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Old March 1, 2006, 01:49 PM   #1
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ACOG users, tips? tricks? problems?

Hello, I am wondering if anyone out there has used Trijicons ACOG (Advanced Combat Optical Gunsight) and what your thoughts are on it? I was given one, on a standard (rack grade) M-16A4 and sent to competition.
It has the Illuminated chevron aiming point, and BDC out to 800 meters. The major thing I noticed in the few weeks I shot it there, was that after about 200 meters, accuracy went downhill fast. At 500M, I could barely keep my shots in the scoring rings, which might not mean much to some, but I know I can keep 19 out 20 shots in a 20" circle at that range using Iron sights! The entire team noticed this phenomenon, so that kinda ruled out (in our minds) the possiblity of it just being a crappy shooter, or one bad gun. Possibly a bad lot of ammo. But we havent been able to test the guns afterward with iron sights, or off a rest. After shooting with the ACOG, everyone quickly decided that it was a flawed system. But I'm willing to give it some thought first.
I have decided I dont like the concept of a BDC, It relys too much on set conditions in my mind. I will allow that it should be pretty close, but I dont like to deal in "pretty close".
Anyway, I just want to hear any input from other users, whether you love it or hate it. If you love it; how do you use it? what ranges? what positions?
If you hate it; please tell me why.
Basically, I wont have a choice, when that match comes around again, I will be using that scope again. So I want to know as much as I can about it before then. And not technical stuff, I know all that, I am a Trijicon certified instructor for that particular piece of gear! I want user opinions.
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Old March 1, 2006, 05:40 PM   #2
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What ACOG are you using? I just put a TA31-F on my RRA Free Float 20". I haven't had the chance to shoot it past 100 yards yet but at 100 yrds. Its dead on. I'm shooting 1/2"-1" groups. I don't have any problems with mine yet. What kind of mount you using also?
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Old March 1, 2006, 08:41 PM   #3
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hmm, I dont know what you might know it as, its the newest version Trijicon has come out with, we call it the AN/PVQ-31 Rifle Combat Optic, lol. Mounts? The ones that come with it, the "TA-51" rail mount, goes on the picatinney flattop on the A4.
At 100 yards we didnt have much trouble. Well, ok, the zero likes to float a bit... meaning that you shoot a group, its center, you go up to mark it, and come back and shoot again, to find an equally nice group (i was holding about an inch using the rack A4 and standard issue "green tip" ball ammo) but the group has moved to about an inch high, or a little left, or whatever, all said the movement isnt more than an inch ever, and the rounds for that particular string are all grouped nicely. But the problem comes when trying to use the BDC and the stadia lines as your aimpoint, and extreme loss of accuracy. I understand MOA. And range affects accuracy, but this is beyond what it should be. a 1 inch group @ 100 should be a 3" group @300, maybe a little bigger for wind and such. but not like 12" bigger. Shoot yours at a long range if you get a chance, let me know how it does? It could just be ammo, these new A4's, or even... *gasp* me not used to the scope! I dunno, I pull the trigger the same with it as I do without it... shouldnt be me, I can hold hand sized groups in the prone at 300 all day. But you never know, thats why I'm looking for other users info.
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Old March 2, 2006, 06:18 AM   #4
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Are your mounts shooting loose? We have the ACOGs for our M-4s but mainly we have our shooters qualifying on the M-68 instead. Problem we run across with the M-68 is that the mounts tend to shoot loose after a few rounds and we are having to remind shooters on the line after each string of fire to crank down the mounting knob another click or two.
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Old March 2, 2006, 01:13 PM   #5
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Unfortunately it isnt that easy a fix We have them mounted exactly as Trijicon instructs, and they have not come loose. The Trijicon instructors did a test during our class's zeroing day, where they made one guys scope loose on purpose, and at 100 meters his groups were like 6". They did this so we could all see and recognise the problem if ever our students had that problem.
So if that was my teams problem it would be apparent even at the shorter ranges.
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Old December 15, 2009, 06:07 PM   #6
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so I am shooting on a brand new (literally our of the crate) M-16 A4 with a brand new RCO. I am down at the range and having serious issues at the 500 using this stupid sight. At 200, no issues, good reticle placement, hitting all 5's and one or two 4's. 200 rapid, shot a possible and one string rapid with one dropped outside the 12" ring. 300, no issues, shot a possible's where the trouble starts.

500...shot one, in the berm...moved the reticle so the 4 was on the "shoulders". In the berm. Moved another notch...too high to mark. This goes from in the berm to to high to mark over and over, ranging from putting the 4-5ish center mass. My coach shoots my the berm, too high to mark, in the berm. PMI shoots my the berm, too high, etc. Finally, he hits neckline with the 5 reticle outside and at the bottom of the B'mod target. Why is there so much variation? I am no sniper, but I am usually a crack shot at 500 with iron sights. Not to mention a coach and PMI can't hit using "normal" aiming with the sight.

I fired 6 rounds TOTAL (didn't shoot Monday due to low light conditions I guess at 1700) from 500, but tomorrow is QUAL. Help! It's crappy that I shot the lights out at 200 and 300, but now 500 a PMI, a coach, and myself shot probably 20 rounds (6-8 were mine) and scored MAYBE 4 hits on target, only one being in the black. Needless to say, I'm pretty effing annoyed, not at the coaches, they are great, but the situation.

Do I really need to sight in on the target to my right to hit center mass on my target!?!?!?!?!?!?!?!?!?!
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Old December 15, 2009, 06:30 PM   #7
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I believe the BDC is calibrated for a particular weight bullet if you were shooting a different round other than what its calibrated for I think it would be off the further out you shoot.

From Trijicon's website:

03. What bullet was used to calibrate the ACOG scopes?
The TA01, TA11, & TA31 (.223) were designed for the 5.56mm, 20 inch barrel, 55 grain bullet, and M16/AR15 carry handle mount. The TA01B & TA11C(.308) were designed for the 7.62mm, 20 inch barrel, 168 grain bullet, and M16/AR15 carry handle mount. The TA01NSN was designed specifically for the US Special Operations Command SOPMOD M4 Carbine. To meet their requirements, the reticle bullet drop compensator and range finding stadia lines were based on the trajectory of the 62 grain bullet from a 14.5 inch barrel, flattop mount (Picatinny rail Mil.Std.1913).


» 04. Does bullet weight and/or barrel length effect the reticle bullet drop compensator and range finding stadia lines?
The real issue is not the bullet weight or barrel length, but muzzle velocity, ballistic coefficient, and the distance from height above bore. The difference in trajectory from bullet to bullet or barrel to barrel is usually less then the MOA thickness of the stadia lines.
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Last edited by Palmetto-Pride; December 15, 2009 at 06:39 PM.
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Old December 15, 2009, 06:43 PM   #8
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Zero the optic at the BOTTOM of the chevron at 300 meters. This should be the very top of the verticle black line. If you zero it at 300 YARDS you will be off.

If you are shooting a national match range it is measured in YARDS, not METERS like the ACOG is graduated for. The 400 tick mark (the first tick mark) will cause you to hit high, so aim a little low. The second tick mark, the 500 meter tick mark, will cause you to be only a little high.

One last thing, if you are shooting 62gr M855 ball instead using 55 gr M192 you will have a different ballistic path than the reticle is calibrated for. Although if you zero an ACOG at 300 YARDS with Mk262 and use the tick marks in yards, it is plenty close.

Machine guns are awesome until you have to carry one.
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Old December 16, 2009, 08:27 AM   #9
Lloyd Smale
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did you try shooting that same gun and load with a differnt scope. My first guess would be that your load may be becoming unstable at longer ranges. Also keep in mind that the acog is mostly a close quarters combat sight that is good out to medium range. its not an optic a sniper would use for long range precision shooting. No more the a 6x18 leupold is a good close quarters combat sight.
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Old December 16, 2009, 09:42 AM   #10
Bartholomew Roberts
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1. Are you using the same type of ammunition/rifle that the ACOG is calibrated for? There is an M4 RCO and an M16A4 RCO calibrated for the different velocities. Both are set up to use 62gr M855 ammo.

2. The yards/meters thing that Jimro mentioned. As a quick fix, you can zero the ACOG at 25yds using the 300m aiming point to get you close at 300m.
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Old December 16, 2009, 09:45 AM   #11
Latex Ducky
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Here's something interesting:
There should be a reference to a bible verse on the base of the scope.
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