Ballistic programs

[onehole]

Following recent experience in getting my 308 to track well within a ballistic program I was wondering what you guys do and what element do you fudge when inputing data? do you tweak velocity,bc,zero or what to make a program work spot on in decent conditions? It may be that my chrono is telling me porkys but have checked out several programs and all give me whats actually happening in the field when I plus 50 fps on initial velocity.You may all know from previous posts that I favour a very accurate zero at 200 so pretty sure I have a good base but by the time I have gotten out to 450 to 640 I,m up to 1.25 moa out {going high}} if I use chrony reading,,,,,add 50 fps and I,m on track at these extended ranges .I have picked velocity,bc and zero as main culprits to tweak as anyone of them could be suspect and I suppose a combination of all three in small question could well amount to my need to tweak one of them at least,,,,,I just saw velocity as the easiest one to fiddle with????what do e think? Regards Onehole.

 

Thought I would add that shooting conditions are pretty much flat and no real temperature issues,,,,warm summer eveings

[Foxshooter]

What BC source are you using? G1 or G7

 

Manufacturers are always a bit on the optimistic side, Bryan Litz books have some G7 BCs for quite a few bullets calculated from real world data. Its a good place to start fudging figures.

 

Depending on what program you are using you may also be able to 'teach' the program your own real world data so it alters its calculations accordingly. NF Ballistics allows this as I believe do others

 

Mark

[onehole]

What BC source are you using? G1 or G7

 

Manufacturers are always a bit on the optimistic side, Bryan Litz books have some G7 BCs for quite a few bullets calculated from real world data. Its a good place to start fudging figures.

 

Depending on what program you are using you may also be able to 'teach' the program your own real world data so it alters its calculations accordingly. NF Ballistics allows this as I believe do others

 

Mark

Thanks Mark,,,,G1 mostly G7 would help in this scenario but only a little and if the manufacturer is optimistic then a true figure {lower I presume}would not help as even more ups would be seen in the program to compensate?Thanks for your comments and suggestion of teaching the program? I,ve survived on fairly simply inputs and outputs and filed testing for quite a while ,,,in simple terms what do you mean when you say "teaching" the program to alter calculation? I presume this is more than a velocity fib?keep it coming please,,,,,,,,,,,,

[gun nut]

Hi Onehole,

I think your spot on with altering the velocity, it's the weakest link in the info you have. Unless you've got a top end chrono I would imagine most are 2-3% out at least, given real life results with my rifles I know my chrono measures about 3% more than reality.

 

Mike

[bbob]

I find altering speed/FPS of your bullet is the way to go with Ballistic AE but do it in the field . Also like to have a 200yd zero on my .243 & .22BR once your rifle is zeroed put another target board out at desired distance say 300 or 450yds dile in to your scope as per ballistic programme reading and see we're your bullets are hitting then adjust speed accordingly increase or decrees speed on your programme

Personally I would never take the readings of my chronograph as a true reading but it is a good starting point, also like to shoot from a cool/cold barrel if possible so you can be in for a long day

[Akeld]

Are you putting in accuarte temperature, pressure and humidity values as well?

[onehole]

Are you putting in accuarte temperature, pressure and humidity values as well?

Probably not and a very good point.I am aware of the effects of course and in winter would be especially aware but my shooting these days is generally in "fair" weather conditions only but would add a click or two as the temperature drops towards the end of the day.Perhaps I am becoming too much of a generalist rather than a specialist these days.It was just that I had a pretty consistent over dialing problem with my 308 regardless of conditions so something had to be tweaked.Thanks for pulling me up on this anyway.

[bbob]

As Akeld has pointed out it is a must to input all current data into your ballistic program .

[onehole]

As Akeld has pointed out it is a must to input all current data into your ballistic program .

Agreed ,,but my problem was that the program led me to excessive over dialling in pretty much "good conditions" so suspected velocity or bc basically rather than a conditions input.Again we have to have some sort of base "scenario" My base conditions were fair fine weather and generally just a nice day and an honest 1 inch centered group at 200 yards.I felt I needed to correct/fudge something other than condition input.Perhaps there is a case for a 300 yard fair weather zero!!!! dohhh,,,,thanks guys,,,come on keep it coming,,,,,,,,,,

[gbal]

Agreed ,,but my problem was that the program led me to excessive over dialling in pretty much "good conditions" so suspected velocity or bc basically rather than a conditions input.Again we have to have some sort of base "scenario" My base conditions were fair fine weather and generally just a nice day and an honest 1 inch centered group at 200 yards.I felt I needed to correct/fudge something other than condition input.Perhaps there is a case for a 300 yard fair weather zero!!!! dohhh,,,,thanks guys,,,come on keep it coming,,,,,,,,,,

OK-perhaps 'good conditions' is a little vague-programs run on precise input,(or rather will have always some default entry for the raft of variables they have been programmed to use-they may not be comprehensive). While temperature eg is readily measureable,and therfore accurately factored in,how about other variables....a 5% error (what is that in 'change in good conditions?") in air density means a .3 inch elevation change at 300 yards....not huge,but is 5% a huge error...? There are a whole raft of these variables...which can be cumulative. Wind speed too,perhaps the big source of shooter error,has vertical effects,around an inch at 300 for a 2mph error,with quite a modest wind (say 5mph-thats averaged to the target,hence difficult to measure...)

What fun!

Gbal

[onehole]

OK-perhaps 'good conditions' is a little vague-programs run on precise input,(or rather will have always some default entry for the raft of variables they have been programmed to use-they may not be comprehensive). While temperature eg is readily measureable,and therfore accurately factored in,how about other variables....a 5% error (what is that in 'change in good conditions?") in air density means a .3 inch elevation change at 300 yards....not huge,but is 5% a huge error...? There are a whole raft of these variables...which can be cumulative. Wind speed too,perhaps the big source of shooter error,has vertical effects,around an inch at 300 for a 2mph error,with quite a modest wind (say 5mph-thats averaged to the target,hence difficult to measure...)

What fun!

Gbal

mmmmmm !errors and immeasureables all over the place,,,,,,dohhh! what fun ,,yep love it,,,,,,,,,