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Posted: 12/26/2003 1:32:03 PM EDT
[Last Edit: 12/26/2003 1:35:18 PM EDT by ad_nauseam]
It is TA11  with donut and BDC for 800 meters.
I have the user's manual but cannot figure out how the BDC feature works.  There are 6 horizontal bars. The manual says that you can estimate distance with it, if the 300-meter bar covers the entire target (20" in width) it is at 300 meters. Same thing for 400m, and so on.  Does that mean that the point of aim is right where that line is pointing?
Link Posted: 12/26/2003 1:41:44 PM EDT
If you look just above this post there is a big thread called The Big ACOG BDC Chart.  You might take a good several minutes and read through that one.
Link Posted: 12/26/2003 7:30:23 PM EDT
Originally Posted By ad_nauseam:
It is TA11  with donut and BDC for 800 meters.
I have the user's manual but cannot figure out how the BDC feature works.  There are 6 horizontal bars. The manual says that you can estimate distance with it, if the 300-meter bar covers the entire target (20" in width) it is at 300 meters. Same thing for 400m, and so on.  Does that mean that the point of aim is right where that line is pointing?
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If you have sighted to the top of the donut at 100 yards and are using the TA11 mounted on a carry handle on a 20" upper with M193 (USGI 55 gr ball) then yes.

Other wise have to check the thread on ACOG and BDC.
Link Posted: 12/27/2003 5:02:38 PM EDT
[Last Edit: 12/27/2003 5:10:44 PM EDT by ad_nauseam]
I was aware of the big ACOG thread.   My question is not about the trajectory, but about the point of aim with the reticle as shown in the manual.

Correction: there are 5 bars in the reticle, not 6. There isn't a 300-meter bar. That's my question, at 300, does the manual tell to aim with the bottom of the "donut"? It is on page 11. You see there are 8 silhouettes ranging from 100 to 800 meters. Look at the 3rd one, the one which correlates to 300 meters.  Only starting at 400m, do you use the 400m bar. It is the 200m and 300m diagrams which are not clear to me.

I know that the trajectory drops about 20" between 100 and 300m (3.75 MOA). The drop between 100-200m is 3MOA. I also know that the "donut" itself is 4 MOA in diameter, according to the manual.

Does that mean I should sight it in at 100m using the top of the "donut", then at 200m expect the center of the donut (or slightly below the center) to be the point of aim, at 300m, the bottom of the donut being the point of aim and at then at 400m, 500m, 600m, 700m and 800m the BDC reticle (i.e. horizontal bars) kick in?

I think I am finally getting it, I just wanted to confirm.

Note: The silhoutte in the manual is 19" in width. Therefore, the 400m bar is roughly 4.75MOA (19"/4).  That makes sense, as it is slightly bigger than the "donut".
Link Posted: 12/28/2003 7:04:07 AM EDT
Top of the donut at 100m, top of the "donut hole" at 200m, bottom of the donut at 300m (though in actual use I've found the bottom of the donut hole is usually closer for me)
Link Posted: 12/28/2003 7:53:48 AM EDT
Originally Posted By Bartholomew_Roberts:
Top of the donut at 100m, top of the "donut hole" at 200m, bottom of the donut at 300m (though in actual use I've found the bottom of the donut hole is usually closer for me)
View Quote


Which ammo / barrel length / ACOQ mounting are your using?

Also have you seen the ACOG BDC thread [:)]
Link Posted: 12/31/2003 7:14:08 AM EDT
That is with a 16" barrel, flattop mount, SS109, and a TA11 sighted 1" high at 100yds.

Part of the reason I use the bottom of the donut hole vice the bottom of the donut (as the manual indicates) is that my range only has a 300yd berm, not a 300m. So the round is hitting 27yds ahead of where the aiming point is calibrated. As a result of both that and slightly different environmental conditions, the SS109 seems to hit a bit higher than the ballistic calculator shows - though on most days, you'd never be able to tell it since user error is about 5x greater than the difference.

My impression that it is hitting higher is just based on the aggregate 30rd groups.
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