Gus, Thanks for the post. I have shot BDC reticle scopes on multiple occasions out to 500+ yards utilizing Spot On to help my accuracy. Nothing like success to make a believer out of you. I have taken many guys to the range who didn't beieve Spot On would work only to make believers out of them. Having an open mind is the first step. Of course I'm not so short sighted that I believe it's for everyone. Check out Nikon's Spot On Ballistic Program and see if you think it will put more meat in your freezer, my guess is it will.

I got a Nikon 'M-223 with the nikoplex reticle and recently sighted it in...I took it to 50 yards and shot about 12 shots to make sure it was hitting where it was supposed to. According to the spot on program it should be 0.6 inches low at 50 for a 100 yard zero, and that is where it was hitting consistently.

I then took it over to the 100 yard range, and I shot three shots (not quickly at all) and after checking paper I was exactly 2 inches high with a group no bigger than a quarter...

I was using a polymer tipped bullet instead of FMJ but still 55gr with approx muzzle velocity as what I had inputted into spot on. Any ideas why I was 2 inches high and not Spot on?

Of course I dialled it down and was hitting fine, but my barrel started warming up and it never hit that quarter sized group again.

spot on program or any ballistic program is only as accurate as the data used in the calculations. Different BC, velocity, scope above bore height... if an are off the output will be off

Barrel twist maybe? Bullet might not have been stable yet. Whats your twist rate?

I have an M&P 15 and the twist is 1:9.

I initially thought the twist ratio might be to blame, but I would think if it was a twist rate issue I wouldn't have gotten the first three shots at 100 within a quarter sized group....seems awfully tight for unstable bullets. It was just weird. Exactly 2 inches high, dead center. And like I said, they were hitting 0.5 inches at 50. Just thought it was strange...

What you or the program have messed up on, is that you should be impacting low at 50 yards. If you want a 100 yard zero then, zero at 100 yards. A 50 yard zero will be almost exactly zero at 200 yards.

For me its +.4 Mil at 50 yards, 0 at 100 yards, and +.4 Mil at 200 yards.

I missed that part in the post right above, but in my first post about this issue, I did mention I was sighting in (and hitting consistently) for a 0.5 inch low hit at 50 yards...according to the program this should have given a zero for 100 yards. But then when I went to the 100 yard range it was 2 inches high for three straight shots, all within a quarter sized group.

Ballistically, this doesn't make sense to me. The only thing I can think is the sight height was way off on the calculator, but I had it set for 2.25 inches above bore. The flight path of the 5.56 55 gr bullet should not rise that fast from 50 to 100 yards. The only other option I can think is maybe the scope was not holding zero when I zoomed. I was shooting around 5-6x at 50 and zoomed to 9-12x when shooting at 100, although I think for that first three group it was all at 12x.

I guess I need to get some shooting done to see if the scope is holding zero with different mag levels...

However, I just played a little more with the spot on program, and I may have been pretty close after all. Looking at the ballistics path for the bullet I was shooting I was pretty close to where it should have been if I was misjudging how far south of the bull I was hitting at 50 yards (even going from 0.6 to 0.35 inches low makes a big difference according to the ballistics path). So, I may have been ok after all. PLan on shooting a little more on Monday, will play with the zoom level and also re-check my zero at 100.

I only have the BDC on My slug gun and it is accurate so far to 200 yds with 2 3/4 slugs. I have a Burris 4x12 that is dang close to 400 yds using there BDC out of a Savage 308.

TheTexan, I love using Spot On for my Browning 20 ga. slug gun. I have shot 3.5 inch broups using 20 ga Sabots in a rifled barrel. Pretty darn accurate and drops whatever they hit like a hammer.

http://i1216.photobucket.com/albums/dd363/bman940/slughunter/spotonslug.jpg

What kind of android apps are available for shooting aids?

Link is two years old; may be more stuff, now.

Nikon has an Android Spot On app: https://play.google.com/store/apps/details?id=com.nikon.spoton&feature=search_result

"Shooter" ballistics for Android and iPhone. It is very, very accurate. You have to pay $9.95, and it is worth every penny! It holds muliple rifles, multiple loads for each rifle, obtains weather data from the nearest weather station to your location and auto populates temp, density altitude, and wind. All of this is dependant on you having a signal, of course. You can turn off the windage and manually enter it. Heck, I turn it all off and manually enter environtmental data from my Kestrel anyway. But the user screens are very, very easy to use. I can't say enough good about this app!