AR sighting in probs (IBSZ) [Update 2006-01-29]

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[ARCHIVED THREAD] - AR sighting in probs (IBSZ) [Update 2006-01-29]

Posted: 1/20/2006 5:06:47 PM EDT

OK. I am frustrated with my sighting-in technique. Having read about the 50 yard zero (that supposedly coincides with a 220 meter zero), sometimes called the Improved Battle Sight Zero (IBSZ). I thought I would try it out. Using an RRA 16 inch barrel, I followed all the instructions, calibrating my elevation sight to 6/3 –4 (6 clicks per number on the elevation dial), then sighting-in with the small aperture in two three shot groups by adjusting the front sight. ( I had already zeroed for windage.)

Supposedly, this would produce groups within a little over 2 inches from POA out to 220 meters, which would be perfect for my normal shooting range. I kept the elevation setting at 6/3 – 4 and continued using the small aperture.

Instead, using new production SA 55 grain military ammo, the groups at 100 yards were POA + 7 inches +. At 200 yards the groups were POA +11 inches +.

I then tried the procedure over with M193 ball. Same result.

Where did I blow it? Or did I?

Posted: 1/20/2006 6:53:06 PM EDT

[#1]

From the IBZ procedure:

"1. Sight should be at 8/3 -2 clicks, that is, all the way down, not up a click. Please note removable handle sights are marked 6/3 (rather than 8/3); also some are in ‘half-clicks’ as well. There should be 3 clicks between 3 and 4 on the knob. If there are 6 clicks then the sight needs to be set at –4 clicks (instead of –2)."

were there 3 clicks or 6 clicks between the 3 and the 4??

only go to -4 if there are 6 clicks between 3 and 4.

if there are only 3 clicks only go to -2.

where were your groups at 50 yards??

they should have been dead nuts on.

By your description they were probably high.

Posted: 1/20/2006 7:08:17 PM EDT

[#2]

There are 6 clicks between the numbered elevation settings, so I recalibrated the "bottom" of the sight to 6/3 - 4 clicks.

My initial 3 shot group was low by about 3 inches, and I had to raise the POI to match the POA. I did this by adjusting the front sight by 7 clicks. At that point the groups were consistently in the 10 ring.

Then I attempted to check the sights at 100 yards and 200 yards, and shot very high (as explained above).

Any further input would help.

Posted: 1/20/2006 7:14:21 PM EDT

[#3]

You are supposed to be -2 not -4

Posted: 1/20/2006 7:19:14 PM EDT

[#4]

I beleive he's got 6/3 sights and not 8/3.

The IBZ varies in it's procedure based on which rear sight you have.

Posted: 1/20/2006 7:22:20 PM EDT

[#5]

Quoted:
You are supposed to be -2 not -4

According to my info (from an article on "theMaryland AR15ShootersSite"), sights with 6 click adjustments between numbered elevations should be at 6/3 - 4 clicks to the bottom when properly calibrated for this method. To wit:

'1. Sight should be at 8/3 -2 clicks, that is, all the way down, not up a click. Please note removable handle sights are marked 6/3 (rather than 8/3); also some are in ‘half-clicks’ as well. There should be 3 clicks between 3 and 4 on the knob. If there are 6 clicks then the sight needs to be set at –4 clicks (instead of –2).'

My sights have the 6 click adjustment. Yes, the handle was hand tightened to the flattop. Please, any other ideas?

Posted: 1/20/2006 7:26:58 PM EDT

[#6]

OK, which brand of rear sight do you have ? I have several detachable rear sights from DPMS that have the 6/3 index drum coupled with an 8/3 sight base thread ! This really messes things up. I'll see if I can find a photo showing the difference.

What I have done with mine is replace the index with an A2 8/3 unit, and then used a Dremel to open the the slot in the sight base thread all the way to the bottom, so that I can get the full 800M elevation with a detachable rear sight. I do the -2 clicks thing and my rifle shoots flat as a pancake out to 250M+.

Posted: 1/20/2006 8:33:38 PM EDT

[#7]

OK, here's where I have to eat a little crow. About 4 or so years ago, not knowing too much about ARs (I used to shoot my SA M1A for DCM/CMP meets), I bought an RRA "tactical" upper to throw on my RRA DCM rifle. At that point I had never used the DCM rifle at a meet and had some extra money in my pocket.

Anyway, I have been using their silly detachable "tactical carry handle" with its integral A2 rear sight.

What I do not understand is if I can reliably put rounds in the 10 ring all day long at 50 yards, (with the sight bottomed out at 6/3 - 4 clicks), then why will that same setting (no adjustments made) shoot so high with the same ammo at 100 and 200 yards?

Posted: 1/21/2006 4:34:12 AM EDT

[#8]

Bump for the day shift.

Posted: 1/21/2006 4:46:32 AM EDT

[#9]

Were you using 6 o'clock hold at 50yds or covering the "X" like this )Y( ?

Posted: 1/21/2006 5:25:05 AM EDT

[#10]

Quoted:
Were you using 6 o'clock hold at 50yds or covering the "X" like this )Y( ?

6 O'Clock hold, shooting at NRA SR-C targets. This is one of the things that make me wonder if this is the answer. The SR-C target has a 13" black (9, 10, and X rings). At 200 yards, the black spot is narrower than the front post. Although I was shooting from a rest under the front handguard, a 6 O'Clock hold is not that easy, but it is better than a center hold for these purposes. It may be that my sight line drifted upward, but I am an experienced shooter (but not with ARs) and not likely to make that elementary mistake.

Perhaps I should be using a sub-6 O'Clock hold to ensure that the sight dies not drift upward; however, I have found that the sub-6 has other problems, including the tendency to shoot lower and lower on the target at greater distances.

It's a puzzler. I was sondering if there was something inherently wrong with the IBSZ technique, but I guess I blew it somewhere.

Edited for spelling.

Posted: 1/21/2006 5:36:21 AM EDT

[#11]

Your sight picture needs to be poi and poa. Using anything but a center hold is no good. The whole point of the IBSZ is to be able to engage targets out to ~250 yards without screwing with the sights. You will not shoot a 6 oclock hold if you are on a 2 way firing range! Rezero it with a true poi and poa center hold and this should get you back in the game. Another thing to consider is minute of man accuracy is for the most part good enough for military application. A fighting gun is for fighting a match gun is for matches. Use them according to their intended purpose.

Posted: 1/21/2006 7:54:13 AM EDT

[#12]

Yeah, slowly it comes to me (and I'm not usually considered too dense). Of course the trajectories will diverge because I had already set them up to do so.

Dumb, dumb, dumb.

I am so used to setting things up at a 6 O'Clock hold on a target range (usually only at 200 yards, with no range changes) I didn't think about the fact that the angle between the POA and the POI at 50 yards would increase the distance between the POA and POI over greater ranges.

In the terms described above, and all other things being equal, then doubling the distance would double the difference between the POI and POA. The fact that the distance was a bit less than doubled could be explained by bullet drop.

Seriouisly, thanks for exposing my ignorance. The next time the temperature gets over 40 degrees I'll be more productive.

I am so dumb.

Posted: 1/21/2006 8:23:40 AM EDT

[#13]

I think that's your answer.

don't use 6 o'clock hold.

now it all makes sense.

live and learn.

get it sighted in and move on.

Posted: 1/21/2006 8:23:48 AM EDT

[#14]

Also sight radius on your 20" match guns will make a difference from a 16" guns sight radius.

Good luck on some decent temps up there!!

Posted: 1/29/2006 6:29:19 AM EDT

[#15]

Okay. I am bringing this thread back because the problem persists.

Yesterday, I revised my sighting-in technique to accord with the comments made above, and there was an improvement, but not to the extent that I wished for.

After sighting at 50 yards with center hold (X ring, SR-C target has a 3” X, group was 1.5”), I shot at 100 yards and 200 yards.

At 100 yards, group was 2” and the declared center of group was 4” above POA.

At 200 yards, group was 5” (with 1 flyer) and the declared center of group was 8” above POA.

All of the above were fired from a 16” barrel (Wilson) using the small aperture of an A2 sight.

Please contrast this with a similar exercise fired from a different upper (20” Wilson DCM/CMP profile) with X rings (1” group) at 50 yards and 3.5” high at 200 yards. Because this is a target upper, I used a 6 O’clock hold.

Ammo was the same, from the same lot. 55 grain American Eagle (Federal) FMJBT.

Any help?

Posted: 1/29/2006 8:02:56 AM EDT

[#16]

im with you bud, i tagged this thread but I dont have any suggestions. I understand why to do the IBZ , with my rear BUIS (wilson folding) I am still confused on how to do it. I zero'd at 50yards and my poa/poi was not too far off at either 50/200 and said thats 'good nuff' but it really wasn't..

Posted: 1/29/2006 8:12:51 AM EDT

[#17]

Quoted:
Okay. I am bringing this thread back because the problem persists.

Yesterday, I revised my sighting-in technique to accord with the comments made above, and there was an improvement, but not to the extent that I wished for.

After sighting at 50 yards with center hold (X ring, SR-C target has a 3” X, group was 1.5”), I shot at 100 yards and 200 yards.

At 100 yards, group was 2” and the declared center of group was 4” above POA.

At 200 yards, group was 5” (with 1 flyer) and the declared center of group was 8” above POA.

All of the above were fired from a 16” barrel (Wilson) using the small aperture of an A2 sight.

Please contrast this with a similar exercise fired from a different upper (20” Wilson DCM/CMP profile) with X rings (1” group) at 50 yards and 3.5” high at 200 yards. Because this is a target upper, I used a 6 O’clock hold.

Ammo was the same, from the same lot. 55 grain American Eagle (Federal) FMJBT.

Any help?

All of the above were fired from a 16” barrel (Wilson) using the small aperture of an A2 sight.

I may be wrong as but aren't you supposed to use the large aperture for close range like 100 or 250 yds.

Posted: 1/29/2006 8:38:44 AM EDT

[#18]

All of the above were fired from a 16” barrel (Wilson) using the small aperture of an A2 sight.

I may be wrong as but aren't you supposed to use the large aperture for close range like 100 or 250 yds.

I guess that range is in the eye of the beholder. I consider the AR .223/5.56 round to be short to medium in range capability. .308 rounds are solid medium range rounds (good to about 800 yards, .308-30-06). Larger (?), non-dangerous game rounds, such as the 7mm Rem, the .300 WinMag and the .338 Lapua and up are long range (in my book).

I was always told that the larger aperture was for short range or low light work. Correct me if I'm wrong.

ETA: I got off topic. I believe that anything under 100 yards is short range. But, knowing that I was going to shoot to 200 yards, I used the small aperture for all of the above for consistency.

Posted: 1/29/2006 11:23:05 AM EDT

[#19]

Quoted:
im with you bud, i tagged this thread but I dont have any suggestions. I understand why to do the IBZ , with my rear BUIS (wilson folding) I am still confused on how to do it. I zero'd at 50yards and my poa/poi was not too far off at either 50/200 and said thats 'good nuff' but it really wasn't..

Thanks for your other reply.

The reason why I'm concerned here is that the IBSZ theory states that ALL impacts should be within 3" of POA between 50 yards and 220 meters.

Comments?

Posted: 1/29/2006 11:49:31 AM EDT

[#20]

I'm really grasping at straws here, I guess I'm tossing this out for consideration.

Just wondering if going to a taller front sight post might help bring the group down a bit. Are you still using your stock front sight? Is it unscrewed quite a bit to get it to zero at 50? If not, I'm wondering if a taller front post would allow you to zero at a shallower bore angle. In theory that would bring down the group some at longer ranges, but again, this is just a WAG for consideration.

Also, I'd check with RRA and see what the elevation adjustment per click is on your rear. You might want to try it with the rear set at say -2 clicks vs -4. I know that what Santos describes for a removable CH sight, but if your elevation screw is a different pitch, that -4 may be too much. Again, just a WAG.

Posted: 1/29/2006 2:55:07 PM EDT

[#21]

So if you are shooting 8" high at 200yds how much difference would 1/4 turn of the front sight make? Then how much difference would that "impact" at only 50yds?

Posted: 1/30/2006 7:40:07 AM EDT

[#22]

Quoted:
So if you are shooting 8" high at 200yds how much difference would 1/4 turn of the front sight make? Then how much difference would that "impact" at only 50yds?

Good question. I will work on that the next time weather allows. (I know the answer in theory, but empirical work is required here.)

Posted: 1/30/2006 7:48:08 AM EDT

[#23]

Quoted:
Quoted:
Were you using 6 o'clock hold at 50yds or covering the "X" like this )Y( ?

6 O'Clock hold, shooting at NRA SR-C targets.

This is your problem. The IBSZ was meant for COMBAT shooting, not DCM shooting. As such you need to zero it with a point of aim=point of impact sight picture (otherwise known as Center-Of-Mass).

Sight Picture should look like this:

Posted: 1/30/2006 7:56:17 AM EDT

[#24]

Quoted:
Quoted:
Quoted:
Were you using 6 o'clock hold at 50yds or covering the "X" like this )Y( ?

6 O'Clock hold, shooting at NRA SR-C targets.

This is your problem. The IBSZ was meant for COMBAT shooting, not DCM shooting. As such you need to zero it with a point of aim=point of impact sight picture (otherwise known as Center-Of-Mass).

Sight Picture should look like this: groups.msn.com/isapi/fetch.dll?action=MyPhotos_GetPubPhoto&PhotoID=nJwAAAIAM6dWGPJgPZ*t0aNCunVYLiIRYShzD!GWPY3T4jKtpEwfO8KrO!*6vLiZHDgxrn2y9dzw

He's holding POA/POI now. he realized 6 o'clock wasn't cutting and he revised his hold, yet the trajectory problems persist.

Posted: 1/30/2006 7:56:23 AM EDT

[#25]

Quoted:
So if you are shooting 8" high at 200yds how much difference would 1/4 turn of the front sight make? Then how much difference would that "impact" at only 50yds?

At 200y the impact would change roughly 4" at 200y, but about an inch at 50y.

BTW for zeroing stick with the small aperture at all ranges.

Ok next question(s). When zeroing (at either range) are you using a sling, sandbags, and/or bipod?

If so is the barrel free floated? If so, are said devices are resting/attached to the free floated forearm?

Posted: 1/30/2006 8:46:47 AM EDT

[#26]

Quoted:
What I do not understand is if I can reliably put rounds in the 10 ring all day long at 50 yards, (with the sight bottomed out at 6/3 - 4 clicks), then why will that same setting (no adjustments made) shoot so high with the same ammo at 100 and 200 yards?

Putting rounds in the 10 ring doesn't say much since we don't know what type of target you are using or how big the 10 ring is. At 50 yards you should be able to put groups reliably in an area the size of a nickle. Are the groups opening up at 100 yards vertically or horizontally or both? To be honest, the sites don't sound like the problem. Doesn't it make sense that regardless of where the zero was, a rifle capable of 1 MOA would still group somewhere on the target? Unless your sites are moving, I would look at the ammo or the shooter. The ammo can be ruled out by mounting a scope and shooting for a group. If it isn't the ammo, then it may be time for a trip to the eye doctor.

[ARCHIVED THREAD] - AR sighting in probs (IBSZ) [Update 2006-01-29]

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