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Bore Line versus Sight Line


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This has nothing to do with Benelli, but we have some smart guys in here and I have a question.


Why does an AR-15 (and a lot of newer assault rifles) have sights that are 2 inches above the bore line (i.e., 2 inches above the barrel)?


The answer is NOT because it has a carrying handle. When you get these rifles without carrying handles, the still have sights 2 inches above the barrel. It is also not because they want the sights to co-witness with optics.


The issue with this is....if you zero a rifle at 100 meters and then try to take a precise shot close to your muzzle, you are going to be 2 inches low! A lot of guys in Iraq who had to shoot locks at 10 feet with their M4 carbines missed! They had the right sight picture, but they are shooting too high.


Older rifles like the M-14, M1, all the old bolt guns, etc.. have sights that are as close to the bore line as possible. Competitive shooters also keep sight lines close to bore lines.


Does anyone know?

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The line of sight on an AR-15 crosses at 2 points as with all weapons. The line crosses coming up at 25 meters, and going down at 200 meters. The idea is 1 aperture and "zero" for 0-300 meters on " minute of opponent". The AR-15/M-16 was designed from the ground up as a select fire battle rifle. Shooting 1/2" groups at paper had nothing to do with the design of the weapon. The reason for the elevated sights is the straight thru recoil spring tube design. By its nature it is impossible to get drop in the stock to lower the sights to the bore. Cast left or right is impossible as well. For it to operate as designed it has to be in a straight line with the bolt carrier.


[ 11-25-2006, 10:42 PM: Message edited by: toolman_556 ]

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Thanks Toolman. That makes perfect sense. The higher stock forces you to put the sights higher.


It is interesting, however, that other assault rifles that do not require the stock to be as high still keep the stock and sights higher. Why do you think that is?

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the recoil spring and gas system are either in front of the main receiver or enclosed in it. The garand and M14 have it in front low, the AK is inside the receiver and on top front, the fal is a more shotgun style recoil spring assembly canted downward ion the stock with a benelli style action link. I am not familiar with the sks.... it all depends where you put the action spring and its attitude where the stock has to go. From cheek weld on a garand to line of sight is very similar to an AR-15, at least for me. I am a student of battle weapons. I manufacture AR-15's, I have a FAL, an AK, a garand, a MG-42 parts kit.... I like to see many concepts.

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