Originally Posted by ericpetritz
Does anyone have the Shooter ballistic software for Android? I am thinking about purchasing it but I would like to know what it calculates for this same set of conditions before buying it.
I consulted with the developer on the Shooter application. The solver is a point mass model and it calculates trajectories that match JBM and my programs. In my opinion it's the best program out there for a portable device, but maybe I'm biased
I ran some cases for comparison.
Using single G7 BC of 0.19 and 3250', 10 degrees, 26.22"HgA, and 50% RH
Shooter calculates an air density of 0.07397 lb/ft^3, and a drop of 428.2"
JBM calculates an air density of 0.07397 lb/ft^3, and a drop of 427.9"
My PM Solver calculates an air density of 0.07397 lb/ft^3, and a drop of 428.06"
So all 3 arrive at the same air density from those atmospherics, and predicted drop is within 0.3" at 1000 yards for a subsonic .22 cal bullet.
Using single G7 BC of 0.19 and density altitude of 1140'
Shooter calculates an air density of 0.07395 lb/ft^3, and a drop of 428.0"
JBM calculates an air density of 0.07396 lb/ft^3, and a drop of 428.2"
My PM Solver doesn't accept density altitude input.
A couple notes.
1) In reality, this projectile would probably de-stabilize around 800 yards where it goes transonic, so none of these trajectories are likely to be valid in the real world. However, it is a valid way to compare ballistics programs and their outputs.
2) Because we're going thru transonic speeds for this trajectory, there are some interesting things to consider dealing with the use of density altitude (DA).
DA is commonly thought of as a single metric that encompasses everything a ballistics program needs to know about atmosphere. It's one input that saves you from inputing temp, pressure and hum. If used properly, it can produce accurate results.
However, there is a 'gotcha' if you're dealing with trajectories that approach transonic speed.
The speed of sound in air determines the Mach number of the bullet, and the speed of sound depends on air temperature. If you're giving a program only DA and no information about air temperature, the program can't know what the speed of sound is, so it assumes 'standard' value. However, if the actual air temperature is much different from the standard value, the program will be using a speed of sound, and a Mach number that are incorrect which leads to inaccurate trajectory prediction.
In order to be fully correct, a program that accepts DA as an input still needs to know air temp in order to make the speed of sound calculation and get the right Mach number. If you're using DA and not input temp as well, your solution will have error in cases where the air temperature is not 59 degrees F.
Having said all that, the error only becomes significant when the trajectory gets down to transonic speed.
This was probably way more than you wanted to know!