Nikon DBC, SpotOn software results confusing

[Subotai]

I'm confused as to the benefit of this reticle. From the looks of this chart, the circles seem useless unless you are at 9x. I thought that scopes would roughly hold zero with any magnification? What am I not understanding?

------ 3.0X 4.0X 5.0X 6.0X 7.0X 8.0X 9.0X
BDC 1- 377 327 294 269 251 237 226
BDC 2- 570 494 440 400 370 345 327
BDC 3- 703 613 550 502 465 434 409
BDC 4- 858 758 685 628 583 545 515
Post - 976 866 787 727 677 635 600

[kcheung2]

Yes most quality scopes will hold zero regardless of magnification, but zero is exactly that - the crosshair of the reticle. You're asking about the BDC marks that are below it.

Nikon scopes are 2nd focal plane so the BDC marks, all those circles below the crosshair, will vary depending on magnification. That's because the BDC marks will subtend a different angular value depending on the magification, whereas with a 1st focal plane scope the BDC marks will subtend the same angle regardless of magnification.

What that means in simpler terms is that with your 2fp scope, as you change magnification, the entire reticle stays the same size. So while you're increasing magnification & zooming in, the reticle doesn't have a corresponding change so what the marks mean varies depending on magnification.

Nikon's system assumes a 100 yard zero. Using your chart, at 3x the first circle corresponds (roughly) with a distance of 377 yards (meters? Don't know what unit you're using) while at 7x it would be a distance of 251 yards. So if you're at the local range & shooting at 300 yards, you would zoom out to 5x, put the first circle below the crosshar (NOT the crosshair itself) on the target, and you should get a hit. Or let's say you want max magnification for 300 yards, then at 9x it almost matches BDC 2 (327), which is the 2nd circle. So put the very top of that 2nd circle on your target.

Or you could get a first focal plane mildot-based scope (which tend to cost more) and, for example, a 300 yard target will always be 1.2 mils (based on the ballistic data I use for my ammo, ymmv) regardless of magnification.

[Subotai]

Wow, that's a clear and succinct answer. Easier than I thought. Thanks!

[bman940]

kch- is 100% on with his answer. Thank you. One of the things I do with my BDC reticle is look for a magnification setting that gives me 200-3---400... yard numbers to make it easier. The number's you show are pretty close to that at 9X. I have a PROSTAFF 5 that is FFP and as kch stated I have no need think about what magnification seeting the scope is on for my shots to be accurate. I have been using Nikon's BDC reticle sccopes for about 10 years now and have taken deer to 600 yards and blown upo for inch jars of tannerite at that same distance. As with any ballistic program, that more accurate the data you enter the more downrange accuracy you will achieve.

[Subotai]

I'm now rethinking the whole BDC thing.

[bman940]

Nikon's BDC reticle really is amazingly accurate once you understand how it all works for you. I am happy to answer any question's you might have about Nikon's scopes,bino's or Spot On.

[kcheung2]

That chart is probably a whole lot of numbers to digest, but an easy way would be to make a small printout & tape it inside the scope cover. Or don't get too caught up in the specifics. The location & size of those markings is not arbitrary. Most people leave their scopes either at min or max magnification, so at 9x the crosshair is 100 yds, the first circle is 200, 2nd circle is 300, etc. For hunting or shooting plates that is sufficient. If you're target shooting at paper then you should choose a different reticle.

As for the advantages/disadvantages of BDC, it's really down to personal preference. There are indeed limitations, but the other option of turning the turrets comes with it's own set of limitations. Conceptually using BDC marks is just a more precise way of doing holdovers. In the past with simple duplex reticles, you knew that to hit something farther away, you aimed a bit higher. How much higher? "A few feet, depending..." The BDC marks take that vague notion and makes it more precise, now you aim to the first circle, etc.