View Full Version : Which ACOG to get?
So my next AR is gonna be a 12.5 inch barreled gun with a carbine length gas system. I’m pretty set on running an ACOG on it. If you go on Trijicon’s website there are tons of 4x options that claim to have the BDC for 5.56. I know that the model the military has used extensively on the M4 is specifically calibrated for the BDC out of a 14.5 inch barrel. Now looking at the ballistics out of a 12.5 inch barrel vs 14.5 inch barrel, there is some loss in velocity but it is not a HUGE loss. I have seen a decent amount of people running ACOGs on 12.5 setups but my question is which 4x option will matchup CLOSEST to 12.5 ballistics? I saw on a livestream Lucas from TREX arms was running an ACOG on a 12.5 and he said he was hitting steel at 400 easy with it, which is all I would expect the 12.5 to do. I’m assuming the model that will match up CLOSEST to the ballistics of the 12.5 is whichever model is calibrated for the bullet drop of a 5.56 out of a 14.5 barrel but I want to know which one specifically? And do they make that model with a green chevron or with any green options? I also was planning on running this gun suppressed full time so I’m assuming I will get some velocity back but not a whole lot. And the majority of the stuff I will be shooting and what my guns are zeroed with is 55 grain XM193. Thanks guys.
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NSN version for 62gr should be pretty close, if you true it a little further out.
NSN version for 62gr should be pretty close, if you true it a little further out.
Also, the majority of the stuff I will be shooting is 55 grain XM193.
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I just set up my 14.5 with a TA01NSN, and I'm running 69 gr RMR bullets hand loaded to about 2850 fps.
I was sure the load wouldn't keep up with the reticle, but the ammo is actually outpacing the reticle. I'm holding belt buckle on a 500 yard target to get close to center mass.
My COG and load would likely match up good with a 12.5. I bet XM193 tracks pretty good.
bamashooter
03-01-22, 08:15
As you know, ACOG and all others are spec'd to a single round and whether people want to admit it or not, a specific barrel length. Just they way it is and can only be. With that said, extended distances aside and a willingness to accept a less than designed for result, you should be able to satisfy your desire for an optic with BDC; within reason. You should be able to get a disabling hit at under 400m / multiple quick hits <300m once you establish your primary zero.
As you know, ACOG and all others are spec'd to a single round and whether people want to admit it or not, a specific barrel length. Just they way it is and can only be. With that said, extended distances aside and a willingness to accept a less than designed for result, you should be able to satisfy your desire for an optic with BDC; within reason. You should be able to get a disabling hit at under 400m / multiple quick hits <300m once you establish your primary zero.
I’ve seen videos of people hitting steel out to even 500 yards with them on a 12.5. If it was still a combat effective reticle on a 12.5 out to 400 yards I would call that a success. But again I am not sure which 4x ACOG to go with. Whichever model is for the 14.5 I would assume would work best but I don’t know.
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Also, the majority of the stuff I will be shooting is 55 grain XM193.
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If your main objective is just getting to 400, I think you’ll be fine with a version meant for 14.5” M855. XM193 from a 12.5” barrel isn’t too far off in velocity from M855 from a 14.5” gun, so it should work. Like MarkM, I shoot 68gr ammo to 500 or 600 using BDC reticles similar to the ACOG’s all the time. None of those reticles were designed for that ammo weight, and most weren’t even designed around my 14.5” or 12.5” barrels, but I do just fine.
Are you using Winchester, or Federal XM193? What target types?
If your main objective is just getting to 400, I think you’ll be fine with a version meant for 14.5” M855. XM193 from a 12.5” barrel isn’t too far off in velocity from M855 from a 14.5” gun, so it should work. Like MarkM, I shoot 68gr ammo to 500 or 600 using BDC reticles similar to the ACOG’s all the time. None of those reticles were designed for that ammo weight, and most weren’t even designed around my 14.5” or 12.5” barrels, but I do just fine.
Are you using Winchester, or Federal XM193? What target types?
The mix of my ammo stash right now is Hornady Frontier XM193, Federal American Eagle XM193, and I do have some of PMC’s XM855 load too. The majority of what I shoot and what I will buy in the future is XM193. Keep in mind I am also going to be running this gun suppressed a lot of the time too. So that will bring SOME (not a a lot but some) velocity back as well, narrowing the gap between 12.5 and 14.5 ballistics a little bit more.
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The mix of my ammo stash right now is Hornady Frontier XM193, Federal American Eagle XM193, and I do have some of PMC’s XM855 load too. The majority of what I shoot and what I will buy in the future is XM193. Keep in mind I am also going to be running this gun suppressed a lot of the time too. So that will bring SOME (not a a lot but some) velocity back as well, narrowing the gap between 12.5 and 14.5 ballistics a little bit more.
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On E-types, you could probably mix all of those up in a mag and hit at 400 with a 12.5” and ACOG. With B/C steel or F-Types you’ll likely be fine with whichever you zero it for. They’ll all be moving close to the 2950-3150fps the reticle is designed for.
I think you’ll be fine with a TA31RCO or a TA01NSN, in that order.
Edit: *the difference between a 14.5” and a suppressed 12.5” velocity is rather slim*
The key to using different ammo and barrel lengths than what a reticle is designed for is to true it up further out. If your zero is perfect at 100, it might be significantly off at 500 with the hold marks, if the velocity is too far off. But if you true it up at 400-500, it’ll be good enough from 0-500.
As an example, I’ve been shooting an 8x LPVO with a reticle designed for 20” barrels, but I’m using on a 14.5” thats old enough that the velocities are slightly under that of my 12.5”. I zeroed it at 300, then shot 500 and made a couple small adjustments. Both with 68gr Frontier 5.56. I then shot third in a match that went out to 500. And now I’ve discovered I can put 55gr steel case in it and hit to at least 400 with ease, without touching my zero.
Sidenote, I’d stop buying that Frontier ammo. I’ve gone through 3 cases of the 68gr 5.56, chronoing 5-10% of the case. Each case has had one round thats around 200fps faster than all of its friends in the same 12.5” or 14.5” barrels. That means that there is probably around 10 overpressure events per case in the 90+% that don’t get seen on a chrono.
I think the 193 clone Frontier is the one associated with kabooms on TOS.
He should also check his POI with all the ammo types at 100 yards. Barrels are sometimes weird where they'll shoot way off with different projectiles.
On E-types, you could probably mix all of those up in a mag and hit at 400 with a 12.5” and ACOG. With B/C steel or F-Types you’ll likely be fine with whichever you zero it for. They’ll all be moving close to the 2950-3150fps the reticle is designed for.
I think you’ll be fine with a TA31RCO or a TA01NSN, in that order.
Edit: *the difference between a 14.5” and a suppressed 12.5” velocity is rather slim*
The key to using different ammo and barrel lengths than what a reticle is designed for is to true it up further out. If your zero is perfect at 100, it might be significantly off at 500 with the hold marks, if the velocity is too far off. But if you true it up at 400-500, it’ll be good enough from 0-500.
As an example, I’ve been shooting an 8x LPVO with a reticle designed for 20” barrels, but I’m using on a 14.5” thats old enough that the velocities are slightly under that of my 12.5”. I zeroed it at 300, then shot 500 and made a couple small adjustments. Both with 68gr Frontier 5.56. I then shot third in a match that went out to 500. And now I’ve discovered I can put 55gr steel case in it and hit to at least 400 with ease, without touching my zero.
Sidenote, I’d stop buying that Frontier ammo. I’ve gone through 3 cases of the 68gr 5.56, chronoing 5-10% of the case. Each case has had one round thats around 200fps faster than all of its friends in the same 12.5” or 14.5” barrels. That means that there is probably around 10 overpressure events per case in the 90+% that don’t get seen on a chrono.
I think the 193 clone Frontier is the one associated with kabooms on TOS.
The TA31RCO looks like a very good option. I looked it up and Trijicon advertises it as BDC for the M4 (14.5 inch barrel). This should match up pretty close to what I plan on building. Now I was planning on running a Silencerco 5.56 Saker K on the end of my 12.5 build. Even with it being a K can and not a full length 5.56 can, do you still think the velocity will be close enough to an unsuppressed 14.5? I know I’m splitting hairs here but this is good information you just gave me thank you.
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He should also check his POI with all the ammo types at 100 yards. Barrels are sometimes weird where they'll shoot way off with different projectiles.
Absolutely. There’s some weird barrel voodoo that can whack your bullets a couple minutes off, whereas some don’t seem to care at all. I think as long as he zeros it with whatever case he’s shooting at the time, the ACOG will do its job, though.
Absolutely. There’s some weird barrel voodoo that can whack your bullets a couple minutes off, whereas some don’t seem to care at all. I think as long as he zeros it with whatever case he’s shooting at the time, the ACOG will do its job, though.
That’s what I plan on doing.
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The TA31RCO looks like a very good option. I looked it up and Trijicon advertises it as BDC for the M4 (14.5 inch barrel). This should match up pretty close to what I plan on building. Now I was planning on running a Silencerco 5.56 Saker K on the end of my 12.5 build. Even with it being a K can and not a full length 5.56 can, do you still think the velocity will be close enough to an unsuppressed 14.5? I know I’m splitting hairs here but this is good information you just gave me thank you.
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If you buy 10 12.5” barrels and put cans on them, and 10 14.5” unsuppressed barrels, you may see overlap in velocities, especially if the 14.5” guns have a bunch of rounds through them (.mil). In any case, the difference will almost certainly be unnoticeable.
And, you’re welcome.
If you buy 10 12.5” barrels and put cans on them, and 10 14.5” unsuppressed barrels, you may see overlap in velocities, especially if the 14.5” guns have a bunch of rounds through them (.mil). In any case, the difference will almost certainly be unnoticeable.
And, you’re welcome.
Even with running a shorter can like a Saker K from SilencerCo?
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Even with running a shorter can like a Saker K from SilencerCo?
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Yeah, absolutely. The velocity difference, unscientifically between a 12.5” and a 14.5” is roughly 100fps, making a 12.5” pretty much halfway between an 11.5” and a 14.5”. But I’ve observed freebore boost as high as 75fps with K silencers. Its typically a little less, 25-40fps, sometimes none.
So, we can say that in many cases a 12.5” is somewhere within 100fps or less of a 14.5”, which isn’t really that much more than the extreme spread with ball ammo. Peep my chrono thread here: https://www.m4carbine.net/showthread.php?220992-Labradar-5-56-data-1168 and this dudes chrono thread over there: https://www.ar15.com/forums/ar-15/-/16-714088/? Note that with one brand of ball ammo, he showed only 10fps difference between his 12.5” and 14.5”.
The variability from one barrel to the next can easily be 100fps, so its really not that much difference to the reticle. Add in varying temperatures throughout the year, and you’ll see that the ACOG’s reticle has to accommodate a spread in 14.5” velocities that would overlap with a 12.5” or a 20”. Also, with the reticle made for 62gr from a 14.5”, and you shooting 55gr from a 12.5”, it’ll probably line up pretty close within about 500~ish yards. After that, BC and errors in range estimation start to matter more than 100fps.
I’ve got a 14.5” thats getting old and slowing down, about 50-75fps slow, and there is overlap with my newest 12.5” using 62gr and 68gr ammo. Sometimes the 12.5” is actually faster, and that was also true of my last new 12.3” barrel and its 1 year older 16” friend that was slow.
I forgot to mention… there’s another choice to make with ACOGs: do you want short eye relief with a great field of view and 4x, or do you want longer eye relief with less field of view and 3.5x?
I always thought that free bore boost was a bunch of liberal propaganda. I've never measured it. People used to also say that suppressors slowed the bullet down too.
Which (if any) ACOGs were designed to be compatible with a rifle-length weapon?
Which (if any) ACOGs were designed to be compatible with a rifle-length weapon?
I think the TA31RCO was issued in the corpse with A4s. Someone will have to check my memory.
Yeah, absolutely. The velocity difference, unscientifically between a 12.5” and a 14.5” is roughly 100fps, making a 12.5” pretty much halfway between an 11.5” and a 14.5”. But I’ve observed freebore boost as high as 75fps with K silencers. Its typically a little less, 25-40fps, sometimes none.
So, we can say that in many cases a 12.5” is somewhere within 100fps or less of a 14.5”, which isn’t really that much more than the extreme spread with ball ammo. Peep my chrono thread here: https://www.m4carbine.net/showthread.php?220992-Labradar-5-56-data-1168 and this dudes chrono thread over there: https://www.ar15.com/forums/ar-15/-/16-714088/? Note that with one brand of ball ammo, he showed only 10fps difference between his 12.5” and 14.5”.
The variability from one barrel to the next can easily be 100fps, so its really not that much difference to the reticle. Add in varying temperatures throughout the year, and you’ll see that the ACOG’s reticle has to accommodate a spread in 14.5” velocities that would overlap with a 12.5” or a 20”. Also, with the reticle made for 62gr from a 14.5”, and you shooting 55gr from a 12.5”, it’ll probably line up pretty close within about 500~ish yards. After that, BC and errors in range estimation start to matter more than 100fps.
I’ve got a 14.5” thats getting old and slowing down, about 50-75fps slow, and there is overlap with my newest 12.5” using 62gr and 68gr ammo. Sometimes the 12.5” is actually faster, and that was also true of my last new 12.3” barrel and its 1 year older 16” friend that was slow.
I forgot to mention… there’s another choice to make with ACOGs: do you want short eye relief with a great field of view and 4x, or do you want longer eye relief with less field of view and 3.5x?
In the second thread you linked me to, he was shooting a 12.5 suppressed and the 14.5 was suppressed as well. So theoretically as close as those numbers are on that chart between the two barrel lengths both suppressed, they should be even CLOSER for a suppressed 12.5 compared to an UNsuppressed 14.5 since the suppressed 14.5 is probably getting some additional velocity boost off of that can, correct?
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In the second thread you linked me to, he was shooting a 12.5 suppressed and the 14.5 was suppressed as well. So theoretically as close as those numbers are on that chart between the two barrel lengths both suppressed, they should be even CLOSER for a suppressed 12.5 compared to an UNsuppressed 14.5 since the suppressed 14.5 is probably getting some additional velocity boost off of that can, correct?
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Pretty much. But don’t bank on more than 25fps freebore boost. If you get more; great, if you get less, inconsequential.
I think you’ll be able to achieve your objective.
Which (if any) ACOGs were designed to be compatible with a rifle-length weapon?
RCO-A4 is designed for 20" barrels.
RCO-A4 is designed for 20" barrels.
Thats the TA31 RCO A4/M4, isn’t it? I have a hard time navigating Triji’s nomenclature sometimes.
I have a hard time navigating Triji’s nomenclature sometimes.
I never could figure out how guys on the forums would talk back and forth knowing which models were what.
Thats the TA31 RCO A4/M4, isn’t it? I have a hard time navigating Triji’s nomenclature sometimes.
I believe so. It's what I've used for Marksmanship events for the last few years, and I'm a fan despite the short eye relief. One day I hope to grab a RCO-M4 for a head to head comparison to my P4xi.
Ive had a TA01NSN for years. Its great for accuracy and I figured out the zero for mk262 on a 16" barrel using the BDC. The crosshairs out do the chevron all day IMO.
The one item I would definitely buy no matter what acog is the Macedon Defense KRAM Spacer. Its one of the greatest things designed for anything running a TA51 pattern mount.
Ive had a TA01NSN for years. Its great for accuracy and I figured out the zero for mk262 on a 16" barrel using the BDC. The crosshairs out do the chevron all day IMO.
The one item I would definitely buy no matter what acog is the Macedon Defense KRAM Spacer. Its one of the greatest things designed for anything running a TA51 pattern mount.
Where can you find those?
Where can you find those?
Weapon outfitters used to stock the KRAM.
https://www.weaponoutfitters.com/macedon-defense-kram-optics-spacer.html
I am about to pull the trigger on a ACOG TA11, the 3.5X model. I have a red dot w/magnifier that I like so I'm selling one RD with another mag to go in a different direction.
The one item I would definitely buy no matter what acog is the Macedon Defense KRAM Spacer. Its one of the greatest things designed for anything running a TA51 pattern mount.
Is that the thing that Will and Mark developed? I was asking Pappabear about this the other day, and I couldn't figure out what the benefit was. I remember Gunz really liked it, but I just got my TA01NSN, and don't have a ton of COG experience.
Is that the thing that Will and Mark developed? I was asking Pappabear about this the other day, and I couldn't figure out what the benefit was. I remember Gunz really liked it, but I just got my TA01NSN, and don't have a ton of COG experience.
It helps extend the ACOG further to the rear to help extend your length of pull when using a TA31. On a rifle with an A2 stock, it's a God send. With an adjustable stock, it gives you the ability to run a longer LOP and still have appropriate eye relief.
I used to just pull the BUIS off of my M4 and mount the ACOG as far back as I could. The KRAM will achieve this while allowing you to run a QD mount with BUIS, or extend the ACOG even further back for shooters who need the longer LOP.
Is that the thing that Will and Mark developed? I was asking Pappabear about this the other day, and I couldn't figure out what the benefit was. I remember Gunz really liked it, but I just got my TA01NSN, and don't have a ton of COG experience.
Yeah, it does all of what GTF said plus raises it up to a "lower 1/3rd" height which makes catching the eye box much faster.
Got it. Now that you mention the rifle stock... Yep! I could see that being a big help.
Yeah, it does all of what GTF said plus raises it up to a "lower 1/3rd" height which makes catching the eye box much faster.
I actually forgot it did that, thanks for the reminder.
To answer the original question:
https://i.imgur.com/ZXsbICo.jpg
Press Check
03-03-22, 17:24
Over the span of 15 years, I have owned most of the 4x32 ACOG's, including the LED model, and what a mistake that was. Long story short, always ended up back where I started, which was the TA01 with the crosshair reticle.
Over the span of 15 years, I have owned most of the 4x32 ACOG's, including the LED model, and what a mistake that was. Long story short, always ended up back where I started, which was the TA01 with the crosshair reticle.
That's the only one I ever wanted. The chevron isn't TOO bad. But it's almost like you need to get a shot long enough to clear the busy clutter before you get to the BDC marks that are less distracting.
As far as zeroing the COGs, you can always zero at you most desired distance, ie, 500Yards then go back and learn your come ups from there. Like maybe you will be dead on at 400 or 500 but and inch off at 100 and you just know that DOPE. For some reason we went to re-zero my COGs last week and one 4X was 6 inches high. We were like how the fck is my COG hitting a solid 6 inches high. Maybe an inch or two but WTF, 6 inches. Always good to check you r zero.
PB
As you know, ACOG and all others are spec'd to a single round and whether people want to admit it or not, a specific barrel length. Just they way it is and can only be. With that said, extended distances aside and a willingness to accept a less than designed for result, you should be able to satisfy your desire for an optic with BDC; within reason. You should be able to get a disabling hit at under 400m / multiple quick hits <300m once you establish your primary zero.
I’ve used a 4X ACOG on a 7.62x39 AR with good results out to 400 yards with some success at 500 yards, prone off of a bipod. At 300 yards an 8” gong was easy just use the 400 yard line and hold a little high. The problem with bcd is that they will probably not be exact for anything. But if you shoot you can figure out the holds.
I’ve used a 4X ACOG on a 7.62x39 AR with good results out to 400 yards with some success at 500 yards, prone off of a bipod. At 300 yards an 8” gong was easy just use the 400 yard line and hold a little high. The problem with bcd is that they will probably not be exact for anything. But if you shoot you can figure out the holds.
Yep. I don't mind the Reticle not tracking exactly. It's square range stuff anyway. If you get to unknown distances (UKD), precise tracking isn't critical if you're range estimating in the first place.
(now if you're laser ranging and running a COG, you're a wildman!)
Hammer_Man
03-25-22, 08:48
Have any of you used a 3.5x ACOG (TA11) with a 14.5” barrel? I’m building another M4, and I prefer the eye relief of the TA11 over the TA31.
Have any of you used a 3.5x ACOG (TA11) with a 14.5” barrel? I’m building another M4, and I prefer the eye relief of the TA11 over the TA31.
Extensively.
TA11H is the best ACOG.
Hammer_Man
03-25-22, 09:57
Extensively.
TA11H is the best ACOG.
TA11H-G is the model I’m looking at. How does the BDC line up out at distance? I plan to mostly shoot M193 and M855.
TA11H-G is the model I’m looking at. How does the BDC line up out at distance? I plan to mostly shoot M193 and M855.
I never took it past 300y on paper or 500y on steel. With M855, it will work very well. I never shot M193 with it, but a run through Strelok makes it look usable out to 400y for sure.
gunnerblue
03-25-22, 13:24
Have any of you used a 3.5x ACOG (TA11) with a 14.5” barrel? I’m building another M4, and I prefer the eye relief of the TA11 over the TA31.
Yes, very much. Shooting 62 gr. Speer and 64 gr. Federal the BDC matches very closely for minute-of-silhouette shooting out to 400 yards (farthest I've taken this particular combo). I also prefer the eye relief on the 11 vs the 31 followed by its little brother the TA33.
Typically late to this party, but 2 TAO 1NSN's and as markm said matching drops to your reticle works wonders. 11.5 and 12.5 6x45 and couldn't be the field of view is for me is the deciding factor
ffhounddog
05-01-22, 06:32
Would a 3.5 TA-11 crosshair made for a .308 work on a 12.5 with m855? Velocity seems close on that barrel length.
davidjinks
05-09-22, 11:14
So my next AR is gonna be a 12.5 inch barreled gun with a carbine length gas system. I’m pretty set on running an ACOG on it. If you go on Trijicon’s website there are tons of 4x options that claim to have the BDC for 5.56. I know that the model the military has used extensively on the M4 is specifically calibrated for the BDC out of a 14.5 inch barrel. Now looking at the ballistics out of a 12.5 inch barrel vs 14.5 inch barrel, there is some loss in velocity but it is not a HUGE loss. I have seen a decent amount of people running ACOGs on 12.5 setups but my question is which 4x option will matchup CLOSEST to 12.5 ballistics? I saw on a livestream Lucas from TREX arms was running an ACOG on a 12.5 and he said he was hitting steel at 400 easy with it, which is all I would expect the 12.5 to do. I’m assuming the model that will match up CLOSEST to the ballistics of the 12.5 is whichever model is calibrated for the bullet drop of a 5.56 out of a 14.5 barrel but I want to know which one specifically? And do they make that model with a green chevron or with any green options? I also was planning on running this gun suppressed full time so I’m assuming I will get some velocity back but not a whole lot. And the majority of the stuff I will be shooting and what my guns are zeroed with is 55 grain XM193. Thanks guys.
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I will only buy the LED version of ACOG. Absolutely the best upgrade they’ve done to this optic. Piggy back or offset RMR and you’re good to go. I like the Horseshoe or chevron reticle. I find the HS to be “slightly” more precise than the chevron, but the chevron seems to be faster for me.
Have any of you used a 3.5x ACOG (TA11) with a 14.5” barrel? I’m building another M4, and I prefer the eye relief of the TA11 over the TA31.
Yes, that's my combination right now. Dead on at 100m and I've made consistent hits on a 8" steel plate at 300m. Mine is the green chevron and my barrel is a Centurion HF 14.5 SOCOM profile.
I'm going to trial it vs. my Aimpoint Comp M4 w/ SIG Juliet 4X and 14.7 Colt pencil barrel. Both are free floated with the same hand guard so it should be a fair match up. To be really fair I should also switch optics and uppers but that would too much sighting in after the switch. I'll test group size at 300m to test the barrels, ease of use and the brightness as seen by my eyes. Already I can say the .5X the ACOG gives up to the Aimpoint/SIG combo isn't a factor due to the brightness of the Trijicon sight.
Just need the time to do it now....
davidjinks
05-10-22, 06:52
Have any of you used a 3.5x ACOG (TA11) with a 14.5” barrel? I’m building another M4, and I prefer the eye relief of the TA11 over the TA31.
LED version, red chevron, pinned 14.5” DD rifle. Eye relief on the 3.5’s are amazing!
I didn’t any real load work ups with the ACOG but it worked well with M193 and MK262.
I have had 2 TAO1NSN'S for a decade or so, in that time I have found that if you take the time to match your munitions to the reticle... you have won the ballistic lottery.
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