Reverse ballistics

Fireman_DJ · Posted: Sat Dec 31, 2011 4:02 am Post subject: Reverse ballistics

I have a strange one for you.

Reverse ballistics, where by I enter specific data like distance and bullet drop for a few ranges and PointBlank will work out the velocity and/or bullet BC.

That data can then be used to compute the NORMAL ballistics.

This removes the need for a person to own a chronograph AND have to shoot at it from 100yd away or trust the manufacuters BC data (if they even supply it).

I thought of this as I'm making changes to my ammo loads soon.
I ran PB with the data I have, but it put me about 6 minutes above the target at 1000yd.
Not saying PB failed, just the data I was able to obtain and input wasn't accurate enough.

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3572 Location: Utah

The BC Calculator basically works like this. Knowing muzzle and 100 yard velocities, it adjusts the BC until it finds something that matches the velocity drop off.

Something similar could be done knowing drop, but you would need at least two points of height at known distances to compute the final trajectory... and it would only be as accurate as the two initial data points.

-DallanC

Fireman_DJ · Posted: Sat Dec 31, 2011 3:22 pm Post subject: Re: Reverse ballistics

I'm aware of that.
But it's easy to "count the clicks" from what you've shot at a specific range.

I'd say we'd want three points of data.

The rifle/scope data (ie, scope mounting height etc).
The first distance and MOA change from zero.
The second distance and MOA change from zero.

You wouldn't really need to know full bullet drop from the muzzle, just the change between two known distances.

And as I said, no chronograph required, just a season at the range shooting two known distances.