ACOG question - BDC reticle

E

edon

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On the EE there is an ACOG TA31F which has a BDC calibrated for a flattop. What change in point of impact would be noticed if the flattop adapter was removed and it was bolted on a A2 carry handle instead?
 
....What change in point of impact would be noticed if the flattop adapter was removed and it was bolted on a A2 carry handle instead?
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There is more to it then that, it's also calibrated based on barrel length and ammunition type. You will likely not get it to match your setup.

I run a TA-11 and I use my own range values for the statia lines not those indicated.
 
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Yup. In order to for the BDC hash marks on the reticle to work for you, you'd need to be running the same length barrel (probably either a 14.5" or 20") and the same weight bullet (M855 is a 62 grain bullet). Check the specs on the Trijicon website to see which barrel the BDC on a particular model of ACOG is set up for.
 
FYI Trji's mil reps admit the website data is a bit erroneous.

The TA31F is actually calibrate for a 16" bbl (they split the dif between the 14.5 and the 20

The TA31RCO-A4 - is calibrated for the 20" bbl with M855
the TA31RCO-M4 is for the 14.5 w/ M855

All on the Flatrop TA51 mount on a Colt flattop (if one is being picky)
 
Thanks for the update, guys. I was thinking of the TA31RCO A4 and M4. I didn't know that Trijicon had split the difference on the TA31F.

I guess that's the difference between being an amateur enthusiast and a professional :)
 
So the factors that affect the BDC are only barrel length and bullet weight/energy? Height above center of bore doesn't change anything (within reason, of course)?
 
Height above bore does play some part.

Bullet trajectory -- and how close it compares to the BDC reticle is the issue.
You can mix and match some combo's to nearly aproximate another data value.
i.e. 77gr Mk262 out of a 16" can mimic the data for a 20" M118LR 308 to a certain point etc.

www.ar15.com has an excellent thread by Bart Roberts on the ACGO reticle --- its very informative
 
KevinB said:
Height above bore does play some part.

Bullet trajectory -- and how close it compares to the BDC reticle is the issue.
You can mix and match some combo's to nearly aproximate another data value.
i.e. 77gr Mk262 out of a 16" can mimic the data for a 20" M118LR 308 to a certain point etc.

www.ar15.com has an excellent thread by Bart Roberts on the ACGO reticle --- its very informative
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What's an ACGO ? :D
 
I believe it is "Advanced Combat Optical Gunsight". As for the earlier question - the reticles for the ACOGs are calibrated for a specific load (i.e. TA01NSN - 62 grain at ###X FPS) but as well Trijicon also takes into acct the height above the bore that the scope is supposed to be mounted. That being said I had a TA01 and have a TA01NSN. The has marks are pretty close for most loads (until you get further out) and 4X doesn't give the precision that would let a shooter take advantage of 1" difference in where the has mark are. I found the ACOGs to be pretty much bang on with most loads and the ones that weren't I could figure out what distance the has mark was good for..
 
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