ACOG Regrets? BDC blues?

ACOG Regrets? BDC blues?

Many of you know I purchased a Ta31F about a year ago. Its been sitting in the safe lately due to my interest in NRA High-Power and all funds (and trust me, i have trouble with funds) going to set up my hodge podge High Power A2. The utility of the ACOG comes from its quick ranging features and the capability to drop rounds on targets at x,y, or z meters away. From what I researched, the Ta31F is calibrated for 62 grain ammunition fired at a velocity of roughly 3000 fps which mirrors a 16 inch carbine. My 20 inch AR15 is not calibrated for said ammo, but I purchased the TA31F anticipating it may go on a 16 inch carbine one day. I still don’t have a carbine. My range doesn’t allow steel core 62 grain XM855 on our steel targets so there goes using the very loading the TA31F was calibrated for!

The stuff you just don’t think about until… DANGIT!

Running 55 grain XM193 loadings in my 20 inch rifle were not matching up with the BDC past the 400 yard steel. I tried it. I had no idea where I was hitting at 500 and 600 yards and I couldn’t hear the steel gongs ring. While the Ta31F is versatile, would I have been happier with a TA01, TA31, or other full-sized ACOG? What tempts me is how easy it is to buy 55 grain XM193 which is the loading used to calibrate all full sized ACOG models unless designated otherwise. Well, the TA31F is designated otherwise.

ACOG 200 yards

BDC woes? Well kind of. Without the right setup, my versatile TA31F wasn’t as versatile. It shot dang high with XM193 at the BDC lines past 400 yards.

Well, if I want to push my rifle, I knew the 55 grain stuff just would not cut the mustard in the wind. I want to run my ACOG in a DMR class one day, so I had to find a loading that matches my TA31F to make it useful. Funny enough, it appears that my 69 grain Sierra match king I whipped up for my High Power A2 rifle works very well with the TA31F BDC.


69 grain sierra match king loaded to 2700 FPS, 59 degrees, .305 ballistic coefficient, with the target at 600 yards.

So If your shooting a 20 inch barreled AR15 on a range distanced in yards with a TA31F, a pokey 69 grain SMK loading hovers right at the BDC all the way out to 800 yards. This setup will shine for longer range shooting since the 69 grain SMK should buck the wind much better than 55 grain ammo. While I wish I did have an Ta01 to easily match Xm193, the Ta31F will likely yeild better results with 69 grain ammo at these distances.  Since I don’t have a carbine at the moment, the TA31F isn’t grab and go easy… but since I found a nice match with my 69 gr SMK I think I will enjoy it much more.

My 600 yard range is closed for winter range updates, and I hope they will be done soon so I can try this out. My ATN 5x gun cam is ready see where the hits are at.

Written by lothaen


  1. Usagi · November 6, 2014

    Funny. Using a TA31F on my 20″ build, shooting M193 clone ammo, it was accurate out to 800. Yes, 800.

    • lothaen · November 7, 2014

      I will have to take it back out and try putting it to paper. At 400 I had to hold low on my steel silhouette and past that I couldn’t hear my hits. I read online that people say it will be within MOA on a 20 using xm193 but I was having no luck at 600. Maybe I was fighting the wind… At 600 yards a 5mph crosswind will dump a 55 grainer over 27 inches…

  2. 509gman · February 1, 2015

    The bdc is only supposed to be minute of man accurate anyway, 800M with an issued 5.56 weapon and ammo is suppressive fire only. If you’re shooting at anything smaller than 20″ it’s gonna give you headaches.

  3. Jagervw · May 20, 2015

    So instead of a ACOG would you now recommend a AccuPoint 1X6 for your 20″?

    • lothaen · May 20, 2015

      The new accupoint with the mil dot stadia would be a good choice. I went with a razor HD and purchased it a few weeks before I found out about the new gear from Trijicon.

  4. Jagervw · May 20, 2015

    I thought that the TA31RCO-A4 would be a good choice; isn’t it for the M855A1 round (62 grains)?

    • lothaen · May 20, 2015

      It is setup for the 62 grain 855 round, and I should have purchased it initially instead of my TA31F, but the TA31F was on sale. I wanted additional magnification and windage adjustments as well so I went to the razor.

  5. BB223 · August 16, 2016

    I’m looking to get another 4×32 ACOG and I’ve got a TA-33 with a red horseshoe (5.56F BDC) that I bought new in December 2014.

    I would straight trade optic for optic if you’ve still got this TA31 and it’s not everything you want.

    If you’ve got an email address and are interested I could send you pics or any info you need or direct you to my listing on M4C forum where I have EE feedback you can see.

  6. Badger · April 19, 2018

    Good stuff tailoring your velocity. But just in case someone finds this doing a search or something & is pondering “which reticle?”…

    Trijicon has a page here with all their reticles:

    Because these (and their off-shoots) are purpose-designed, it is worth time (and YOUR money) to examine & eval what you intend to do with it. Examining the reticles that use the chevron:

    Because it’s what they USE, the mil versions (1 Army, 2 USMC) are currently calibrated for M855 going at the velocity it goes at – the 2 USMC versions are 1 A4 rifle, 1 M4 carbine. Certainly, if the services change their standard ammo, Trijicon will oblige & there’ll be a new reticle coming to an ACOG near you.

    The TA31-F is meant to be a versatile reticle (and, really, we’re talking minutiae in the reticle differences here, way smaller than you can likely shoot). You have to sometimes look in the mirror & ask what you want to do with it. In the FWIW category, if you like XM193, they have a reticle just for that called the TA31-D-100288.

    Also, if you have a TA31-F or one of the RCO’s & like shooting cheaper 55gr stuff, back off a bit in velocity. For example, instead of shooting XM193, shoot Federal’s AE223. The velocity diff in a carbine is going to put it into closer competition with the slower 62gr ammo the reticle was intended for. Or handload your favorite match round as above.

    One last thought: After you’ve done that laser-boresighted look in the mirror, call or drop a note to Trijicon’s tech-support department for ADVICE. They are really good, and really fast in getting back to you – they eat this stuff up.

  7. Beau · September 23, 2021

    Been lookin’ all over for this link, finally found it – AND ITS DEAD! 🙁

    Have no fear! Waybackmachine is here and has plenty of screenshots!


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