Armory Sponsor
Posted: 9/24/2014 11:52:11 PM EDT
|
So after a long range day, my dad and I were sitting at home figuring out how many clicks we need to rise in elevation for X number of yards on our M1A. We then became horrifically confused as to whether you raise or lower the rear sight. After hours of banging our head against every wall, table, and door in the house, he finally convinced me that he was right and I was wrong. The next day, I decided to see how stupid we were and asked all the guys in my battalion to see if they knew... assuring that I am not the only moron on the surface of the earth (they were wrong too). It has turned into a week long debate (even though I now know the answer) with my friends still trying to convince me I am wrong. So I figured I would ask the same question on here and see what comes of it.
Question: If you are trying to zero in a rifle, specifically an M1A, and the rounds are hitting low of you point of aim, do you raise or lower the rear sight? Those who are familiar with M1As or M1s might have more insight to this and understand what I mean by raising or lowering the rear aperture. I don't want to share my opinion for two reasons: I want to get your original thoughts, and if I actually am wrong, I don't feel like even more of a moron. If anyone has any way of explaining this clearly, please share so I can spread the knowledge and put this debate to rest. Thanks! |
|
A rear sight you move it the way you want it to go. So you will have to RAISE your rear sight to have a higher point of impact.
It might be confusing because when you zero an AR or M16/M4 with the irons. You set the rear iron sight to where it should be, then you adjust the front sight for your point of impact. And then you do it opposite because it's the front sight. Front sight you move opposite of the way you want it to go. If you want to raise the point of impact, you lower the front sight. But you can't do this with an M1A without filing the front sight, so..... RAISE your rear sight to RAISE the point of impact. Just picture in your mind what the barrel is doing, in an exaggerated way. If you're raising the rear sight, the front of the barrel has to raise up to meet your line of sight, therefore pointing more upward, therefore having a higher point of impact. |
|
Imagine your front sight is 6" higher than the rear. When you make your rear sight level with it, you're going to have to lower the muzzle towards the dirt. This puts the bullet impact low. Imagine your rear sight is 6" higher than the front. Sighting through them will require you to raise the muzzle towards the sky. This will raise your point of impact. Thus, raising the rear or lowering the front will raise your bullet's impact. Lowering the rear or raising the front will lower the impact. What confuses people is that the AR front sight is marked "Up" and "Down", but is referring to the bullet's point of impact, not the direction the sight post is travelling. If you want to raise the point of impact, you turn the post in the "Up" direction--but in actuality, you are lowering the post when you do this. I always thought this made things more confusing than necessary and wished they would refer to the sight's direction of travel instead. |
|
Thank you all. Surprisingly, after explaining all of this in clear detail, there are still people saying that I am wrong. Just to be clear, we did go to the range, and had no issue zeroing the rifle. It wasn't until later that night that we became a bit confused on which way to adjust the rear sight to raise POI. For some reason, all the manuals we have, including original US Army and Marine Corps manuals don't clearly state whether the rear sight moves up or down.
I think the primary confusion is that some don't understand that zeroing a rifle means adjustin the sights until POA and POI are the same. They only think of hitting (or aiming at) a bullseye. My peers are only thinking of where they're aiming and forget about where the muzzle is pointed; hence their belief of lowering the RS will bring the rounds up. Not to mention their confusion caused by M16/M4 front sights (moving the front sight toward "UP" direction actually moves it down). Once again, thank you for confirming this. The acronym of FORS helps out a lot. |
Try showing them these rather terrible photos I took.  The M1903 illustrates FORS really well because the rear sight is so huge. Just focus on the small aperture sight, not the triangle or the notch at the very top. This is sighted to a distance of maybe 400-500 yards or so (I didn't check). It's hard to see, but the front sight is squarely within the aperture.  Whereas this is set for a much longer range of over 2300 yards.  Obviously, I would have to raise the muzzle, and thus the point of impact, quite a bit to get the front sight visible in the aperture. Here's what that looks like from a side view. The cleaning rod is a straight line from the aperture.  And here's how far I'd need to raise the muzzle to get the front sight into the rear aperture.  |
Armory Sponsor