I just picked up an ACOG TA11F in trade. I have been scouring the web and found conflicting information about the BDC. Some sources say it is calibrated for M855 with a 14.5" barrel and some say 20" barrel. I understand there are a lot of variables that come into play but what length barrel will work well with this optic? I would like to order a match barrel and I'm not sure if I should go 16", 18", or 20"? I'm leaning towards an 18" White Oak SPR barrel. Can anyone tell me if this combo would work well?
Rifle Scopes Questions about the TA11F
- Thread starter Fatorangecat
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A 16" barrel will probably work pretty well if all you're going to shoot out of it is M855. I had a conversation a few years ago with the Trijicon rep about their BDC reticles and if I remember correctly the TA31F and TA11F reticles were designed around a M855 bullet going slightly faster than what it would be in a 14.5" barrel but not as fast as in a 20" barrel. They felt it struck a good balance when the optic was going to be used amongst different rifles for the military and civilian market. Also, something to keep in mind is that the BDC ranges in meters, so if you're shooting on a range with target ranges in yards it's something to watch as you get past 300 yards or so.
Are you planning to use this on a precision rig of some sort or just an all around carbine? I only ask because you mentioned getting a White Oak barrel and IMO using the ACOG would be limiting the potential of the system if you wanted to use more accurate ammunition down the road.
Are you planning to use this on a precision rig of some sort or just an all around carbine? I only ask because you mentioned getting a White Oak barrel and IMO using the ACOG would be limiting the potential of the system if you wanted to use more accurate ammunition down the road.
I would like a general purpose rifle that is as accurate as I can make it. I agree that a WO barrel could use more optic than an ACOG but I feel like the range of the calibration on the ACOG outperforms the factory M4 barrel.
I will definitely be using better ammo than M855 but I want to stay close to M855 weight and velocity as it is cheap to hoard.
I spoke with Trijicon customer service. The TA11F reticle is for 62gr/M855 with a velocity of 3050 fps on a flat top mount. Based off all the ballistic tables I can find that would be an 18" barrel. I was under the impression that ACOGs were built around 14.5" and 20" barrels but neither will produce 3050 fps with M855. please feel free to correct me as I have not verified any of this at the range.
That pretty much matches up with what they told me a few years ago, the BDC is only to get you close with issued ammo not be dead on balls accurate.
I'm just hoping that I can find a decent 62gr match round that will do well with the optic. I don't expect much out of the M855. I just want it to be close enough that I can shoot surplus ammo. Once I get the barrel and trigger if it shoots well I may upgrade to a variable power optic.
I don't know if I've ever seen a 62gr match bullet, I've seen 52 gr match, 69 gr match, stuff like that. Also keep in mind that if you did find a 62 gr match bullet it is going to have a different ballistic coefficient from the M855 ball round and even if pushed it to the same velocity the BDC wouldn't match up.
I sooooooooooo wish Trijicon (and others like Bushnell) would give more (meaningful) information on their websites. I have collected the following info by spending hours on the net scouring forums, and by emailing Trijicon myself for the first two scopes.
I cannot guarantee the accuracy of this info. Some of it is a few years old. I am sure that Trijicon adjust their reticule subtentions occasionally. For instance, the TA01 used to be based on M193 out of a 20” barrel with the scope on the carry handle of an AR15. If I crunch the numbers below through JBM, they seem to be more consistent with M855 out of a 20” barrel with the scope mounted on the carry handle.
The 200 value of the TA01 was given to my by Trijicon as being 2.6 MOA. That cannot be correct. It would have to be around 0.8 MOA.
The 400 value of the .308 – as I found it in some forum – was given as 5.5 MOA. I left that cell empty because it cannot be correct.
I cannot guarantee the accuracy of this info. Some of it is a few years old. I am sure that Trijicon adjust their reticule subtentions occasionally. For instance, the TA01 used to be based on M193 out of a 20” barrel with the scope on the carry handle of an AR15. If I crunch the numbers below through JBM, they seem to be more consistent with M855 out of a 20” barrel with the scope mounted on the carry handle.
The 200 value of the TA01 was given to my by Trijicon as being 2.6 MOA. That cannot be correct. It would have to be around 0.8 MOA.
The 400 value of the .308 – as I found it in some forum – was given as 5.5 MOA. I left that cell empty because it cannot be correct.
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