The iron sight line is about 2.6" above center of the bore, and the round continuosly goes up (drop = -2.6" at the muzzle, and 0 at 100) from muzzle up to 100 yds... it is impossible to be both zeroed at 100 yds and 3-4" low at 15 yds.Originally Posted by Nephrology
Thanks for the responses everyone.
The rifle was purchased new and these are the first rounds fired. Fixed FSB, the sight is below the level of the base but not buried. It was hitting at the same spot with both the dot and the irons, I have the dot adjusted and POI is within my wobble factor at both 15 and 25y, which is the limit of the indoor range I was at.
I was assuming it was me, until I picked up the other rifle ( also fresh out of the box) and POI was drastically different.
I can get out to a 100y outdoor range next week.
Last edited by TQP; 09-11-2020 at 01:13 PM. Reason: 100y, not 110
'Nobody ever called the fire department because they did something intelligent'
As previously mentioned, raise the front until the base of the front sight is flush with the FSB, then re-shoot. Front sight BELOW flush should result in rounds HIGHER, not lower.
I would NOT shoot it at longer range until you try getting the kinks worked out at 25 yards. Increasing the distance is just going to increase the chance of a shooter-induced issue, and obscure any potential mechanical issues with the rifle. If you're looking for a 100 yard zero, I'd use an "off set" target that you shoot at 25 into a colored circle, then adjust the rounds DOWN to where they should be at 25 yards with a 100 yard zero. Once that's set, move back to 100 and confirm zero.
The other issue I'd ask is, what rear sight are you using? Factory? Is it turned all the way DOWN to 3/6? If not, set it there and re-shoot (though a high rear sight should give high deflection, not low like you're experiencing).
How's the accuracy, POI notwithstanding?
Last thought - what position are you shooting from (standing, prone, kneeling?) Using a sling? If so, what type? Remember, the front sling swivel on the 6920 is attached to the barrel, so sling pressure can affect POI - not 6" at 15 yards, but I'm trying to think of anything that could result in such a radical issue...
Let us know how it goes on the reshoot.
An un-fired rifle, by definition cannot be zeroed. Zeroing is the process of adjusting sights so the Point of Aim (POA) and Point of Impact (POI) correspond at a given distance.
The S&W being "on" was mere luck.
There are various tricks to try and get "on paper" such as bore-sighting, adjusting dots to to correspond with front irons etc but the rifle is not zeroed until rounds are fired. With zeros such as the 50/200 or 25/300 the rifle is not actually zeroed until it is verified at both distances.
Zero on rifles is a living and evolving thing which should be re-verified periodically. Mechanical, environmental and shooter related factors can all effect zero.
Once you have a good zero you may want to place paint pen witness marks on all screws or other attachment points to provide a visual indicator if/when something comes loose.
As noted by Psalms144, different rear sights have their own zero procedures. If your rear has two apertures ensure you are using the small aperture.
As noted bore / sight offset is a thing at close range with an AR. The line of sight is approximately 2 1/2 inches above the bore so you will normally hit low at close range.
Do you know which zero you are going to use ?
There are 3 common zeros for AR's:
25/300 yard as used by the military
100 yard
50/200 yard
25/300 makes sense for the military, especially if you are mostly shooting at longer ranges beyond 200 yards but for CONUS LE and civilian use the other 2 are more practical. I prefer the 50/200 for RDS guns as it allows hits on torso sized targets out to 200 without holds.
Last edited by HCM; 09-11-2020 at 01:36 PM.
Repeat this mantra, “front opposite, rear same”. It will help when adjusting irons. Meaning, front sight gets adjusted opposite of the direction you want to move the point of impact. The rear gets moved in the same direction.
6” low at 15 yd isn’t anything to be concerned with if you haven’t zero’d the rifle. I’d adjust the irons appropriately and move on.
You’ll be low at 15 yds, but how much will depend on your height-over-bore and near zero (generally 1.5-2.5”). This is generally referred to as “height-over-bore” and is something you should become familiar with.
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Homework for the OP:
My eye started twitching while I was watching the kit badger video and he didn’t adjust his sights at 50y even though he was hitting low.
I think (hope) he did it as a demo of how small offsets at close range effect your zero at longer ranges. But, rather than presenting it as an example of deviation throughout the video dude is like “how god of a zero do you really need? There’s something about the presentation that rubs me the wrong way in how I think some folks might take it as thinking a shitty zero is just fine if you aren’t “making head shots on terrorists with hostages”.
im strong, i can run faster than train
Did you watch the whole video ? He goes on to shoot at 200 and also hits low and does just what you mentioned. Uses it as a demo to show how a small deviation at 10 is magnified at 50 and 200. It's between the 7 and 8 minute mark.
The downloadable 10 yard zero target in the video is useful with completely unzeroed guns and/or people who have issues grouping at 50.
I will watch those. Thanks @HCM
'Nobody ever called the fire department because they did something intelligent'
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