I have a Rock River AR15 .223/5.56. I have only shot it a few times and it hit where I expected it to.

I moved the scope so I took it to Bass Pro to sight it in. I started at 25 yards to be sure it was on paper. The first two shots were touching but low. I adjusted it up the the next two shots were touching but low so I adjusted it up again. The next shot was dead center.

Cool. Now out to 100 yards. I won't be shooting it beyond that much, if at all.

I fired 3 shots. Everything felt solid but I couldn't see the paper. Were they all in the black? Nooooo. They were nicely grouped 7 INCHES HIGH and a tad to the left. WTF!!!

28 clicks down and 3 to the right gave me two shots in the black.

I have no reason to blame the rifle. It groups nicely. I question my cheap BSA scope but at only 100 yards anything should be closer than that - even a Coke bottle with Magic Marker cross hairs.

I was shooting factory hunting ammo. I would expect no more than a 2" drop from 25 to 100 yards but a 7" rise???

What is going on here? How do I fix it?

What is the distance from the centerline of the bore to the centerline of the scope? I'll bet you're around 3", right? If you're accustomed to sighting in bolt rifles with a scope height around 2" or less at 25 and 100, it can be a pretty shocking difference.

FYI, my calculator seems to think that a 3" scope height zeroed at 25 yards will put you 7.2" high at 100 yards.

Sounds like you have a pretty nice shooting scope and rifle combo, there... I think you can fix it by setting it to impact about an inch high at 100, which should put you dead-on at 200.

It's not the bullet drop. What you are experiencing is a sight off-set. Your scope on an AR (typically) is 1.75" over the bore of the rifle. You adjusted your point of impact (POI) to be dead on at 25. So, the bullet is climbing or angled up now at 25 yards. When you moved out to 100 yards, the bullet is still high, and would impact high. You should have adjusted your scope to hit 1.75" low at 25 yards, and you would be very close to zero at 100 yards.

I'm no expert, but your bullet travels in an arc. At 25 yards, it's still on an upward path. At 100yds, it's on its way down. So, if you're zeroed at 100yds, you will actually shoot low at 25 yds. And if you're zeroed at 25yds, you'll shoot high at 100yds.

I think...

Haha, what chad said.

I removed the rear sight so I could mount the scope on the lowest rail reducing the overall height of the rifle.

There is about 2 1/2" from the center of the bore to the center of the scope. Not much more than my bolt rifles.

Thanks Chad. I expected some difference, but 7"? If I was dead on a 25 yards, shouldn't I have been 1.75" high at 100?

I believe that since 100yds is 4x the distance, you would take 1.75x4... Which equals 7.

Here's an estimated drop chart with your 5.56 rifle at 2.5" scope height. If you zero at 25 yards, you should be about 6 inches high at 100 yards. If you zero at 100 yards, you will be 1.49" low at 25 yards. What this is is a simple sight off-set from your rifle. So when shooting at 25 yards, you should have sighted it in 1.5" low at 25, and you would be near dead on at 100. All scoped rifles do this.

25 yard zero
Range Elev
(yards) (inches)
0 ---
25 0
50 2.25
75 4.23
100 5.94

100 yard zero
Range Elev
(yards) (inches)
0 ---
25 -1.49
50 -0.72
75 -0.23
100 0

This is good to know !
I have an AR with a 50mm objective scope so it sits pretty high. When I sighted it in (25yds) I remember this happening but didn't really pay it much attention, just re-zeroed the scope at 100 yds.
Now it sounds like I better learn where it shoots at shorter and longer distances.

THANKS for the info!

No, because you are cranking your scope elevation and moving the zero to 25 yards. The taller your scope is over your bore, the higher you will impact at 100 yards from a 25 yard zero.

You have to remember, the bullet is essentially a straight line from the muzzle to 100 yards (yes, it drops slightly, but for this example, let's just say it doesn't). Zeroing the rifle at 25 yards points the barrel in the upward direction, and the bullet continues to rise. If you want the bullet to impact dead on at 100, then the barrel needs to be lowered to impact at 100, which puts the round low at 25 yards. That's the best I can describe it.

There was a guy on here that posted a video of him trying to shoot a raccoon or skunk with an AR with a night vision scope. The NV scope is mounted pretty high above the bore. He shot, and the round hit right under neath the critter. He posted the video, and didn't know why the animal ran off. It was because of this same reason. He was sighted in at 100 yards, which made the round hit 3" low, which was just under the critter. To make that hit, you need to hold high since the round will hit low. For hunting purposes, you can hold the 2-3" high on a critter from 10-25 yards.

That got through my thick head. Thanks!!! I was not taking into consideration the distance when I set the scope. It helps to have an expert to set the logic straight.

Awesome! Glad it helped!

A lot of shooting matches do this as a stage. They give you a 1" dot at 10 yards to shoot 1 round. My rifle with a 2.25" scope height needs 5.14 mils elevation to center punch the 1" dot. That's the same as a 760 yard shot! So, a 1" dot at 10 yards or a target at 760 yards is the same elevation or hold. It's a simple sight off-set.

Just to be sure I got this right: This rifle sighted in at 100 yards will be about 1.75" low at 25 yards but the same rifle sighted in at 25 yards will be about 6" high at 100.

If I had sighted it in at 25 yards but aimed 1.75" below dead center, I'd still hit the 100 yard target over 4" above dead center. BUT by sighting it in at 100 yards, I'll only be 1.75" low at 25.

Right?

Glad I read this. I was fixing to buy a riser for my FNAR. I have a 50mm objective and I cannot get it back far enough on my rail to get a good sight on it.

donswin, you are making too much of this. Sighting in at 25 yards is just to get you on the paper at 100 and you adjust as necessary at 100. Just sight it in as someone said, about 1 inch high at 100 and you should be good to go. And never again worry about the 25 yard thing.

Reminds me of "The MOA walk back". A stage I've shot three times, at three different matches in LA, OK, and TX. Start at 7 yards on a 1 MOA target printed on an 8 1/2" x 11" paper (that's a .07" red dot), move back to 17 yards, then 27, then 37, ect, all the way to 77. Ya gotta dial impact up to hit those close ones. 7 yard DOPE is the same as 800 yard DOPE if memory serves. Sight offset, as Chad mentioned.

All of this could be avoided if you bore sighted at 100 yards since that's where you want your zero.