The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > The Art of the Rifle: Semi-automatics

Reply
 
Thread Tools
Old September 15, 2012, 07:44 AM   #1
zukiphile
Senior Member
 
Join Date: December 13, 2005
Posts: 1,568
Question about AR sight radius and location

Why is an AR front sight located on the gas block rather than the end of the barrel?

I can't see how reduced sight radius is a benefit, yet the ordinary AR design, much like a galil or valmet uses a shorter radius than would be easily obtained by locating the fronts sight out at the end of the barrel.

There must be a reason for this. Could anyone with a spare moment educate me on this?
zukiphile is offline  
Old September 15, 2012, 07:16 PM   #2
Mobuck
Senior Member
 
Join Date: February 2, 2010
Posts: 1,969
Conservation of material and maintaining light weight. Original concept was increasing volume of fire w/o increasing weight of ammo load. Short range accuracy was adequate with the short sight radius. Long range open sight shooters use an extension to increase space between front and rear.
Mobuck is offline  
Old September 16, 2012, 06:50 AM   #3
madcratebuilder
Senior Member
 
Join Date: November 2, 2007
Location: Northern Orygun
Posts: 4,868
There are builds that have the gas block under the hand guard and a non functioning FSB near the end of the barrel.

My last build was similar, gas block under the guard and a LMT front sight on the extended length hand guard. I was trying to work with parts I had laying around and this is what came together.

madcratebuilder is offline  
Old September 17, 2012, 12:02 AM   #4
Justice06RR
Senior Member
 
Join Date: December 21, 2010
Location: Central FL
Posts: 1,187
The AR sight radius is plenty long enough for the rifles' intended use. Remember that there are different types of AR's: Rifle, Midlength, and Carbine, which have different length sight radius.

Furthermore you can always change the sight radius by changing your sights i.e. with a longer rail.

One last thing, you know that an AR15 is not really a sniper rifle right? Its more of your generic battle rifle that can fill many roles
Justice06RR is offline  
Old September 17, 2012, 06:00 AM   #5
LSnSC
Senior Member
 
Join Date: January 5, 2010
Posts: 514
I see some of the guys shooting irons at 3 gun matches with the sight mounted right behind the compensator to get a longer sight radius.
LSnSC is offline  
Old September 17, 2012, 08:49 AM   #6
zukiphile
Senior Member
 
Join Date: December 13, 2005
Posts: 1,568
Quote:
Originally Posted by Mobuck
Conservation of material and maintaining light weight.
I find that rationale completely plausible in a "good enough" for government way. Yet, more sight radius (within reason) will be always be better, and increasing it seems like a low cost improvement for any barrel length.

Quote:
Originally Posted by madcratebuilder
My last build was similar, gas block under the guard and a LMT front sight on the extended length hand guard. I was trying to work with parts I had laying around and this is what came together.
I admire that kind of frugality. It was frugality in part that prompted my question. There are some very pricey FSBs that don't look all that sturdy, while the ordinary front sight moved out to the end of the barrel should do just about as well.

However, I take it that mounting the regular FSB at the end of a barrel can be tricky and take a skill or two.

Quote:
Originally Posted by justice06rr
I see some of the guys shooting irons at 3 gun matches with the sight mounted right behind the compensator to get a longer sight radius.
Does anyone offer this in an upper with a 20 inch barrel? Or is there an easy way for someone with very modest mechanical skills to do this?


This may read like a lot of very stupid questions, so if there is a resource I should be consulting, please feel free to direct me.

Thanks in advance.
zukiphile is offline  
Old September 17, 2012, 10:53 AM   #7
LSnSC
Senior Member
 
Join Date: January 5, 2010
Posts: 514
Replace the gas block and get a clamp on A-2 sight to mount behind comp/ flash supressor. Armalite makes a good clamp on A-2 sight that is popular for this application.

There are some clamp on globe style target sights available as well.

Noveski Offers a Tac Irons upper, and they are the only ones I am aware of.

Im not sure its worth the effort unless you are a competitive shooter, even then , the service rifle shooters seem to be doing very well with the front sight right where it is.

FWIW, I bought a PRI Same plane gas glock for my AR-10 flat top and added a fixed Troy clamp on front sight and DPMS "shorty" A-2 rear. This setup is serving me well. I had no problem hitting steel flashers out to 300 yds at 3 gun match yesterday.
LSnSC is offline  
Old September 17, 2012, 02:09 PM   #8
zukiphile
Senior Member
 
Join Date: December 13, 2005
Posts: 1,568
Thanks for the practical advice. The Armalite FSB looks versatile.

Have you ever used the aperture front sight post?

EDIT - The Levang aperture gets poor reviews, but they don't seem the only ones with the same idea.

Last edited by zukiphile; September 17, 2012 at 02:18 PM.
zukiphile is offline  
Old September 17, 2012, 02:22 PM   #9
chadio
Senior Member
 
Join Date: June 29, 2011
Posts: 641
My front sight is mounted as far forward as possible on the barrel (not the gas block, or the rail, etc.), my rear sight is mounted as far rearward as possible on the receiver. The rifle has a 16" barrel wit a 20.75" sight radius. It may look a bit strange, but it works better for me (especially with the 0.050 front sight post)
__________________
Ex - Navy, Persian Gulf Veteran. Loved shooting the M14, 1911, M60, M2
chadio is offline  
Old September 17, 2012, 06:19 PM   #10
LSnSC
Senior Member
 
Join Date: January 5, 2010
Posts: 514
I use a .045 National Match post I bought from White Oak Armaments.
LSnSC is offline  
Old September 17, 2012, 07:02 PM   #11
Sinlessorrow
Senior Member
 
Join Date: September 25, 2011
Posts: 146
You are over thinking this, I have no issues hitting 300M targets using a standard M4.
Sinlessorrow is offline  
Old September 17, 2012, 07:27 PM   #12
Palmetto-Pride
Senior Member
 
Join Date: May 31, 2009
Location: Charleston, SC
Posts: 1,824
Quote:
Why is an AR front sight located on the gas block rather than the end of the barrel?
I have know idea if this is one of the reasons, but what about the mounting of the bayonet could that be one reason for the FSB being the way it is.

__________________
“The problem with socialism is that you eventually run out of other people's money.”

-Margaret Thatcher-
Palmetto-Pride is offline  
Old September 18, 2012, 06:04 AM   #13
chadio
Senior Member
 
Join Date: June 29, 2011
Posts: 641
Quote:
You are over thinking this, I have no issues hitting 300M targets using a standard M4.
Good for you - however, this thread is not about how good of a shooter you are, it is about sight radius of the AR
__________________
Ex - Navy, Persian Gulf Veteran. Loved shooting the M14, 1911, M60, M2
chadio is offline  
Old September 18, 2012, 01:17 PM   #14
zukiphile
Senior Member
 
Join Date: December 13, 2005
Posts: 1,568


This illustrates an exaggerated application of the idea.
zukiphile is offline  
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 05:37 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2013 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.09375 seconds with 7 queries