooting with a support sling, it was easier to run the HAMR, since I was doing it with the right hand.  The left arm was locked in place by the sling.

I wonder why the reticle brightness adjustment is not on top of the scope body.  A low and wide turret there would be convenient for operation with either hand.  It might interfere with top-mounted mini red dot sights though.

The SpectreOS illumination differs from the HAMR in another significant way: it has two modes depending on which direction you rotate the turret two away from the OFF position.  The bright light mode illuminated the tiny center crosshair and is visible during the day.  The low light mode illuminated the whole reticle pattern, but faintly enough to keep you eyes night adjusted.  Both modes have several brightness levels.  I found the setup to be well conceived and well executed.  In low light mode, I could executed precision shots in very dim lighting and the generally excellent optical quality of the Elcan definitely helped as well.

The ACOG illumination has some strengths and some weaknesses.  The biggest strength is also the biggest weakness: it is always on.  It is bright and easy to use.  It is fast to pick up as well.  However, if the lighting conditions where you are differ significantly from where you are aiming, it does not always work all that well.  Aiming at a bright spot from inside a dark room was not optimal, while aiming from a brightly lit area into shadows had other set of problems with a very overpowering reticle.  Still, those are fairkly extreme conditions and if you do not like this illumination scheme, Trijicon offers a variety of illumination options.

Lastly, here are some conclusions and closing thoughts:

  • Between these three scopes, I thought that ACOG was the hardest to use.  The HAMR and the SpectreOS have a clear edge there.

  • For a lightweight carbine, the HAMR is probably the best option owing to its light weight and overall good performance.

  • If you can live with four extra ounces, the Elcan SpectreOS is a more refined and versatile scope with the best optics of the bunch.

  • If you need ocular adjustment in your scope, the Leupold is the only game in town.

Having played with these 4x scopes, I found that while I can use them with good speed, adding a miniature red dot is a good idea.  All three have provisions for mounting a red dot and I will likely do so in the near future.

 Posted by at 11:22 am

  2 Responses to “Compact AR scopes: ACOG, HAMR, SpectreOS”

  1. […] only reviews I could find were from The Firearm Blog, and Ilya’s excellent comparison over at Optics Thoughts (the latter of which was the one that pushed me over the edge to purchase it). I imagine that most […]

  2. […] I suspect the SpecterOS is not more popular because it is in the same category as Trijicon’s ubiquitous ACOG series. ACOGs have a reputation ruggedness, excellent optical quality, and battery-free illumination through the use of fiber optics and tritium. For most US shooters shopping for a military quality optic in the +/- $1,000 range, there wasn’t much of a reason to look elsewhere. I was hesitant myself, since it’s an unknown, and the only solid review I could find was Ilya’s excellent work at Optics Thoughts. […]