Ballistic FTE Accuracy

[dannywayoflife]

Just wondered how accurate people find ballistic fte? Yesterday I was testing my 308 loads @800 on stickledown. Muzzle velocity averaged 2298 fps, ballistic stated that I would need 8.7mils of elevation to get me there but actually I needed 10.2. I'm wondering if the 0degree temperature may have had something to do with it as the air will have been denser?

[247sniper]

Just wondered how accurate people find ballistic fte? Yesterday I was testing my 308 loads @800 on stickledown. Muzzle velocity averaged 2298 fps, ballistic stated that I would need 8.7mils of elevation to get me there but actually I needed 10.2. I'm wondering if the 0degree temperature may have had something to do with it as the air will have been denser?

 

 

If you put wrong data in you will get wrong data out. The ballistic programs should only be used as a guide anyway, there is so much more that can play a part in where the bullet goes, if your not controlling recoil correctly and consistently this will have an effect on your bullet trajectory. (Example)

 

Nothing beats real life testing.

 

You state your load is traveling at 2298ftps, is this a typo?

 

 

Steve

[gbal]

+1 on Steve's caveats.

 

Very ball park (as it varies ):

 

A reduction of 1 degree Centigrade reduces mv by 3 fps.

 

 

 

gbal

[dannywayoflife]

No typo thats 2298 fps with 208 Amax from 16" barrel. The MV was measured by magnetto speed on the string of shots in question. I've used the app very successfully before and I know the info which I have in out to be correct.

 

Temperature effects different powders to greater and lesser extents but looking back when I last chronoed the same charge weight at 14 degrees it was about 10fps faster so your 1 degree 3 fps doesn't seem to hold true in this case.

[tackb]

are you using the litz data ?

 

I've just run the numbers on my I phone and come up with 10.37 mRad for 800m ?

 

I'd say check and double check your data input and parameters , or even get someone else to check it for you because we often don't see something obvious to someone else?

[dannywayoflife]

Yes using g7 BC mate. Like I say it's really unusual! Last time I used it in November for 900 yds it was within .1mil now it's miles out! I'll double check all the setting but I've not played with them, I'm wondering if someone else has played with it....

[20series]

The cold air will make a big difference, it depends on what you setting are as you say.

Alan

[Will0]

With BAllistic advanced edition (AE) you can download weather data from the nearest station, it helps to make sure you have your zero weather saved, then on the firing point pull the current data. It will then adjust MV to suit. I was very sceptical, but from summer zero to sub zero winter, it was within 5fps of prediction, well worth the £6 or so it cost

 

Edit: for more precision I could use the kestrel data and input manually

[dannywayoflife]

Just looked mine is the AE. How do I turn on the local weather?

[Will0]

Trajectory - atmospheric conditions

 

Open zero atmosphere, enable atmosphere, there is a balloon blob in the top right corner, that retrieves data

 

Current atmosphere- same as above

[Deserttech Europe]

Hi Danny,

 

My calculations based on a standard day (15'c 1015mbar) show an elevation of 8.8mil at 800 yards

 

if I enter theory conditions of (0'c 998mbar and reduce speed by 30 fps) the result is : 9.2 mil a significant difference but nothing compared to what you are seeing.

 

I would check in the software my zero range BC and velocity first before worrying about much else. I these are looking ok then I would check my zero.

 

Stickledown is notorious for having vertical wind effects but not to the degree you are seeing.

 

Ewen

[dannywayoflife]

Thanks ewen I will double and triple check these.

 

I am speed testing the 243 on Monday at the tunnel range. I'm seriously wondering how fast 49.4 grains is pushing the dtacs

[Shuggy]

If you are absolutely sure of your input data and still getting errors, then you can use the 'truing feature'. This essentially allows you to tweak the velocity until it matches the trajectory that you are actually seeing. I have used this feature before to SWAG a set of data for some GGG ball when I didn't know either the BC for the actual bullet, or an accurate velocity. It worked well!

[dannywayoflife]

Yes I see what you mean but the velocity was established at the time of firing over the magnetto speed. Truing the velocity using that feature would no doubt have given a vastly different velocity

[Shuggy]

These programs are now so accurate, that there is almost always a reason for any errors. I would do exactly what you have said: thoroughly check your input data and look for any 'funnies' such as a vertical wind component. I would only use the truing feature once you have tried everything else.

[brown dog]

These programs are now so accurate, that there is almost always a reason for any errors. I would do exactly what you have said: thoroughly check your input data and look for any 'funnies' such as a vertical wind component. I would only use the truing feature once you have tried everything else.

 

Genau. Vertical wind component.

 

If you hear hoofbeats, think 'horses' not 'zebras'.

[v-max]

Hi I might ask for help regards this as I work ballistic AE in my iPhone. I use to work sterlok & shooter with good results but am lost a bit with Ballistic AE. I tried Will0 trajectory bit but my ballon icon comes up error go to general in settings & location etc. I can't find location in general settings or ballistic settings etc. I work a 6.5x47 now & in put temp etc manually but find my 123 A-Max loads always need tweaked. I must have data wrong some where as I have had to boost velocity to 3190fps out a 24" barrel to get my drop working to my MOA out to 400yrd etc.

[gbal]

Genau und stimmt?

 

We have two examples on this thread (and others elsewhere) of ballistics engine 'oddities'- not for me "errors in the program"(though some basic ones might have 'omissions of minor variables')

 

One is an 'error' of 1.5 mils,reduced to .5,with only an approximate-probably low-adjustment made for temperature,so probably a factor,as originally wondered(maybe 'the' factor.

 

Second is velocity tweaked to a recognised unfeasible '3190' (which would be about 200 fps more than saami safe,so suggests some considerable other input data error.)

 

I do hope these tweaked velocities are not being morphed into "must be ok",because they make it all fit,and become real fps in subsequent loads.

 

So we have probable simple recognised input inaccuracies,easily fixed-like temperature,and some rather less obvious (vertical wind-that won't be measurable,even seen,,but can be there) with ad hoc jigging of velocity to get a fit (heck,why not bullet weight-well that would be 'obviously' wrong-but if velocity is accurately known,it's just as 'wrong'' to distort that. Answers must lie elsewhere,sometimes,as is being recognised.The programs can be very useful indeed.But 'error' in,'error' out'.Jawohl.

 

Maybe the program disclaimer should add :

"For the guidance of the wise,and the faith of the naive." :-)

 

gbal

[v-max]

Hi thanks gbal kind off got your drift on your replie. As said I had sterlok & shooter on another phone but moved to iPhone a couple years ago & got ballistic AE. I used to get on good with my 22.250 out to 500m other than wind but with my 6.5x47 I just seem to be struggling at times I do have a chrony but at my brothers & he is away so when he is home will try get a go with it. My problem now is ground etc as I have just been made redundant as a keeper but could get access to spots. I used to work off the 123g A-Max load with a speed of 2980fps put in which worked for me but now find its out I got the ballon symbol working on app now for current atmosphere etc so will need to re do it all & check. I find the 3125fps speed works more accurate for me other than just .5 moa out etc at 400yrd I have deleted the 3190fps. I actually work in meters but a range was set up in yards on a part of the estate & at my house I got out to 400 yard safely etc. it was 375 meters or there abouts & 6 moa was bang on yet app now saying 5.4moa so not to bad really. I might try get my old phone with other apps going but would really like to just work off my iPhone bae app. My load is 41.4g H4350 with cci 450 in. 24" true flite barrel I recon it be 2800-2900fps area really may be slightly more etc.

Cheers

[gbal]

Hi vmax,some drift is almost inevitable!Sorry to hear your loss,but good to still have some shooting,meanwhile.The 6.5 x47 should of course comfortable outperform the 22/250 as distance increases.

I wasn't criticising anyone-this can all be a bit complex,and ballistic programs are a great help.I know you are not doing this,but eg 375m is about 400y,but its actually 410 y,and that ten more matters to the program - a 6.5 47 (200 zero) would drop 20 inches at 400,and 41 at 500,so the extra ten yards would be a drop of a bit less than 10% of the 21 inch difference,( a bit less than 10% since drop gets faster with distance),lets say about 1.3 inches....which is .3 moa,not much but that's just what a minor distance input inaccuracy would give.Some official ranges aren't that accurate,either

Your load at 2800-2900 seems fine,obviously getting an accurate true velocity would take a major variable out of the calculations,always a good start.Drift.....

.... How is Aboyne-reminds me of measuring issues from the Highland Games days-getting the jump measure from just the right slight undulation on the grass might mean a new record or not-at Braemar the uprights were so close together it hardly varied.....but a precision trajectory was critical! What fun!!

atb

g

[v-max]

Hi gbal thank you very much for your input with this. I got my old phone out & had info in it for a friend who had the same as me being built but I had a Borden action lucky me. His came first & we used my app's etc it was 2950fps to work in fine out to 400yrd etc. this Ballistic AE is a lot more advance & features than my other apps so a bit lost with it all but getting to grips with it now. I know what your saying with distance I am very aware of 10m yards etc makes a bit difference even more so with range & worse the more it goes out. On a good day at 350m I can hold a 1.1/2" bull so accuracy is good in my eyes any way. Yes gbal this is a very nice part of the world never been to braemar games etc but know of it very well.

Big cheers for your input gbal

[gbal]

That's excellent shooting in anyone's eyes.Within sensible stalking ranges especially-or 400y for that matter, there isn't a big deterioration in drop with say 100 less fps-an inch?-especially if a 200 zero- the advantage of velocity is there,sometimes exagerated,though it can add useful energy. It's one of the things the ballistics programs do-allow you to check these details out.The 6.5x47 is no slouch,and not a serious barrel burner,but lots of deer up your way were shot with 6.5x54 M/S cartridges,maybe a heavier bullet but definitely less velocity. 270 of course rather goes the other way! Most work pretty well with a bullet within 1.5 inches of the middle of the heart!

g