ACOG BDC

[m1a1driver]

got an acog rco m4 i know the bdc is calibrate for a 14.5" you think a 14.7" barrel will make any difference? I dont think so just thought id ask. I heard a 16" will shoot a bit high at distance

[PrimaryArms]

got an acog rco m4 i know the bdc is calibrate for a 14.5" you think a 14.7" barrel will make any difference? I dont think so just thought id ask. I heard a 16" will shoot a bit high at distance

No it will not

-Dimitri

[Press Check]

I have a 16" barrel, and the BDC remains spot-on. The ammo I use has more of an influence than the barrel length does.

[SuperSet]

It's a shame that Trijicon doesn't publish their BDC subtensions, like other optic manufacturers. That way you can easily figure out how your ammo and velocity matches to the reticle. ACOGs have been out for years now.

[mrvash]

What type of ammo is to be used for the BDC calibrated for the 5.56/.223?

[SuperSet]

From Trijicon FAQ:

03. 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).

[sunborder]

ACOG subtentions are out there if you look hard enough for them.

[PrimaryArms]

ACOG subtentions are out there if you look hard enough for them.

+1 ask Isterlok


-Dimitri

[sunborder]

If it really burns you, you can always call trijicon. They have been pretty good about confirming ballistic callibration data (fps, bc, weight, optic mount position) and BDC subtensions.

[SuperSet]

I have. They gave me the answer posted on the FAQ.

[SuperSet]

Maybe you could post them up so others can easily find them also.

[glug]

Let's put this in perspective--

A rough rule of thumb is 1" of barrel ~ 50 ft/s of muzzle velocity.

So a 0.2" barrel length difference you are looking at less than 10 ft/s difference. That is totally in the noise of normal muzzle velocity variation from round to round even with good ammo.

No, it will make absolutely zero difference.

[sunborder]

Maybe you could post them up so others can easily find them also.

These are the numbers I've been using. I'm pretty sure they're second-hand, but I don't recall exactly where I got them, since it's been a couple of years. I seem to recall that the guy said he got it directly from Trijicon. I've heard a number of people say the same thing for different optic models, so not sure why they were unwilling/unable to give you better information.

This is for the TA-31f (A4 type, not M4):

100--0 MOA
200--1.3
300--3.8
400--7.1
500--11.2
600--16.4
700--22.8
800--30.8

[PrimaryArms]

What round is that?

[PrimaryArms]

These are the numbers I've been using. I'm pretty sure they're second-hand, but I don't recall exactly where I got them, since it's been a couple of years. I seem to recall that the guy said he got it directly from Trijicon. I've heard a number of people say the same thing for different optic models, so not sure why they were unwilling/unable to give you better information.



This is for the TA-31f (A4 type, not M4):



100--0 MOA

200--1.3

300--3.8

400--7.1

500--11.2

600--16.4

700--22.8

800--30.8

What round and fps?