Nikon Spot-On app

[KChildress]

What you #1 question is about is where your POI will be at 200 yards when you are zeroed in at 100. At 200 yards it sows your impact will be 1.96 inches low, if you wanted a 200 yard zero you would make your POI at 100 yards 1.96 inches high.

bman940, thanks a bunch for this comment - this helps a bunch.

But I'm still confused with what to do about the two reports above. T_Sabastian picked up on the range clicks being different by 1:2 on the charts. And Nikon is all over the board stating the MOA adjustments. The Nikon website says 1/2" at 200 yd. The literature in the box says 1/4" at 100 yd. And the turrets are clearly stamped 1/2" at 100 yd. I mean, dammit. I guess I'll be using what's stamped on the scope and just assume the Spot On app is calculating the same. But as I see it, even 1/2" at 100 yards doesn't match the clicks stated on either report.

For 200 yd target at 100 yd zero both reports say that's 1.8" low. The Field Reference chart says 1 click. But doesn't that leave me 1.3" from the target? The Ballistics Report says 2 clicks, still 0.8" from the target. I'm not trying to split hairs - or maybe I am - but I don't know how "spot on" Spot On is supposed to be. Do you see anything at all that correlates in these reports?

[KChildress]

Sure way to find out is take it out and give it a try.

Indeed. Will do it.

[T_Sebastian]

Another variable here is going to be your scope height above the bore centerline. It may very well be what is skewing your numbers. I see you have it set at 2.5 which seems a bit on the high side, but I guess not terribly so on an AR type rifle.

I was just reading a discussion on this not too long ago on 2cool (though the discussion itself occurred in 2009)

Which of the following loads is the "flatter shooting load?"

A. Dead on at 200, 7.5" low at 300; 23" low at 400
vs.
B. Dead on at 200, 6.75" low at 300; 21" low at 400

I think we would all say that load B is the flatter shooting load. Agree??

Guess what? The two loads are identical: same bc .287, same mv 3000 fps, same everything, EXCEPT height above bore. The "flatter shooting" load is the one with the scope 3.5" above bore, not the one that was 1.5" above bore.

Again trajectory relative to the direction of the bore is not affected by bore height; however, tracjectory relative to the horizon is affected by bore height.

Take a look at this topic:

http://2coolfishing.com/ttmbforum/showthread.php?t=243035&page=3

[KChildress]

Another variable here is going to be your scope height above the bore centerline.

Good find on that forum discussion. I'm confident with the 2.5" measurement and I definitely saw how the numbers changed when I changed my scope height from the 1.5" default.

[KChildress]

Alright guys, I think I'm almost there. Although the previous Field Reference Charts and Ballistic Reports don't match for number of turret clicks for "X" distance, I'm beginning to think the Ballistic Report may be correct.

But I'm also realizing that I am missing a fundamental understanding of matters involving MOA and turret clicks. If someone could walk me through a couple scenarios, I think I'll be able to solve my problem.

Again, assuming I'm zeroed at 100 yds and for my scope I'm working with 1 click = 1/2" at 100 yds. So that becomes 1.0" at 200 yds? If that is correct, what should we see at 300 yds ... 1.5"? What about 400 yds ... 2.0"?

Finally, knowing that 1 click = 1/2" at 100 yds: If you were to experience 9.0" of drop at 300 yds, how many clicks to dial out the 9.0"? And why, please? Similar scenario: what about dealing with 23.0" of drop at 400 yds?

I appreciate everyone's patience on this! Gotta drive a few hours tomorrow to where I'm sighting the scope so just trying to get it all straight now.

[bman940]

Spot On

I hope this screen shot helps you out. I took my P-223 out yesterday just to make sure all was ok with the data and short of having the exact same bullet, it all worked out. Assuming you are sighting in on a 50 yard target, try to have your point of impact be .76 inches low at 50 yards for a 100 yard zero. I forgot how tough shooting for fine accuracy is with a 3X scope. Also, as discussed, remmeber that your scope is 1/2 inch per click at 100 yards or 1/4 inch per click at 50 yards. Let us know how the sight in session goes.

[bman940]

A pic from my range day here in N. Tx yesterday. Dang hot let me tell you. Make sure you zero the turrets too. Lift up,turn them to zero and push down to lock them in. This will help you if you ever turn dial out your distance or if they ever turn by accident. I always glance at mine to make sure they are where they are suppsoed to be. This scope has easily seen over 10,000 rounds under it.

[T_Sebastian]

Alright guys, I think I'm almost there. Although the previous Field Reference Charts and Ballistic Reports don't match for number of turret clicks for "X" distance, I'm beginning to think the Ballistic Report may be correct.

But I'm also realizing that I am missing a fundamental understanding of matters involving MOA and turret clicks. If someone could walk me through a couple scenarios, I think I'll be able to solve my problem.

Again, assuming I'm zeroed at 100 yds and for my scope I'm working with 1 click = 1/2" at 100 yds. So that becomes 1.0" at 200 yds? If that is correct, what should we see at 300 yds ... 1.5"? What about 400 yds ... 2.0"?

Finally, knowing that 1 click = 1/2" at 100 yds: If you were to experience 9.0" of drop at 300 yds, how many clicks to dial out the 9.0"? And why, please? Similar scenario: what about dealing with 23.0" of drop at 400 yds?

I appreciate everyone's patience on this! Gotta drive a few hours tomorrow to where I'm sighting the scope so just trying to get it all straight now.

Sorry, Im just not much help on this one. I also dont have a good grasp on making calculations for dialing turrets for distance/windage. This is actually one of the reasons I like the BDC reticle. I dont have to dial anything...lol.

How did your range trip go?

[adam_p]

Alright guys, I think I'm almost there. Although the previous Field Reference Charts and Ballistic Reports don't match for number of turret clicks for "X" distance, I'm beginning to think the Ballistic Report may be correct.

But I'm also realizing that I am missing a fundamental understanding of matters involving MOA and turret clicks. If someone could walk me through a couple scenarios, I think I'll be able to solve my problem.

Again, assuming I'm zeroed at 100 yds and for my scope I'm working with 1 click = 1/2" at 100 yds. So that becomes 1.0" at 200 yds? If that is correct, what should we see at 300 yds ... 1.5"? What about 400 yds ... 2.0"?

Finally, knowing that 1 click = 1/2" at 100 yds: If you were to experience 9.0" of drop at 300 yds, how many clicks to dial out the 9.0"? And why, please? Similar scenario: what about dealing with 23.0" of drop at 400 yds?

I appreciate everyone's patience on this! Gotta drive a few hours tomorrow to where I'm sighting the scope so just trying to get it all straight now.

Stop thinking about inches and clicks and do some reading on MOA. It is much much easier.

No counting clicks, no trying to figure out how many inches a click equates. Punch your data into your calculator, look at the MOA correction it takes and dial to that number on your dial.

I does help to know how much a click equates when correcting for misses though. http://nssf.org/video/facts/moa.cfm

[Easttxhunterr]

How do I know sight height when mounting the M-308 with the M-308 mount on a DPMS Oracle ar-10?

[bman940]

Spot On

You measure the scope height mid bore to mid scope and enter that number into Spot On. If you can Chrono the load that is also a great help. Many ammo manufacturer's give an inflated MV. I have found Hornady is about the closest to actual MV then anyone.

Good question and one that certainly will make a down range accuracy difference.

[Easttxhunterr]

You measure the scope height mid bore to mid scope and enter that number into Spot On. If you can Chrono the load that is also a great help. Many ammo manufacturer's give an inflated MV. I have found Hornady is about the closest to actual MV then anyone.

Good question and one that certainly will make a down range accuracy difference.

I found a video of how to do it on a bolt action but what about on an AR platform? How do I determine mid bore?

[bman940]

If you have caliper's you can measure the bore, then measure from the top of the bore to the mid point of the scope and add 1/2 the measurement of the bore. I hope that makes sense?

[Easttxhunterr]

If you have caliper's you can measure the bore, then measure from the top of the bore to the mid point of the scope and add 1/2 the measurement of the bore. I hope that makes sense?

makes perfect sense.