Why was the sight height so tall on the m16?
Posted by RPheralChild@reddit | Firearms | View on Reddit | 25 comments
Just curious it always seemed like an odd choice since all the guns before that in service had a relatively lower one.
ReadyStandby@reddit
It's all about the cheeks.
An AR uses a buffer tube directly behind a reciprocating bolt carrier. Putting all the components in line instead of wrapping the operating system around or setting it near the gas piston.
Being a DI system like this allowed it to run really fast and stay cooler.
But it also means you can't lower the cheek down to the rifle and shoot it properly unless you use taller sights. Since your face will hit the buffer tube.
SnowDin556@reddit
DI really does a lot more for me keeping it from overheating than people give it credit for.
kalash762x39@reddit
Direct impingement does not use a piston. Or maybe I red it wrong but if I didn’t heads up.
TacTurtle@reddit
On an AR-15, the bolt carrier and bolt together act like an inline gas piston - gas goes through the gas tube into the gas key and down into the bolt carrier behind the bolt. This then pressurizes and pushes the bolt carrier backwards away from the bolt head.
"Direct impingement" is a common misnomer for an AR-15 that more accurately applies to a MAS-49 or similar where the gas port blows directly against a flat on the bolt.
ProblemEfficient6502@reddit
The AR-15 isn't direct impingement. It has a piston.
BeenisHat@reddit
Where? The gas goes directly into the bolt carrier last time I looked.
thatARMSguy@reddit
Technically, the bolt carrier is the piston. Gas comes through the gas key, into the carrier, and expands outwards. The bolt can’t move forward cause it’s locked into the barrel extension, so the bolt carrier gets pushed back and pulls the bolt rearwards. It’s easier to just call it direct impingement since that’s a bit easier to understand
Able_Twist_2100@reddit
You've accurately described direct gas impingement.
thatARMSguy@reddit
Direct gas impingement would be the gas vents directly onto either the face of the bolt carrier in the same place a piston op rod would, like certain French rifles, or into a little dead end hole the gas tube sticks into. The bolt carrier expansion chamber on an AR isn’t quite the same
Able_Twist_2100@reddit
I fail to see how the presence of an expansion chamber changes it from a system where the gas pushes directly on the carrier.
BeenisHat@reddit
The MAS-49 works the same way, just without the gas key and rings around the bolt stem.
It's the rearward motion of the carrier, driven by gas pressure that unlocks the bolt. The MAS-49 is a tilting bolt while the AR is a rotating bolt, but it's direct action from expanding gas.
The short stroke piston in a G36 on the other hand, uses gas pressure to drive a piston that strikes the carrier and cycles via inertia. In a Garand or AK, the piston is solidly affixed to the carrier, but no gas touches the carrier. Or enters the receiver.
6ought6@reddit
You are correct,
An the gas key directs the gas into a toroidal cavity behind the bolt which is sealed with the gas check rings in the bolt tail, it acts as a piston for the carrier to receive the energy it needs to move,
Honestly it's incredibly ignorant that folks are down voting you, 1 they have a fundamental misunderstanding of how an AR works and 2 they have the confidence to assume they do
If the gas pushed solely on the key you'd end up with a lot more crap in the receiver as well as goofy misaligned forces on the whole bolt assembly, the point of the direct impingement implementation used in AR rifles is literally to mitigated both of those factors and even use the gasses to help clear debris from the action when firing
Y'all should go watch some small arms solutions and get a better understanding of what the fuck you are talking about.
An oldly but a goody is people online fighting about if an AR is long stroke short stroke or di, specifically because of the internal piston on the bolt head
Accurate_Reporter252@reddit
It's because the straight line system...
https://www.quora.com/What-makes-the-AR-15-so-dangerous
If you look at the X-ray of the AR15, the barrel, the bolt carrier, the recoil buffer and the recoil springs are in one continuous line from muzzle to butt. This helps with recoil, especially on rapid or automatic fire.
Unless you have eyes where your nostrils are, this straight-line stock means you can't get your eyes lined up with sights low on the receiver.
By elevating the sights, you can then see them.
With "conventional" stock set ups, the stock drops behind the receiver which brings your cheekweld down and your eyes lower so you can see along the top of the barrel without elevation. This, of course, means when you fire automatically, the axis of recoil is above your shoulder and the muzzle rises.
https://cdn-fastly.thefirearmblog.com/media/2024/05/15/14069734/x-rays-of-guns.jpg?size=720x845&nocrop=1
That's why the Thompson SMG needed a vertical foregrip and a Cutt's compensator to try and control recoil. The cheekweld was low, the sights were low, the leverage from the recoil force coming back along the axis of the bore was high on or above the shoulder and the leverage against the butt of the gun made the barrel go up....
David_Shagzz@reddit
It’s mainly because the rear sight was a carry handle. Not just a sight. The front sight was made to accommodate for the rear sight height.
edthecat2011@reddit
Carry handle.
6ought6@reddit
The carry handle is a holdover from the early rifles using a charging handle similar to a FAMAS and it needing to be shrouded as to not break off, I've never seen photos with the ar15 specifically with this style charging handle but the Hollywood ar10s with the funky flash suppressors have them,
Konstant_kurage@reddit
Combination of the recoil, height of the comb (check weld on the stock), design necessities and the ballistic arc of the idea cartridge for the rifle at least that’s the ideal answer. The AR is well designed so I’d hope that’s the case.
Cliffinati@reddit
Comb height of the stock and the carry handle
GeneralCuster75@reddit
The carry handle has nothing to do with it. It was only able to be designed into the weapon in such a way because the sights already needed to be celebrated due to the stock.
Wreckage365@reddit
Primarily do the rifle recoils straight back and doesn’t ‘lever’ upwards
0wmeHjyogG@reddit
The sight is tall because of recoil?
I don’t understand the connection.
GeneralCuster75@reddit
Sort of. This guy did a terrible job of explaining that connection.
The sights are tall because the recoil system of the AR-15 is straight backwards, and recoil into the stock, effectively making the stock in line with the barrel.
This is done for recoil mitigation purposes (as well as theoretically potentially aiding in accuracy, but mainly for recoil mitigation) since having the weapon recoil straight into your body removes the fulcrum point that something like a G3 with a stock sloped downward has, which gives the rifle a tendency to climb.
To compensate for having a stock higher on the gun, the sights also need to be higher to align with your eyes since your head will sit higher in relation to the weapon, because of the stock.
So the higher profile sights are not directly, but indirectly, a result of designing recoil mitigation into the platform.
Wreckage365@reddit
To have a straight stock so the recoil is linear, the constraints of the human anatomy necessitate sights raised up off the line of the bore.
The alternative option if you look closely now, you’ll see the stock drops down at an angle to allow a face to look down the barrel. This angled piece makes a lever, where the line of the recoil wants to go straight back, but due to the angled stock it’s going to have much more muzzle rise because of the geometry at play.
TyroneBiggummms@reddit
The buffer tube and stock are where you would need to put your head to see through the sights if the rifle had more classic sights.
ardesofmiche@reddit
The sight height for most rifles is dependent on the stock height. Since the AR15 has a straight line stock for the buffer system, the sights needed to be higher off of the receiver to be comfortable to use
If you measure it and compare most rifles of the time have comparable height sights off the barrel