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View Full Version : Front sight post turned all the way down


evidens83
05-18-2011, 10:06 PM
Is that normal? Took my AR out today to zero. DD A1.5 fixed rear with FSB front. I had to pretty much turn the front sight all the way down just to get it to zero. Looks weird but it did finally get my groupings to where I aimed so thats good right?

dieselpower
05-18-2011, 10:16 PM
what range.

evidens83
05-18-2011, 10:37 PM
25 yards indoor range.

tonelar
05-19-2011, 1:00 AM
That may be as close as you can get. Does the A1.5 have elevation settings? I know A2 do and A1 do not...

On my old CAR i zeroed at 50 and looked over the top of the sight for close up to about 30 yards.

NiteQwill
05-19-2011, 1:06 AM
Zero at 50 yards.

evidens83
05-19-2011, 9:57 AM
^^ I mostly shoot indoors so 25y is what I have to work with :o Just curious. Anybody else have to adjust their post that low?

DougJ
05-19-2011, 10:01 AM
A 25 yd zero is very close, it's not surprising you're bottomed out.

dieselpower
05-19-2011, 10:05 AM
There is something very wrong here.

The post should be 5mm high at the top as measured from the base. I can not see why an A1.5 and Standard FSB would not zero properly.

missiontrails
05-19-2011, 10:16 AM
It almost sounds like what you get when you mix a A2 receiver with a F marked FSB......

evidens83
05-19-2011, 10:25 AM
It almost sounds like what you get when you mix a A2 receiver with a F marked FSB......

Hmmm. It's a BCM flattop upper so :confused:

dieselpower
05-19-2011, 10:26 AM
The F base is .040" higher (at the base of the post) then a standard, which is 1.1MM.

Where did you get this upper / FSB and DD 1.5 rear? Some thing isnt right.

sacshooter1
05-19-2011, 10:30 AM
Don't forget that your point of aim and your point of impact are going to be quite a bit different at that range because the sights are so much higher than the bore.

evidens83
05-19-2011, 10:34 AM
Where did you get this upper / FSB and DD 1.5 rear? Some thing isnt right.

I got both in our used marketplace both from reputable sellers. Supposedly brand new too...

dieselpower
05-19-2011, 10:37 AM
I did a search to see if other where having an issue with the DD A1.5 BUIS..and found your original post http://www.calguns.net/calgunforum/showthread.php?t=414594

so you were 2-3 low, so why did you lower the front post? Lowing the front post raises the point of impact, since you have to tilt the barrel higher to align the sights.

I think there is something wrong with your BCM upper...sorry to say. It happens. The crown maybe chipped and sending the projectile off low.

Maybe its not a real BCM upper....????

Look at the left side of the FSB...is there a "F" on it?

evidens83
05-19-2011, 10:40 AM
Here's a pic of the post:
http://i75.photobucket.com/albums/i307/evalencia83/photo.jpg

dieselpower
05-19-2011, 10:42 AM
Here's a pic of the post:
http://i75.photobucket.com/albums/i307/evalencia83/photo.jpg

That post is the size of a Zulu Spear! No wonder you needed to adjust all the way down... It looks centered to me.

Droppin Deuces
05-19-2011, 10:48 AM
Seems fine to me.

dieselpower
05-19-2011, 10:48 AM
It should be 5mm exposed from the base of the post to the top of the post.

TM9-1005-319-23, section 2, of chapter 2, page 2-55. Its the last link in my sig lines.

if you have to screw it all the way down to get it to center to 5mm...its too dam long. Its out of spec. Buy a mil-spec post.

evidens83
05-19-2011, 10:49 AM
That post is the size of a Zulu Spear! No wonder you needed to adjust all the way down... It looks centered to me.

LOL I'm hoping its the original post. So you say it looks normal? Because whenever I google front sight pictures the post almost always is aligned with the "outer" posts.

dieselpower
05-19-2011, 10:55 AM
LOL I'm hoping its the original post. So you say it looks normal? Because whenever I google front sight pictures the post almost always is aligned with the "outer" posts.

no the center post needs to be 1/2 the size of the outter ones.

please use my last link. go to chapter 2, section 2, page 55.
http://www.ar15armory.com/manuals/TM9-1005-319-23.pdf <--- here

@ 5mm thats a 25 METER installation zero. should be good enough for most work.

evidens83
05-19-2011, 11:18 AM
Thanks for the link. I'll check it out and let you know my findings.

The Director
05-19-2011, 11:31 AM
And by the way, Army zeros at 25 meters all day long, THOUSANDS of soldiers zero their weapons at this range yearly. Don't sweat the range.

evidens83
05-19-2011, 11:48 AM
It measured 5mm exact. Thanks Diesel I am rest assured I zeroed it correctly then. :cheers2:

dieselpower
05-19-2011, 11:58 AM
It measured 5mm exact. Thanks Diesel I am rest assured I zeroed it correctly then. :cheers2:

yeah, its just an "out of spec" post that is way too long.

You are good now.

akjunkie
05-19-2011, 12:11 PM
25 yards indoor range.

Since your limited to a 25 YD range. Maybe this will help. A LEO buddy of mine sent me this link several years back.

http://www.correctionsone.com/products/firearms/accessories/sights-scopes/articles/1335565-Sighting-choices-for-your-patrol-rifle/