I can't be that bad of a shot

[338Shooter]

You are both wrong.

Trust me, it's the Coriolis effect.

I learned this from the movie "Wanted".

No, it is drift due to lunar gravity.

 

[Street Rat]

At 25 yards your scope and barrel are NOT parallel, since the scope is so much higher than the barrel, so the POI and POA will change significantly from 25 to 75 yards. If it is still sighted in at 25, then go back start at 25, then move back maybe 10-15 yds at a time each time readjusting the scope.

I forgot about that, I should have mentioned the scope is sitting on a riser mount not on a carry handle which is not as high, but a little higher had it not been on the riser. Being at that heigth, that would explain shooting higer at 75 yards compared to the 25, correct. Is it best to sight a gun like this at 100yards?

 

[Street Rat]

Worst case scenario if his line of sight is 3" above the bore then he is 9 inches high at 75 yards with a 25 yard zero. That is neglecting gravity.
Kinematics neglcting wind resistance, he should only be 8.045" high at 75 yards with a 25 yard zero and a muzzle velocity of 3200 f/s.

Sighting in at 25 is no different than bore sighting at 25. He should still be on paper at 75 and 100 yards for that matter. At 100 neglecting wind he's looking at 10.3" high. I guess that is enough to miss his target. Needs about 10.75 moa or 43 1/4MOA clicks for a zero at 75 from a 25 yard zero if my math is correct.

That is about how high I was, probably a little higher, taking into account that my yardage is not exact.

 

[POSITIVE DISCONTENT]

Where are you getting this info?

A .223 in the AR platform should not have much more than around 3 inches of change from 0-300yards. If 0 yards is 0 inches then it will be around 3 inches high at 100 yds. 50 and 200 yds will be about the same height. 25 and 300 yds will be about the same height. After 300 it starts dropping really fast.


He is using a 16x20 target at 75yds after zeroing at 25yds. He has other problems.

A scope at 25 yards? I still shoot 250 with steel sights. And I agree with the Doc.....

 

[338Shooter]

I forgot about that, I should have mentioned the scope is sitting on a riser mount not on a carry handle which is not as high, but a little higher had it not been on the riser. Being at that heigth, that would explain shooting higer at 75 yards compared to the 25, correct. Is it best to sight a gun like this at 100yards?

I would sight it in at 100 with the scope. The velocity of .223 will allow the bullet to crest at 100 yards for zero instead of crossing your line of sight twice. That means that from the muzzle to the target at 100 yards you'll never be off more than the distance from the center line of the bore to your line of sight.

 

[mmchambers06]

Even with a ridiculous 3 inches of bore height, I don't see how there could be nearly a foot of variance between 25 and 75 yds when zeroed at 25.

How cheap is a "cheap, cheap" scope?

 

[338Shooter]

Even with a ridiculous 3 inches of bore height, I don't see how there could be nearly a foot of variance between 25 and 75 yds when zeroed at 25.

How cheap is a "cheap, cheap" scope?

Why is ridiculous? It is an AR platform Everything I read they average 2.5" from bore to line of sight. If the OP would measure from the center of the bore to the center of the scope it would clear this issue up. If it is in fact 2.5-3" then my numbers are correct. And I have verified the calculations by the calculator I've posted above by another less functional calculator on Hornady's website.

I don't mind that you guys don't agree with me, but how about facts and numbers instead of conjecture?

 

[mmchambers06]

The .223 will rise before it falls. It does not start at one height and go down.

Flight path of a 55gr. .223---0" at 0 yds. (duh), around .5" high at 50 yds., 0" at 100 yds. Then it starts dropping below the line of the bore.

Here are the ballistics with a 1 yard zero to 300 yards. Impact is in inches.

You can't zero at 1 yd. If you trying to find the trajectory relative to the bore, punch 0 for sight height into your calculator.

Anyway, my guess is that the OP zeroed at closer than 25 yards. The closer the zero, the worse off the POI will be downrange.

 

[mmchambers06]

I don't mind that you guys don't agree with me, but how about facts and numbers instead of conjecture?

Not conjecture.

Chill pill, homie. My calc says 5" high at 75 yds. with a 25 yd. zero and 3" sight height. He should be on paper more. Again, sight height could be way off or he zeroed closer than 25 yds.

 

[Spiff]

I would sight it in at 100 with the scope. The velocity of .223 will allow the bullet to crest at 100 yards for zero instead of crossing your line of sight twice. That means that from the muzzle to the target at 100 yards you'll never be off more than the distance from the center line of the bore to your line of sight.

A 50/200 yard zero is about the best compromise for a .223 rifle. You'll be (approximately) plus or minus 2 inches from point of aim to like 250 yards, I think. Dead on at 50, and dead on at 200 again.