Nomercy448

DA is Density Altitude. In a nutshell, it’s a singular compilation of Altitude, Barometric Pressure, Humidity, and Temperature - effectively a one stop shop for “environmental conditions” which inputs one number to correspond to a relevant air density.

In other words, it’s a way of saying what altitude the atmosphere currently “acting like”. So I might be shooting at 1300ft physical elevation at my home range, but if it’s cool and damp in the morning, the air will be thicker than normal, so it’s “acting like” I’m at 700ft instead of 1300. Alternatively, on a hot and dry afternoon, the air might be super thin, and “acting like” 4500ft, even though I’m still only physically at 1300ft elevation. So we put in ONE number into our ballistic calculators.

Negative DA’s are largely an imaginary construct - there ARE dry land locations around the world which literally sit below sea level, but not many, and really not many very far below Sea Level in the US. But it isn’t so uncommon for cold, damp mornings even here at 1300ft to yield -500ft DA a few times per year.

With that bullet, you’ll also be more accurate in calculating downrange trajectory if you adopt the G7 model, opposed to that G1 BC. That’s more likely to be the discrepancy than the DA miss. But like I mention, any of these three calculators will have you within 1-2clicks if your inputs are all good.