This is for someone with a thorough knowledge of the different iron sights for the AR:

I have a problem zeroing my iron sights and have read about the cause.  Let me see if I have this correct:  

I understand that some commercial flat top uppers are built with short Front sight Bases (without the "F" mark on them) that are not made for the A3 flat top Carrying Handle.  This leads to a problem when zeroing the iron sights.  I have this problem.  I have the 0.0833" (taller) Detachable Carrying Handle (Milspec I assume).  I had to adjust the front sight post up until it's almost out of the sight base and very lose before I got close to zeroing.  BUT, because the post is so loose, now I can't retain a decent zero.  Is my thinking correct here?

How many others have experienced this problem?  How many had to buy an aftermarket taller front sight post from Bushmaster?  I think Model1 sales should make good on their product, don't you?

Metzgeri

Edited thanks to Engineer

It seems this issue has been brought up a bunch of times for all manufacturers, but they are older than 30 days, so we can't see them anymore by search.  Here's one Google cache turned up.

To paraphrase: if you have shorter than a 20" barrel and a flattop, you need either an F-marked taller front sight base, or you need a taller front sight post (+0.040") in the your non-F-marked base.  I've never had a problem - I only own one 20" AR15.

PS: I think you mean "detachable carrying handle" not "detachable charging handle."  And, I would make Model1 fix the problem, or at least contact them, for as much as you have spent on the upper.

Engineer2001,
Thanks for the input and correction.  I must have had charging handle on the brain!!  

Ultimately here, I'm trying to get confirmation that the short Front sight Base is my problem.  Then I have a legitimate arguement for model1.

My model1 upper is a 20" as well, no "F mark" on the front sight base and, as I said before, a taller detachable CARRYING Handle.  I say taller DCH because in my search, I came up with the below post that explained a lot.  The search you came up with just let it all flapping in the wind with no real answers.  

http://www.ar15.com/forums/topic.html?b=3&f=118&t=262213

I contacted Model1 and they have to wait to speak to their "technicians" on Monday.  I have fired M16A1's and A2's for the better part of my adult life and never had a front sight post adjust out of the sight housing like this.  I just don't understand it.

Metzgeri

I kinda have the same problem my 16 inch m4gery shoots highat 50 and 100 yards and the front sight is almost all the way up. it has the mark"F01 a circle RI in it then a 2 "on it. It is a RRA upper entry tactical post ban with the bayo lug cut off. The grops are good just a few inches high. EOTECH is going on soon I will rezero and go from there maybe a new taller post could fix zero problem.   J

My Front Sight Assembly just has what looks like a diamond with the number 2 next to it.  No clue what that is.

Your mention of putting an EOTECH on reminds me that I have a bipod (Versa-pod) attached to the lower handguard.  Could that be the culprit?  Could the bipod be forcing me to shoot high and need to adjust my front sight post up and out of the front sight housing to bring Point of Impact down?

Metzgeri

so you installed a carry handle that doesnt work with the front on a low budget kit upper and they should pay?


just get a taller front sight post.

Quoted: so you installed a carry handle that doesnt work with the front on a low budget kit upper and they should pay? just get a taller front sight post.

NO, I spent my hard earned money to buy an AR-15 upper kit from a company with the inferred intent that it work and function properly.  The carrying handle came from the same company and was included in the order.  

Low budget or not, I think any prudent buyer would understand that the rifle should function properly and the front sight post should not have to be adjusted out of its housing to zero.  If it does then it's not my fault for buying the kit from the company, as you suggest.  It's the fault of the company for not offering a product that functions to basic standards.

Metzgeri

have you tried contacting them?

if you're not satisfied then send it back and get something that works out the box

Yes, I contacted them on Friday and they should be getting back to me on Monday (when their technician is back from a show).  We'll have to see what they say then.

Back to the original issue, I have read that this problem has happened to others.  What do you think, am I correct in assuming this is a systemic problem with commercial AR15's.  Have cheaper companies gone with an A2 (shorter, Not "F" marked) front sight on their flat tops that have a higher detachable carrying handle?  Do you know how prevelent this issue is?

Metzgeri