Typically it's the 10X magnification setting, though we've seen scopes that use 12X as the default zoom level (and much lower settings for scopes that don't zoom up to 10X), so it's best to check your manual or contact the manufacturer to be sure.

Often times this setting is referred to as the Mil-Dot Ranging Magnification or Mil-Dot Ranging Zoom Level.

First, let's start by going over the proper terminology for the two pressure results which are pertinent to shooting:

• Station Pressure - a.k.a Uncorrected Pressure, or Absolute Pressure - this reading does not take altitude into account and at higher elevations will generally be lower than sea-level readings.
• Barometric Pressure - a.k.a Corrected Pressure, or Sea-level Pressure - this reading takes into account the current altitude and so long as weather conditions are similar, will generally provide readings equal to that of sea-level. This is the type of reading reported by the National Weather Service and other weather reporting agencies and services.

iSnipe currently computes using Barometric Pressure which is then corrected using your altitude (manually entered or retrieved via GPS).

In iSnipe v3.0 and up, we've included ballistic coefficients that were measured by a ballistician named Bryan Litz. Bryan has written an excellent book that helps explain the complexities of modern ballistics in terms that us "mere mortals" can understand. The book is titled Applied Ballistics For Long Range Shooting and along with the wealth of information, included are 175+ expertly measured Ballistic Coefficients using the G7 drag model.

If you'd like to access the actual numerical values for these B.C.'s please purchase Bryan's book, so that you may better understand the data you're using as well as gain a better understanding about modern ballistics in general. We don't gain anything by endorsing Bryan's products, we just strongly believe that all long range shooters should read his book at some point or another.

In previous versions of iSnipe ( > v2.3.4), iSnipe would process all ammunition when first launched. If this process is interrupted, and you're left with an incomplete database, simply re-install iSnipe™ using the following procedure:

• Optional: If you have created your own profiles in iSnipe™, first use our web-backup feature to save your profiles to our server.
• Delete iSnipe™ from your device.
• Attempt to repurchase iSnipe™ from the App Store app on your device. You will be alerted that you have already purchased this item and will be asked to re-download it instead. Select yes (you will NOT be charged again).
• Once iSnipe™ is reinstalled, verify that all the factory loads are there.
• Optional: Run the web-backup feature again, this time selecting 'Download Profiles' to pull your saved profiles back down to your device.

Currently iSnipe™ is supported on the iPhone, iPad and iPod Touch, with no plans to develop for other platforms in the near future. We have been looking at a few alternative platforms for a while now, but still have not made any decisions one way or another.

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Most ammo manufacturers publish their ballistic data using the G1 drag function or drag model. There exists several drag models though (G1, G2, G5, G6, G7, G8, GL, GS, RA4, the original Krupp, and more), each describes a different shaped bullet - G1 being the current 'standard' comparison shape. Oddly, the G1 bullet shape bears little resemblance to today's more advanced VLD boat-tail rounds and so ammo manufacturers are forced to convert their ballistic data from the bullets native model to the G1 drag model.

They do this because the equation for the G1 drag model results in a higher Ballistic Coefficient value... this does not mean that one drag model is necessarily better than another, what can said is that using a bullets native ballistic coefficient (meaning, if a bullet is shaped like a G5, use a G5 BC - if it's shaped like a G7, use a G7) will always render a more accurate result.

Here is a quick example: A bullet manufacturer has published a G1 BC of 0.659 for their 7 mm Match Target VLD bullet. The same bullet has a G7 BC of 0.337. For the untrained person, the G1 "looks" to be a better number because of its higher numerical value and it's because of this that manufacturers often choose to publish G1 coefficients. The irony here is that using the proper G7 B.C. will result in a more accurate result for the long-range shooter.

The majority of people will continue to use the standard G1 drag model, but there are some bullets in our database, as well as additional factory ammo available, that use a G7 B.C.

For more reading on the topic, check out Fr. Frog's Short Course in External Ballistics.