Optic Of The Week. Colt 3x And 4X AR15/M16 Scope


The colt 3×20 and 4x 20 scopes have been around a long time.  Almost as long as the AR15 it was meant for.   It is one of the first optics to ever be designed specifically for the AR15/M16 and was  used during the Vietnam war.

The optic attaches to the carry handle of the upper by using the hole in the center.   A threaded post protrudes out the bottom  and a lever is used to tighten the assembly to the underside securing it tightly into the carry handle slot.

Once the optic is installed, the iron sights on the rifle or carbine can still be used.

The optics have a BDC turret  that can be used after finer zeroing at 100 is done.  To do this you remove the top cover to gain access to the finer adjustment screw.   Windage  adjustment is on the right side of the scope body  and can be adjusted after removing its cover. ll adjustment values are 1/4 inch per click. The rear of the optic is adjustable for parallax.

Once the optic is zeroed at 100 yards, the BDC can be used for  fast and easy range adjustments.

The BDC does match and work pretty well and it is repeatable on  all of the examples I have tried over the years.  The optic is calibrated for the M193  military load which is the 55 grain bullet.  At the time there wasn’t much else out there.  Even later models  can safely assumed to be matched for the M193 type load.

The crosshairs for the scopes came as a  post of a duplex crosshair. I have never been much of a post fan myself.  The glass is very clear on these optics. Of course you can find some that have been used and abused and see  some narfed up glass.    They are not ACOGs, so they can not take that kind of abuse. But that isn’t  to say they are delicate.  They did see actual combat use from Vietnam to the first Gulf War.

Except for a few  very early makes, the Colt optic is usually marked Made In Japan.   The 4x model is the same size as the 3x.

Other than the older models having a slightly shinier finish than the newer made ones, the y are nearly identical.

Like all carryhandle mounted scopes, there is the  usual  issue with cheek weld.  It is something a cheek rest could remedy,  but why bother.   I think the days of this being  your only choice for an optic for your AR/M16  may be over.    Now they are  too collectible and slightly rare to be out using for much more than fun anyways.  And they are a lot of fun to play with. Or even hunt  deer with.   3x and 4x are still usable and hunters and snipers of years and wars past used scopes not even as powerful as 3x for serious work.  They can be used for some pretty decent precise  shooting in  reasonable conditions.

The copes came in a cardboard box with  leather end caps to protect the glass.  Inside was simple instructions on how to zero and use and take care of the optic.


The little scopes are a neat little piece of AR15 history and they are a lot of fun to shoot with. Especially on an older SP1 rifle or M16 clone.   If you have ever wanted to hunt with your old SP1 or clone and  iron sights won’t cut it for you these are just the thing  for getting some real use out of the old retro AR15.


    • no kidding. 10 years ago they were about 125 bucks., now they are 300 or more. Lucky for me I got the 3x for 50 bucks and the new 4x for just 100. the 3x was pawned at a pawn shop my friend owns and when it was lost, he called me up and sold it to me for 50 bucks. the 4x my friend found at a flea market this past weekend and got it for me. Neither one of them had ever been used by any of the previous owners. I got one hell of a lucky break for them

  1. We found a mess of these buried in the armory while I was stationed in the UK. 4x models, new in the box and they did have an NSN to boot. I tried like hell to spin up a DM program so we could get them out on duty and on deployments. I drew up lesson plans, training and range schedules, sustainment training, everything. Even showed how it didn’t conflict with the SOFA or NATO arming agreements. I cited mostly how vastly open air bases are and that these would grant us an advantage of greater stand-off and together ID. Nothing. The military fears change. Fears it immensely.

    Fast forward a few years to a more receptive unit when our M4s came in. We tried briefly to hold onto some of the old A2s to convert to the A4 standard with an ACOG as the DM rifle. It fell by the way side as we had other priorities so the standard became the M4/ACOG combo but actually employing is haphazard unit to unit. Most that I’ve seen don’t.

    • DO you still have all your notes for that DM program you came up with? I sure would like to see that. I’d like to even post that.
      Have you a copy the IBA book “The One Shot Brotherhod” ” by Norm and Rocky Chandler? It was published around 98 or 99 maybe almost 2000 and in it is a pretty long write up some Army Colonel did for updating the DM and he made a case for the M4 with ACOG. how to employ it what the DM’ role would be, tactics etc etc. I read all this before I even knew the Army had an official thing for it going on or was even taking it seriously. I don’t want to blather on about it if you have already read this guy’s write up but he apparently went out got the M4 off the rack, zeroed the ACOG and used M855 to start whacking steel all the way out to 800 and this apparently blew people’s minds at the time. Hejust was prone shooting off a sandbag with all rack grade stuff. I dont think they even thought that was possible haha. The DM is a topic that has always been very interesting to me. I have never been able to learn any real details abut it and what the Army has done with it over the years. About 14 years ago I read some write up where Dave Fortier went to a Army //”class”? where some distinguished rifleman civilian shooters and some Army AMY guys put on some training for a group and they used the sort of famous DMR rifle from that time, the AMU built super heavy fluted barrel with the DD free frloat rail and an ACOG used by that cavalry unit. and Some of them had leupolds, cause Leupold was there giving them out to help the unit,with Larue mounts. BUt I got the idea this was like a one time thing, I then have read other stories of DM clases where the guys used whatever the showed up with and the Army made them use M855, and not the 10K rounds of MK 262 that black hills sent for free. It seems like its a really messy unorganized program to me. Maybe its not even a program? I have no idea how the Army works and honestly reading about it from the outside makes no sense, I would have thought that a DM school was a formal thing like sniper school and everyone would get issued a certain rifle., A “DMR” that was like a M24, all the same. But then later I read its just the guys job, and he uses what he has, Which i think is still good since all M4s are capable or some really great accuracy and with some decent optics and even better, some match ammo, it would do anything some one NOT a sniper would need it to do. ( and even some cases would do sniper work to a certain point). I said all that to say, I really wish I could talk to some one about it that knew what the deal was with the Army and the DM and the Army’s idea of the DMR as a special rifle or as the standard service rifle.

      • Well I was an AF security trooper and not Army so I can’t speak with much authority about what they were/are doing. I don’t have any of that stuff anymore unfortunately. What I relied on, and I’ll freely admit to plagiarism mostly, was a Marine publication in what they called their “X Files” where they published interim, experimental or otherwise transitional doctrine. It had great info on organization, training and even an example qualification course of fire out to 600m. I don’t know if it’s still around or not but it’d be worth a look. I do remember it argued the DM didn’t need a special nor a scoped rifle which I thought was interesting. At the time, around 1999-2000 timeframe, I was trying to learn what everyone else was doing too. When their M16A4 w/ ACOG became standard issue I think it stymied any further official doctrine beyond whatever the local units wanted to do. I wasn’t a Marine of course so that’s my outsider eyes looking in.
        The Army runs, or at least ran, some formal DM training courses at Benning and at Camp Robinson, AR.
        I don’t have the “One Shot Brotherhood” but their write up in DFA Vol 5 really planted the seeds for thought. Our primary argument being the nice, flat by necessity, two mile long airfield we were tasked with securing. Doing something as simple as scoping a rifle was a simple force multiplier. Overwatching movements, point security of entry points, nothing was lost as the troop was still essentially armed with the same issued weapon.

  2. I have a later 3X Colt Scope. I think the elevation adjust may be broken. Reticle looks fine but I do no longer feel a stop in adjusting the scope for 100 yd zero. Is there anyone that nknows wher I can have this checked out and repaired if necessary? I currently use a Colt 4X on the SP1 but have an attachment to the 3X as well. It was on the rifle when I bought it. (that was as soon as I could afford the combo after returning from a great overseas vacation in a warm Asian country).

  3. Were the 3x and 4x scopes manufactured simultaneously or was it a case of early scopes being 3x with later ones being 4x?

    I’d love to hear how privately purchased ones held up in Vietnam.

  4. I have a 3 power carry handle scope, I was informed by Colt in the 80’s that it could be an early m-16 optic made in Japan for US before they began stamping Japan on them, they only stamped (Eyal 3×21 scope, cat no and ser. No.

  5. Just found this page while looking for some information on the Colt 3×20 scope. I’ve had one for many years (20+?) but never used it. My son and I took my Colt Match HBAR out to the range the other day to try it out. We mounted it and first shot a few rounds thru the iron sites to see how the rifle was shooting. I haven’t taken this rifle out in a few years but I am pretty sure that I have the irons sighted for a 50-200 yard zero. It was a little low at 25 yards but straight on. I almost always start such sessions at 25 yards in order to insure that I am on paper. Also we were shooting 55 grain ammo out of a 1 in 7 barrel so we didn’t expect the best accuracy
    We then went to the scope and we were both left (about 6″) and low (about 10″). The vertical adjustment screw was almost impossible to move at first and took some careful muscle and bracing. The windage adjustment was a bit easier. We were able to get it to shoot about 6″ low at 50 yards and straight on. But at 100 yards my son was completely off the target and he is the much better shot.
    We figured that we both were tired and put everything away to follow up on another day.
    I will probably try to get this zeroed at 100 yards and then put it away for special occasions.
    Oh, I also have what I think is a Chinese knock-off which I will need to try out sometime.
    All in all it was a pretty good day for some father-son time

  6. I found an old scope while cleaning out my late brothers apartment. It has Colt marked on it, with made in U.S.A. under it. No serial number, or any other markings. It looks like an AR-15 handle mount scope. Can anyone tell me what it might be worth? It shows some wear from use, but looks good when looking through it. Thanks for any help.

    • Easiest way to find out would be to look around eBay or Gunbroker and see what they’re selling for. Usually you can just search “Colt Scope” and then filter by closed or ended auctions to see the final prices.


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