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9/17/2006 2:40:06 PM EDT
I Bought a barrel from a guy at a gun show a few months ago. Im working on building an upper to suit my needs alittle better then the one im currently useing.  

My question is.........

How do I find out if the front sight tower was made to work with a A2---OR---A3 upper?
I have measurment tools but dont know what the measurements of the a2 or a3 are?
Any help would be greatly appreciated, thanks.
9/17/2006 3:22:18 PM EDT
[#1]
If you bought an AR-15 barrel, regardless of size, they all use the standard front iron sight and either the A2 or A3 will work with it. I would go with an A3 flat-top because it will leave alot of options open for you. You can mount a scope, removable carry handle, red-dot scope etc..

Not sure why you're requiring measurements, but the AR15 is such a modular system that everything pretty much will work with everything else. The only bitch is co-witnessing which if you go with an optic should be your only concern. There are different size gas tubes, but on my 16" is one length, and my 20" and 24" rifles they're both the same length. Not sure about SBR (Short Barreled Rifles - they require a special permit to have).

No matter what you use you'll be fine. If you have any more specific questions shoot me an IM. I have 3 AR's and just got done building this one:

9/17/2006 3:48:31 PM EDT
[#2]
Is the front site tower already on the barrel ?
Colt and a few other use a "F" marked FSB for A3 flattops.
If you can't raise the front sight high enough to get it sighted in Bushmaster sells a .40 taller post to use in non F marked towers.
here is a link for the taller post.

Mike
9/17/2006 4:08:33 PM EDT
[#3]
90% of the time it wont matter.  Just try and zero it... if it wont come up high enough, get the bushmaster post.  I have never needed one.
9/17/2006 5:08:51 PM EDT
[#4]
MasterChief-M4
As other posted after you , there is two differnt FSB. Im just being overly anal I belive, from reading the other peoples post.  The diffrance was not very much  but, im going to weld the flash hider on and want the right FSB before doing so. Thank you I to love the modular ability of the AR platform.

That is an awsome rifle, but i needs paintHere



Yes the sight tower is on the barrel, and I would love to avoid buying a new one or removeing this one. Last time I got mad drilled it out and put one in that screws not pins, pins and rivets belong on an AK IMO

I measured some of the other ones I had from the flat plane at the top ot the Sight tower down to the barrel, they were all very close, but it would sure be nice to have the actual spec.

9/17/2006 6:46:53 PM EDT
[#5]
Hey, does that CMore look familiar for some reason???? I think it should but.....
9/17/2006 6:59:46 PM EDT
[#6]
It should
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