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12/21/2007 7:46:36 PM EDT
I am posting this for a buddy who hasn't yet seen the light of being an ARFCOMer.

Anyhow, his AR shoots high...no matter what we do to the sights. The specs:

  • M4 profile RRA barrel that had the fake ban-era flash hider cut off and then was rethreaded right at 16 inches
  • Flat-top with a carry handle mounted

  • F-marked FSB




He has had five different people shoot it to include myself, former force recon marine sniper friend of ours, a current deputy and member of the county SWAT team, his chief of police, and the firearms officer at the department he works at. All of us have it shooting at least four to six inches high when held center mass. All of us have run the back sight all the way down AND the front sight all the way up, to the point where it is going to come out of the FSB. The damn thing shoots high no matter what.

Anybody have a solution? My thoughts are that maybe:

  • it didn't get recrowned right when the fake hider was chopped off?

  • a different carry handle?

  • get rid of the carry handle and try it with a BUIS?

  • get an optic...he will in the future just can't afford it right now



Anyone have this situation or come across this before? Anyone help my buddy?
12/21/2007 8:19:04 PM EDT
[#1]
It sounds as thought the rifle has been in competant hands, so lets assume there is a real problem.  The optic is most likely the best and easiest solution if it has sufficient adjustment!  

You do not mention at what range the 4 to 6 inch high groups are being shot at.  This is a relavant factor.

When looking very closely at the rifle, is there any obvious mis alignments?
12/21/2007 8:21:40 PM EDT
[#2]
Replace the front site post with the appropriate taller one designed for a carbine.

Are you sure this has a proper F marked FSB?  What you are describing is exactly what happens when a non F marked FSB is used.

If you are getting consistant proper groups, just that they can't be zero'ed properly, then try another carry handle before you do anything else.
12/21/2007 8:34:07 PM EDT
[#3]
We have all, even though not shot it together, used a 100yard range.

I don't have the weapon in front of me but will call him tomorrow to verify that it is an F-marked base or not.

I will give another buddy a call to see if we can get his carry handle since he isn't  using it anymore.
12/21/2007 9:35:54 PM EDT
[#4]
Just replace the front sight post with a taller unit (.040 longer from retaining ring to tip of post), no mater what the FSB is stamped.

Bushmaster or any of the vendors sell the taller sight post for around $6, or if you would rather, just get RRA on the phone to see if they will send one for free (it's there barrel).
12/22/2007 7:07:18 AM EDT
[#5]

Quoted:
Just replace the front sight post with a taller unit (.040 longer from retaining ring to tip of post), no mater what the FSB is stamped.

Bushmaster or any of the vendors sell the taller sight post for around $6, or if you would rather, just get RRA on the phone to see if they will send one for free (it's there barrel).


Thanks. Did not know that taller posts were available.
12/22/2007 12:54:23 PM EDT
[#6]
Just checked with him and on the FSB it reads:

F01 RI(inside of a circle) 2


Any thoughts?
12/23/2007 5:04:20 PM EDT
[#7]
Those markings are likely forge markings.  A "F" mark sight will have a "F" stamped on the sight (left side of sight, looking from the rear) after it has been forged and parkerized.

The FSB is likely a standard A2 unit, and as a result, will need the higher post if using a carry handle made for the "F" FSB (Colt, LMT, etc.).  That said, Bushmaster and others make detachable carry handles that will work with a A2 FSB and a std height front sight post.
12/23/2007 6:00:25 PM EDT
[#8]

Quoted:
Those markings are likely forge markings.  A "F" mark sight will have a "F" stamped on the sight (left side of sight, looking from the rear) after it has been forged and parkerized.

The FSB is likely a standard A2 unit, and as a result, will need the higher post if using a carry handle made for the "F" FSB (Colt, LMT, etc.).  That said, Bushmaster and others make detachable carry handles that will work with a A2 FSB and a std height front sight post.


Copy thanks. I've got my buddy borrowing another buddy's bushy carryhandle. Hopefully that will fix the problem.
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