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Posted: 11/20/2012 4:22:32 AM EST
I've been researching and trying to decide on which ACOG I want to get for my .308. I mostly shoot Federal Gold Medal Match 175gr which is what my rifle seems to like the best. In researching the ACOGs, I saw that Trijicon used 168gr ammo to calibrate the TA01B, however, they don't list the ammo that was used for the TA01NSN-308. I'd heard that it was calibrated for the 175gr per military request. Anyone know for sure?
Link Posted: 11/20/2012 5:07:39 AM EST
I am gonna go out on a limb and say the same ammo is used. Same scope I believe with the addition of the iron sight ring on top
Link Posted: 11/20/2012 5:35:56 AM EST
[Last Edit: 11/20/2012 5:37:49 AM EST by Frens]
I guess the FAQ on their website is not updated

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).


anyway this FAQ is interesting

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 than the MOA thickness of the stadia lines.


so, as long as the NSN-308 was designed for flat top receivers you should be GTG


Link Posted: 11/20/2012 5:40:58 AM EST
Originally Posted By BsChoy:
I am gonna go out on a limb and say the same ammo is used. Same scope I believe with the addition of the iron sight ring on top


All that I've read says that Trijicon used a different ammo.

For their regular .223 ACOGs they used a 55gr bullet but for the .223 version of the TA01NSN they used a 62 grain version to meet USSOC requirements.

For their regular .308 ACOGs, they used a 168gr bullet. The TA01NSN-308 also had to meet special USSOC requirements. From what I've heard, they used a 175gr round to meet these requirements but I can't confirm this.
Link Posted: 11/20/2012 5:47:54 AM EST
Originally Posted By Frens:
I guess the FAQ on their website is not updated

anyway this FAQ is interesting

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 than the MOA thickness of the stadia lines.


so, as long as the NSN-308 was designed for flat top receivers you should be GTG




Thanks Frens! This makes sense!
Link Posted: 11/20/2012 6:10:28 AM EST
dont get crazy about the BDC.
it's just a guide, even if you could use the same ammo/barrel_length/twist/etc used by Trijicon it wont be 100% accurate.
Link Posted: 11/20/2012 7:01:27 AM EST
Official reply from Trijion is that they used 168gr and it's based on the old TA01B. In comparing the two on their website, on difference noted was the TA51 mount on the NSN-308. Otherwise, only difference I see is the reticles and the iron sights.

Hummmmm, only reason I was looking so hard at the NSN-308 is because I thought it at least matched the ammo I was shooting. Thinking it would just be a better fit all around. so now I'm back to square one in trying to figure out which ACOG to mount of my .308.???
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