The Big ACOG BDC Chart > Optics, Mounts, and Sights

Posted: 11/3/2003 6:06:51 AM EDT

[#1]

Hey JT, I had not run the numbers for a flattop 20" firing M193 because the difference from sighting in per manual was already sub-MOA on the low side.

However, your suggestion of sighting in 0.5" high at 100yds inspired me to run them and you were right. This puts you 0.5" high at 100, dead on at 200, 1" low at 300 and 400, 2" low at 500 and 4" low at 600.

With that sight in, your reticle will cover more of the target than the deviation of the round from the BDC will account for.

Posted: 11/17/2003 9:17:24 PM EDT

[#2]

Bartholomew,
How is this combo? 20" flattop,#19 Acog, TA55,55 Grain Nosler ballistic tip, 24.8 Grains H335. Zeroed at top of chevron at 100 meters. Mostly shooting 300 meters or less. Does the BDC on this scope match my above recipe. Thanks 4weelin.

Posted: 11/18/2003 5:54:49 AM EDT

[#3]

Guys, if you have difficulty figuring out the information for your load based on the information I provided above (how to calculate and where to find online ballistics calculator),
I'll be happy to help anyone figure out these stats for themselves if they will post the results here.

However, I don't have the time or inclination to run the various ammo/mount/load combos myself for all of the members of AR15.com.

4weelin, to determine your info, you'll need to know what BDC the TA55 uses (what mount, ammo and barrel was it designed for), the ballistic coefficient of the Nosler 55gr, and the muzzle velocity out of your 20" barrel with your handload.

Under 300m though with the zero you described, I can pretty much guarantee that you'll strike within the illuminated portion of the reticle without even running the numbers.

Posted: 11/18/2003 4:07:37 PM EDT

[#4]

Bartholmew in your first post you listed flat top 16" 75gr otm at 2615fps W/sight in 2.2high at 100yd.The last post on 3/7 you list the same flat top 16" 75gr otm at 2615 again with sight in as per manual.That makes a differ atleast 2" moa at 100yds between the two methods which is the thickness of the line,correct?I'm confused.By the way thanks again for your efforts.

Posted: 11/18/2003 6:06:36 PM EDT

[#5]

Girad, the 03/07 post is regarding the .308 Acogs, not the .223 Acogs. They have different bullet drop comp lines. This is the reason for the different sight in methods. Thanks.....Chad

Posted: 11/23/2003 1:17:47 AM EDT

[#6]

It took awhile to sight my ACOG but I just love it. Once sighted,it is "simply marvelous". It did take awhile, with 60 clicks left and 64 clicks down. Don't know if it was because I mounted it direct on my flattop RRA upper and if using both eyes reflected the fact that my right eye is stronger. Fact is, at every stage of adjusting until I really did zero, 3 mags always resulted in a silver dollar hole in the cardboard. The last 8 mags took out the black spot in the target with some flyers within 4".

Posted: 11/23/2003 7:24:05 AM EDT

[#7]

Futuredan - I had a similar problem with a TA01NSN on a COlt M4 upper. I have 4 ACOGs and that is the only one that caused an issue, so I dont have any guess as to why, other than it was not mechanically zerod at the factory

Posted: 12/8/2003 3:35:38 PM EDT

[#8]

I'm so happy this thread is here

Posted: 2/1/2004 4:48:32 AM EDT

[#9]

Quoted:
I'm so happy this thread is here

View Quote

ditto

Posted: 2/22/2004 7:17:15 PM EDT

[#10]

any calculations with a 69gr OTM from 16&20 inch ........headed to range now for the velocities
check back
16" 2850fps
20" 2990fps
TA31 T51mt
.301 BC

Posted: 2/23/2004 9:22:31 AM EDT

[#11]

Quoted:
any calculations with a 69gr OTM from 16&20 inch

View Quote

Need a velocity and a BC...

Posted: 3/5/2004 6:57:09 PM EDT

[#12]

With an 18"and 69gr BH i got averages 2773 to 2805.I used 2770 as my average.The java page has me with a 50 yd zero at around 10.2 low at 300yds.I see that Bartholomew has flat top 20" with 75gr otm with same zero at about same FPS with 2750 and its only 1.5 low at 300 yds.How can i be that much worse.Is it that much more momentum with 6 more gr thats the cause?

Posted: 3/8/2004 8:00:20 AM EDT

[#13]

girard - by 1.5" low, I meant 1.5" lower impact than reticle marking for that scope; not that the total drop from the line of sight was only 1.5"

Posted: 3/18/2004 6:41:36 PM EDT

[#14]

How about this one. A TA-31 or TA-11 (donut) mounted on a carry handle with a 20" or 16" barrel. What weight bullet would make the BDC come closer to being yards instead of meters?

Posted: 3/19/2004 3:31:15 PM EDT

[#15]

I have been shooting my 18" SPR with TA11 ACOG with donut and BDC at 100 yards at 5" orange shooting spots.
The rifle was shooting some decent groups but getting the top of the donut to line up with the middle of the orange target spot is kinda of a beech. What is a better 100 yard target for the donut, for getting my 1.7" high 100 yard zero. BTW I have had super accuracy with the White Oak stainless SPR 1/7 twist barrels from Steve at ADCO with the Black Hills blue box 77's. TIA...

AC

Posted: 3/22/2004 5:04:30 AM EDT

[#16]

AC_Doctor, if you can find a target that has a grid on it in 1/4, 1/2, or inch measurements just color off a 4" square target in the grid.

Post the target at 100yds. Now place the donut so it is centered over the square and fire. Use the grid to adjust your sights until they are impacting 1.7" (or whatever the desired number is) above the square.

You can also alternate coloring the grid in 1" sqaures (black or orange) and white 1" squares. By using four white (or black) squares of the checkerboard target as your aiming point to place the donut, you can hit in practically any 1" section that you choose at 100yds.

The same trick with no reference (a 1" square in the middle of a blank page) is harder [:)]

Posted: 3/25/2004 6:04:32 AM EDT

[#17]

Quoted:
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.

View Quote

Just for the sake of nit-picking, because I doubt 1.5" difference in barrel length is going to make a gigantic difference in regards to the BDC:

From the Trijicon website:

"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 are based on the trajectory of the 62 grain bullet from a 16 inch barrel, flattop mount (Picatinny rail Mil.Std.1913)."

Posted: 3/25/2004 1:33:58 PM EDT

[#18]

Bart you are the man! Could you work up a range card for a 11.5" barrel using a Acog Tao1 and Winchester white box " I think it is 55gr."ammo?

Posted: 4/5/2004 7:39:29 PM EDT

[#19]

guys please share your ideas on how should i zero this:

14.5" m4 barrel with 1/7 twist
75 grs hornady OTM moly
acog nsn ontop of a ARMS SIR

available range is 50m max. distance.

please help.

thanks

Posted: 5/1/2004 11:41:40 PM EDT

[#20]

If anyone has run the calculations for the following, I'd greatly appreciate you sharing them:

TA11 mounted on carry handle
16" barrel
M193

Posted: 5/30/2004 9:58:37 AM EDT

[#21]

Anyone have a TA-31F mounted on a 20" carry handle using 69 gr blackhills SMK's ?

Posted: 5/31/2004 7:30:20 AM EDT

[#22]

Anyone have a TA-31F mounted on a 20" carry handle using 69 gr blackhills SMK's ?

If you use the BDC reticle in METERS:

100M: 0 error. This is zro distance.
200M: 1.2" low
300M: 3.3" low
400M: 6.0" low
500M: 7.5" low
600M: 8.1" low
700M: The bullet just went subsonic. You're not going to hit squat
800M: Who are you kidding?
900M: Call in air support.
1,000M: Rent a car and drive closer to the target.

However, if you use BDC reticle as if it indicated YARDS:

200Y: 0.1" high
300Y: 1.0" high
400Y: 3.7" high
500Y: 10.2" high
600Y: 24.8" high
700-1,000Y: See above.

Luck,

SD

Posted: 5/31/2004 9:17:14 AM EDT

[#23]

Thanks alot.

Posted: 5/31/2004 10:46:54 AM EDT

[#24]

One more for you.
TA-31F on a 16" carry handle using 69 gr SMks
meters and yards

I can't hank you enough for the help.

Posted: 5/31/2004 2:02:13 PM EDT

[#25]

TA-31F on a 16" carry handle using 69 gr SMks
meters and yards

Anybody got a velocity for (I assume BH) 69 gr. SMK? All I've got data for is out of my 20". I suppose I could run outside and chrono a few out of a 16" but you all know what a whining bunch of sissies most neighbors are and how they get their panties in a bunch if a guy whips a few measly rounds through the neighborhood.

Posted: 5/31/2004 3:06:50 PM EDT

[#26]

Yes, Blackhills. According to them it's 2850 ft per second but they don't say what barrel length.

Posted: 5/31/2004 4:35:32 PM EDT

[#27]

2,850 has to be out of a 20".

Posted: 6/10/2004 11:21:53 AM EDT

[#28]

Is the TAO1B suitable for flatop mounting on an AR10?

Posted: 6/23/2004 2:02:34 PM EDT

[#29]

Hi Bartholemew ... great work, but...

308 Carry-Handle BDC
This BDC is based on a carry handle ACOG firing M852 Match out of a 20" barrel.
ACOGs using this BDC include the TA11C and TA01B.
Stats used to figure BDC baseline:
M852 traveling at 2,500fps with a BC of .447 and a height over bore of 3.5"
.
.
.snip
.
There is no data for 55gr or 62gr because the .308 BDC is by and large a bad match for these rounds. As you can see the .308 BDC is an excellent match for the 5.56mm 75gr OTM in most applications.

I'd still like to move my 308-reticled TA01B to a flattop 5.56mm CAR w/16"bbl shooting Fed XM193 55gr ammo. I don't wanna have Trijicon change the reticle cuz this scope may end back up on another 308 eventually (FAL).

But it would be nice to know what distances the 308 reticle marks correspond to for 223 55gr XM193/16" bbl, at least out to 400yds (and prob depends if ACOG were zeroed at 100yds or other distance).... can you help us (or point me toward the tools - I didn't see them mentioned in the Forum messages...)

Thanks,
Bill W
San Jose CA

Posted: 7/15/2004 9:00:52 PM EDT

[#30]

" What bullet was used to calibrate the ACOG scopes?
http://www.trijicon.com/faq.cfm
The TA01, TA11, & TA31 (.223) was desinged for the 5.56mm, 20 inch barrel, 55 grain bullet, M16/AR15 carry handle mount. The TA01B & TA11C(.308) was desinged for the 7.62mm, 20 inch barrel, 168 grain bullet, 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 are based on the trajectory of the 62 grain bullet from a 16 inch barrel, flattop mount (Picatinny rail Mil.Std.1913). "

If a TA31 works best on a carry handle of a 20" barreled AR and a TA01NSN works best with a 16" barreled flat top then which ACOG works best on the carry handle of an M4 carbine?

Posted: 8/3/2004 8:32:12 AM EDT

[#31]

Posted: 8/3/2004 9:17:14 AM EDT

[#32]

Posted: 8/7/2004 8:00:37 PM EDT

[#33]

Can TA11 be used on a flattop 20in. barrel without any change?

Posted: 8/8/2004 5:12:57 AM EDT

[#34]

Quoted:
Can TA11 be used on a flattop 20in. barrel without any change?

Yes. That's a combo I use. You will need to develop some field info to correct for the BDC out past about 400 yards. But, quite frankly, one needs to do that for changing climatic factors anyway, even if the bdc reticle were perfectly matched to the rifle/round under one set of conditions.

Luck,

SD

Posted: 8/17/2004 8:03:06 PM EDT

[#35]

Tagged!

Well done sir!

Posted: 10/21/2004 6:50:17 AM EDT

[#36]

Maybe this one needs a web page of its own.

And I know where it could live

Posted: 10/27/2004 10:18:30 PM EDT

[#37]

Bartholomew, read the all the previous post and I wanted to verify what's needed to use a TA31F on a 20" flattop firing M855. I see that you stated it would be withing MOA of the BDC using M193 on a 20" flattop but I didn't see a comment about using M855.

Thanks,
Leadfoot

Posted: 10/28/2004 5:25:11 AM EDT

[#38]

Quoted:
Bartholomew, read the all the previous post and I wanted to verify what's needed to use a TA31F on a 20" flattop firing M855. I see that you stated it would be withing MOA of the BDC using M193 on a 20" flattop but I didn't see a comment about using M855.

Thanks,
Leadfoot

Sight in per manual. You will be on the high side of the BDC instead of the low; but sub-MOA in deviation from BDC.

Posted: 10/28/2004 1:57:39 PM EDT

[#39]

Quoted:
Quoted:
Bartholomew, read the all the previous post and I wanted to verify what's needed to use a TA31F on a 20" flattop firing M855. I see that you stated it would be withing MOA of the BDC using M193 on a 20" flattop but I didn't see a comment about using M855.

Thanks,
Leadfoot

Sight in per manual. You will be on the high side of the BDC instead of the low; but sub-MOA in deviation from BDC.

Thanks for the information and quick reply!

Posted: 11/3/2004 2:34:31 PM EDT

[#40]

I didn't see any sight in info for the compact ACOG's in .223 or 5.56

Posted: 11/4/2004 8:01:30 AM EDT

[#41]

Quoted:
I didn't see any sight in info for the compact ACOG's in .223 or 5.56

Compact ACOG do not offer any BDC stadia lines.

Posted: 11/4/2004 2:10:57 PM EDT

[#42]

Quoted:
Quoted:
I didn't see any sight in info for the compact ACOG's in .223 or 5.56

Compact ACOG do not offer any BDC stadia lines.

Opps... Confused BAC for BDC... my bad...

Posted: 11/14/2004 5:50:58 AM EDT

[#43]

Hey guys,

How well would the BDC stadia lines of say a TA01(not the B model) .223 ACOG track a 147 grain 7.62 NATO round from a 18/20 inch barrel, flattop mounted? Thanks!!!

Posted: 11/15/2004 5:06:01 AM EDT

[#44]

Thanks to ducati650 for the original data and Torf for converting it to a user-friendly viewable format for AR15.com.

www.ar15.com/forums/manageReply.html?a=quote&b=3&f=16&t=210537&r=1675535&page=1

Quoted:
Here it is:
18", SS Douglas barrel, 1:7, CLE Chamber & matching bolt, OPS Inc 2-port Comp. , SPR profile

***
TA31 BDC
height (in) 3.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5
barrel (in) 20 18 18 18 18 18 18 18
vel (fps) 3250 2816 2816 2745 2776 2776 2821 2821
round m193 Hornady Hornady Hornady Nosler Nosler M262M1 M262M1
weight (gr) 55 68 OTM 68 OTM 75 OTM 77 SMK 77 SMK 77 77
BC 0.243 0.355 0.355 0.395 0.34 0.34 0.34 0.34
zero (Yds) 100 100 50 50 50 40 50 45

0 -3.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5 -2.5
50 -1.3 -0.6 0.0 0.0 0.0 0.5 0.0 0.2
100 0.0 0.0 1.3 1.2 1.2 2.3 1.3 1.7
150 0.2 -0.7 1.2 1.1 1.1 2.6 1.2 1.9
200 -0.9 -2.8 -0.3 -0.5 -0.6 1.5 -0.3 0.6
250 -3.3 -6.6 -3.4 -3.8 -3.9 -1.4 -3.5 -2.4
300 -7.5 -12.2 -8.4 -8.9 -9.2 -6.2 -8.5 -7.2
350 -13.6 -19.8 -15.3 -16.0 -16.7 -13.1 -15.6 -14.1
400 -22.0 -24.7 -24.5 -25.3 -26.5 -22.5 -25.0 -23.2
450 -33.1 -42.0 -36.2 -37.1 -39.0 -34.5 -37.0 -35.0
500 -47.3 -57.2 -50.7 -51.5 -54.6 -49.5 -51.9 -49.7
550 -65.4 -75.2 -68.4 -68.9 -73.6 -68.1 -70.2 -67.7
600 -87.9 -97.4 -89.6 -89.6 -96.5 -90.4 -92.1 -89.5

Ballistics normalized to TA31 calculated BDC
TA31 BDC
height (in) 3.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5
barrel (in) 20 18 18 18 18 18 18 18
vel (fps) 3250 2816 2816 2745 2776 2776 2821 2821
round m193 Hornady Hornady Hornady Nosler Nosler M262M1 M262M1
weight (gr) 55 68 OTM 68 OTM 75 OTM 77 SMK 77 SMK 77 77
BC 0.243 0.355 0.355 0.395 0.34 0.34 0.34 0.34
zero (Yds) 100 100 50 50 50 40 50 45

0 0.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
50 0.0 0.7 1.3 1.3 1.3 1.8 1.3 1.5
100 0.0 0.0 1.3 1.2 1.2 2.3 1.3 1.7
150 0.0 -0.9 1.0 0.9 0.9 2.4 1.0 1.7
200 0.0 -1.9 0.6 0.4 0.3 2.4 0.6 1.5
250 0.0 -3.3 -0.1 -0.5 -0.6 1.9 -0.2 0.9
300 0.0 -4.7 -0.9 -1.4 -1.7 1.3 -1.0 0.3
350 0.0 -6.2 -1.7 -2.4 -3.1 0.5 -2.0 -0.5
400 0.0 -2.7 -2.5 -3.3 -4.5 -0.5 -3.0 -1.2
450 0.0 -8.9 -3.1 -4.0 -5.9 -1.4 -3.9 -1.9
500 0.0 -9.9 -3.4 -4.2 -7.3 -2.2 -4.6 -2.4
550 0.0 -9.8 -3.0 -3.5 -8.2 -2.7 -4.8 -2.3
600 0.0 -9.5 -1.7 -1.7 -8.6 -2.5 -4.2 -1.6

Ballistics normalized to TA31 calculated BDC, MOA.
TA31 BDC
height (in) 3.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5
barrel (in) 20 18 18 18 18 18 18 18
vel(fps) 3259 2816 2816 2745 2776 2776 2821 2821
round m193 Hornady Hornady Hornady Nosler Nosler M262M1 M262M1
weight (gr) 55 68 OTM 68 OTM 75 OTM 77 SMK 77 SMK 77 77
BC 0.243 0.355 0.355 0.395 0.34 0.34 0.34 0.34
zero (Yds) 100 100 50 50 50 40 50 45

50 0.0 1.4 2.6 2.6 2.6 3.6 2.6 3.0
100 0.0 0.0 1.3 1.2 1.2 2.3 1.3 1.7
150 0.0 -0.6 0.7 0.6 0.6 1.6 0.7 1.1
200 0.0 -1.0 0.3 0.2 0.1 1.2 0.3 0.7
250 0.0 -1.3 0.0 -0.2 -0.2 0.8 -0.1 0.4
300 0.0 -1.6 -0.3 -0.5 -0.6 0.4 -0.4 0.1
350 0.0 -1.8 -0.5 -0.7 -0.9 0.1 -0.6 -0.2
400 0.0 -2.0 -0.7 -0.9 -1.2 -0.2 -0.8 -0.4
450 0.0 -2.0 -0.8 -1.0 -1.4 -0.4 -0.9 -0.5
500 0.0 -2.0 -0.7 -0.9 -1.5 -0.5 -1.0 -0.5
550 0.0 -1.9 -0.6 -0.7 -1.6 -0.6 -1.0 -0.5
600 0.0 -1.7 -0.4 -0.4 -1.6 -0.5 -0.8 -0.4

Posted: 11/23/2004 1:24:34 PM EDT

[#45]

As a new owner of a TA31F I say THANK YOU Bartholomew_Roberts! EXCELLENT CHART!

Posted: 11/23/2004 10:35:35 PM EDT

[#46]

Lets tack this again!

Posted: 11/24/2004 7:55:10 AM EDT

[#47]

There is no need to tack this thread as it is now linked under the Optics FAQ which is tacked to the top of the page.

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