Trijicon TA01NSN Zeroing

[Jack_Bauer]

What is the recommended zeroing yardage for a Trijicon ACOG TA01NSN on a Colt M4 with 11.5" & 14.5" barrels with M855 ammo?

[ICANHITHIMMAN]

Dont you have the manual, its in there it says 100meters with the 14.5" its not ment for the 10"

[JSantoro]

http://www.trijicon.com/na_en/support/faq_ACOG.php


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).


So, 14.5" 1-in-7" barrel w/M855 = zero @ 100meters using the 100m aimpoint (primary crosshair). You can do a grouping exercise using the 300m aimpoint @ 25m to put you on paper @ 100m.

You should be able to chart out, to a certain degree, what difference the 11.5" barrel will produce if you know the MV of that round out of that barrel and factor for a 2.755" optic height-over-bore.

Sorry, I don't have a specific answer except to say that the optic isn't specifically designed for an 11.5" barrel length, so while you can still zero to 100m, the BDC will not match.

[Jack_Bauer]

Thanks guys. With that said what type of Trijicon scope you you recommend for a 11.5" barrel?

[Failure2Stop]

I find that a soild 300 meter zero on the 300 meter aim point tends to give a more consistent application of the BDC accross all ranges, especially when deviating from the design criteria.

To get the best indication of trajectory of your given conditions, plug the data in to decent ballistic calculator (such as the JBM, which I tend to use a lot) compared to design trajectory

Personally, I don't recommend the ACOG line for anything unless the user demands one.

[JSantoro]

Hooo...!

There isn't one designed for that recipe, but I'd actually say stick with what you have, as the BDC still provides reference points for KD.

For example, the Corps uses the TA31, also supposed to be zeroed @ 100m, but the KD qual is on a range set to yards, so instead of (insert tired old rant, here!)....they came out with a data book that shows, for example, the vertical offset hold one uses in relation to the 500m line IOT make a center-mass hit on a 500yd target.

So, short of going with a 4x fixed or a 1-4x variable with a mil-dot or similar reticle that's generic and not barrel/ammo specific (check the stickied thread about 1-4x variables, and search for other, similar threads)....

...the answer is to shoot the piss out of your TA01 on the short gun at KD so you get to know where it prints in comparison to known reticle references, then take it and shoot more piss out of it again at unknown-distance to confirm your KD findings.

There's also futzing around with different ammo types at KD to see if there is a load (hehe I said "load") that makes up for the shorter barrel.

Either are time/round-intensive, so I think a non-BDC reticle is a better answer, unless one finds the idea of experimenting fun and worthwhile.

EDIT: Pay attention to the recommendation RE: 300m. If one has the facility and the wherewithal, it's a more sound jumping-off point.

[Jack_Bauer]

I think with all that said the TA01LAW might be better sited for both my barrels.

[a0cake]

Okay man, here is what your ACOG's subtensions break down to:

100 meters – zero

200 meters – 1.4 MOA

300 meters – 4.0 MOA

400 meters – 7.4 MOA

500 meters – 11.6 MOA

600 meters – 16.8 MOA

700 meters – 23.3 MOA

800 meters – 31.4 MOA

Run your load (haha I said it too) through a ballistic calculator and determine the offsets from the chart above. Adjust accordingly.

I personally hate all things BDC. Give me a good MIL reticle with matching MIL adjustments over a BDC any day. To each their own, but most experienced shooters eventually graduate from the BDC vice. Just my opinion, please don't have a conniption if you like BDC's and fancy yourself an expert.

[Dennis]

I have had a TA01NSN for many many years on a few different 14.5" carbines and even with a 25Y zero on the 300Y line with AE 55gr ammo I have no problem hitting chest sized steel to 400 and even 500Y. A 100Y zero is better and a 300Y even better than that but if you only need minute of asshole accuracy then it works great.

Unfortunately, my standard SD BH75 loads don't line up as well but a bit of known holdover works fine for the same MOAss accuracy, which with 4x at 300+Y seems all that the ACOG is meant for...

Dennis.

[JSantoro]

Derp-derp: You should zero it at 100yd.

Shooter: But the manual says that the reticle is scaled in meters, so shouldn't I measure out 100m?

Derp-derp: They're the same thing.

Don't be a Derp-derp.

100m = 109yd
1000yd = 91.4m

THEY'RE NOT THE SAME THING, so stop passing bad gouge by insisting that they are.

Jezus....

[Dennis]

I apologize if I came off as recommending using yards as opposed to the correctly specified meters. I was only relating my experience given what I have to work with, a range in yards and the most available 55gr ammo. The range actually lasers out to ~103yds at the 100y line and is a bit off on the high side depending on your target farther out. I would think that most shooters ranges in the US would be in yards as well...

So my point really was that the reticule has always worked surprisingly well for me in this not-exactly-as-specified instance and that my 4x ACOG reticule works great for less than precise targeting.

Dennis.