Thread: Drop Chart and Ballistic Solver Sign Conventions

I've been trying to get my head round this and think I've got it.

So first off with both point of impact (POI) and scope adjustment:
Up and Right are +
Down and Left are -

When you look at a drop chart it shows the POI with no adjustment.
e.g. -9moa @ 500m, -1.5moa @ 90° wind.

When using a ballistic solver the solution should be an adjustment.
e.g. 9moa @ 500m, 1.5moa @ 90° wind.

What's doing my head in is everyone seems to do it different. I have seen:
- inches as POI, moa as adjustment, and wind as adjustment (Shooters Calculator).
- drop as POI, wind as adjustment (JBM Ballistics).
- Results as adjustment (Hornady).
- Results as POI (Berger).

WHY???? like your old Mum would have said when you being problimatic about flavour of ice cream...just pick one.....
learn it and use it..they should all give similar outcome,just learn ONE and stick with it...now for me its easy pointblank online everytime...cause its free and Ive played with it for years....AND ...and its vital for me...I get two lots of info...a bunch of numbers like we used to get on box or Norma ammunition years back...and a pretty picture that makes it dead easy to see what the heck is going to happen at any given range by looking at the curve and looking at whatever range your target is at...
the simple system is easiest...IF I was going to twiddle n fiddle I would tape one of them to stock and leave it there,as many others do.... stuf fhaving to play with phone to work out the dope when animal is found....
find one,learn it and stick with it...
and Im a bush hobbit who refuses to twiddle n fiddle and doesnt shoot past 350.....

For under 250m MPBR is the ducks nuts.
But when you’re out at long range and added spin drift in the wrong direction it’s a miss.

As for why. I started with Shooter’s Calculator, moved to JBM for metric, then found 4DOF had fancy drag models. What I ended up with was confused.

I figured I was better off trying to understand my way out of the hole than shoot my way out.

fair enough......find the one you like best and stick with it would be my advice,agree it would be ideal if they simplified these things and all used the same terms..... hell that goes for most sytems we deal with....

MPBR works for slightly further than 250m/y too heck the rule of three has been around since Adam was a cowboy and it still has lots of merit....its funny looking at the chart now just how similar the main players/cartridges are in trajectory..... to be sure with modern slippery jobbies things will be a bit flatter...but not out of ball park difference really.

out really long is not my kettle of fish..hats off to those who have taken the time to learn it and can do it well....I havent found the need for it yet and cant see me finding it LOL.

Fark im confused as to what you want to solve

If you know your zero is x, anything past that is of course needing to dial up end of, forget the -
If you know what way the wind is going a + or - means sweet f all. Just dial into the wind what ever the value is.
Its either all in MOA or all in MIL, unless you have a kooky scope with dial of one and reticule of other

If you are going to use one of those fancy doohicky phone apps just use the one don't chop and change.
I just watched Norways latest video on wind it reinforces the simple things we seem to overcomplicate using apps and the importance and speed of a notebook or printout.

Originally Posted by Gibo

Fark im confused as to what you want to solve

If you know your zero is x, anything past that is of course needing to dial up end of, forget the -
If you know what way the wind is going a + or - means sweet f all. Just dial into the wind what ever the value is.
Its either all in MOA or all in MIL, unless you have a kooky scope with dial of one and reticule of other

Second this, i’m confused about what needs solving

Originally Posted by Gibo

Just dial into the wind what ever the value is.

Into the wind and up worked great until I had to deal with spin drift and aerodynamic jump. The later being an animal to deal with. It has a head wind component and side wind component which need to be combined with sines and then added or subtracted so keeping track of signs is important.

How bloody far are you shooting? My suggestion, choose a phone app such as shooter or Strelok and all will be done for you mate

Originally Posted by Gibo

How bloody far are you shooting?

It doesn’t take too much. Let’s say your rifle shoots 0.3mil (~1moa) groups and you’re trying to hit a 15cm diameter target at 500m which happens to be 0.3mil. From a 90° 10km/h wind you could have 0.1mil of jump. So you’re out by 50mm or 33%.

Originally Posted by Magnetite

It doesn’t take too much. Let’s say your rifle shoots 0.3mil (~1moa) groups and you’re trying to hit a 15cm diameter target at 500m which happens to be 0.3mil. From a 90° 10km/h wind you could have 0.1mil of jump. So you’re out by 50mm or 33%.

I guess this is why shooting can be considered a bit of an art.
At some distances, and in some wind conditions, you can account for everything, yet environmental variances can be enough that you miss even if you do everything right.
If the potential variances get too large that your hit probability is unreasonably low or unethical, then you need a bigger gun, a calmer day, or a shorter distance, better projectile etc etc.

lets see if I have this correct......your talking a difference of 50mm--2 inches at 500 yards????

@Magnetite, there aren't really any industry wide conventions or standards.

Scopes don't all dial the same. Several euro scopes dial the opposite way than some of the US ones.

Ballistic solvers are also configurable - you can set the application up to show you a variety of outputs.

What I have found works for me is to use a ballistic app that allows you to set the appropriate correction/adjustment matches to the units your scope works in (moa or mil). Some of my scopes are moa, some of them are mil. I just set the app up so I know it will give the the correction in the correct units.

You have well and truely over complicated this and I fear spindrift and head winds have fallen blame to a bad shot? Bad shots happen iv shot animals over 1000 regularly out to 800 not once have I needed more than my dope

I don’t shoot animals at that distance. What size target would you consider a deer at 1000m and what would you consider an acceptable error in your dope?