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7/30/2008 12:09:27 PM EDT
I know that the TA31F-RCOA4 is made for 20" barrel, and RCOM4 is made for 14.5" barrel.  Is the normal TA31F made for in between that?
Thanks
7/30/2008 12:25:01 PM EDT
[#1]
TA31F is made for the 14.5" barrel with M855.

HTH,
~Augee
7/30/2008 12:25:43 PM EDT
[#2]
thanks

someone else said it was made for in between 20" and 14.5".
7/30/2008 12:39:10 PM EDT
[#3]

Quoted:
thanks

someone else said it was made for in between 20" and 14.5".


The Trijicon rep I spoke too, and others have said that the F model is the average between the 14.5 62gr and the 20in 55gr BDC, so it would be close enough for both.
7/30/2008 3:04:54 PM EDT
[#4]
I thought the TA31F was made for a 16" barrel.
7/30/2008 3:30:41 PM EDT
[#5]

Quoted:
I thought the TA31F was made for a 16" barrel.


It will work fine on a 16 inch barrel.

There is some speculation that the drop for the carbine models was taken from a 16 inch barrel and not a 14.5.
7/30/2008 5:16:33 PM EDT
[#6]

Quoted:

Quoted:
I thought the TA31F was made for a 16" barrel.


It will work fine on a 16 inch barrel.

There is some speculation that the drop for the carbine models was taken from a 16 inch barrel and not a 14.5.


Your right, it would be hard to tell the difference between any of them for most shooters.
7/30/2008 7:31:50 PM EDT
[#7]

Quoted:

Quoted:

Quoted:
I thought the TA31F was made for a 16" barrel.


It will work fine on a 16 inch barrel.

There is some speculation that the drop for the carbine models was taken from a 16 inch barrel and not a 14.5.


Your right, it would be hard to tell the difference between any of them for most shooters.


Just curious. What does that translate to in inches at 100, 200, 300, etc yards?
7/30/2008 7:51:40 PM EDT
[#8]
Its made for the 14.5 But even the 14.5 works much better on a 16" barrel after 500m
7/30/2008 7:54:49 PM EDT
[#9]

Quoted:
Its made for the 14.5 But even the 14.5 works much better on a 16" barrel after 500m


OK thanks, that clears everything up!
7/30/2008 8:47:46 PM EDT
[#10]
to make it easy:

it's "close enough" for any barrel length/ammunition combo you are using.

if you're shooting sub-MOA groups with an ACOG, and notice that the BDC is off, you should probably buy an even more expensive scope
7/30/2008 9:34:28 PM EDT
[#11]

Quoted:
to make it easy:

it's "close enough" for any barrel length/ammunition combo you are using.

if you're shooting sub-MOA groups with an ACOG, and notice that the BDC is off, you should probably buy an even more expensive scope


Spot on.  - by my calculations you'd have to be shooting within 1MOA at known distances - in which case it's still a pretty arguable point on application - you just don't put an ACOG on one of those, need a target style optic with adjustable knobs for that kind of accuracy.

For shooting at unknown distance, it is extraordinarily difficult to notice the difference between the 20" and 14.5" RCO's (I sure can't), and you won't notice the difference shooting.

Cheers
7/31/2008 11:23:11 AM EDT
[#12]

Quoted:

Just curious. What does that translate to in inches at 100, 200, 300, etc yards?


www.ar15.com/forums/topic.html?b=3&f=18&t=229420

62gr. 5.56mm Flattop BDC
ACOGS that use this BDC are the:
TA01NSN, TA31F, TA11F, TA11F-A

This BDC is based on a 14.5" barrel firing M855 with the ACOG mounted to the receiver via a TA51 mount. If you have one of these, sight in according to manual.

Stats used to figure BDC baseline:
M855 traveling at 2,970fps with a BC of .304 and a height over bore of 2.5"

For a Flattop 20" firing M193:
Sight in per your manual. You'll be within MOA of your BDC.

For a Flattop 16" firing M193:
Sight in at 100 per your manual. You'll be a half-inch high at 300, dead on at all other ranges until 500. At 500, the M193 starts losing juice fast on this trajectory, you'll be 2" low at 500 and 9" low by 600.

For a Flattop 14.5" firing M193:
Sight in at 100 per your manual. You'll be a half inch low at 300, 3" low at 400, 9" low at 500 and 15" low by 550. Once again, the 55gr loses gas fast past 300, so there isn't much you can do here without making your near zero absurdly high.
7/31/2008 11:59:49 AM EDT
[#13]
Thanks for the good info

And also the width of the bottom points of the chevron is 5.3 inches at 100 yards right?  To estimate range?
7/31/2008 12:09:09 PM EDT
[#14]
The BDC of an ACOG is not for precision shooting, it is made to get you hits on a 18” x 20 “ target at midrange distance 300 to 600yds out.

The TA31F’s are setup for a 14.5 to 16” barrel as it have been established, but if you are only shooting out to 400yds you can use any of the ACOGS.  The altitude, bullet weight, and the quality of the barrel will play a big part of the BDC accuracy.  In short you will be Several INCHES off.  

Mike @ CSGW

www.csgunworks.com
[email protected]

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