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Swarovski1

Ballistic calculators

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I use a the shooter bal cal.

I have noticed when I typed in current conditions that the velocity with the 180gr hybrid had dropped from 2884 fps to 2792fps with a muzzle velocity variation entered as 10fps.would you lose 90 odd fps.the bal cal obviously doesn't know what powder I use.

My zero details were 57.2f.baro 30.386.humidity 57.

Current details the other day was 37f.baro 29.766 .humidity 81.

Adjust bal cal to 2 fps and it makes velocity loss more realistic.

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I use a the shooter bal cal.

I have noticed when I typed in current conditions that the velocity with the 180gr hybrid had dropped from 2884 fps to 2792fps with a muzzle velocity variation entered as 10fps.would you lose 90 odd fps.the bal cal obviously doesn't know what powder I use.

My zero details were 57.2f.baro 30.386.humidity 57.

Current details the other day was 37f.baro 29.766 .humidity 81.

Adjust bal cal to 2 fps and it makes velocity loss more realistic.

How do you calculate what 'realistic velocity loss" would be?-especially as you ask ' would you lose 90fps?'-seems you don't know.

 

You do have a 20 f degree temperature drop ( and other differences) which will reduce velocity.

The effect varies with powder burn rate and exact temperature range,though ball park 50 fps here might have been "expected" for temperature drop. Look it up!

 

Adding in an false data (2fps MV sd) isn't the way to get reliable output wrt your load.Errors seldom cancel out neatly-and is there another error anyhow?

 

Holes on target tell the truth-did the rifle shoot low commensurate with the calculated velocity drop using accurate data input?

 

gbal

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Hi George.next time I test any ammo I will chrony these loads again.I've chronied them when I did load developement.i think it was last autumn/winter I was testing a 168gr amax in my 308 and noticed a 50 fps drop and Laurie said that n150 is one of the less temp sensative powders.i would be intrested to see what others have found out in real time.as both my rifles are zeroed for hunting abd i use them for target aswell i know that switching from mod to brake there is 1.5 moa ish difference in elevation depending on what brake i use.using my bal cal i would put my first shot most times at 1000yds.windage being the fussier one as fig11 is 17 inches wide.na prob on elevation.there is a poi difference between different bullets only being slight.enough at times to put me of the edge of fig11 at times.do I trust my bal cal totally...?

No would be my answer. Swaro

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Hi George.next time I test any ammo I will chrony these loads again.I've chronied them when I did load developement.i think it was last autumn/winter I was testing a 168gr amax in my 308 and noticed a 50 fps drop and Laurie said that n150 is one of the less temp sensative powders.i would be intrested to see what others have found out in real time.Swaro

OK-fps loss did seem a tad more than 'expected' though there is variability...and we don't know what parameters/default values are in the ballistic app...or most others...it's not at all uncommon for the system defaults not to be met by the input-scope height being a common one (or 300y drop being measured precisely enough-3 shots inches apart..precision??)

 

I'd not bet my rifle on most chronos if they have not been calibrated recently...magnetos seem pretty reliable and valid,though.

We tend not to get the more extreme conditions of some US ranges here,something perhaps overlooked in following US 'must have' powder choices...I'd expect Vihtavuori to be Euro suitable!

 

You are right-there is no substitute for well collected real shooting data- "Holes in paper", trumps 'gaps in apps' :-)

 

g

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All the ballisticians on ukv and only George replies.

 

F*** rushes in,where (minutes of ) angels fear to thread?

 

:-)

 

G

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All the ballisticians on ukv and only George replies.

 

 

take some time to write a comprehensible post then, if you can't be arsed to explain I can't be arsed to answer

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I use Strelock Pro and there's a useful calibration feature on there using actual bullet drop between measured distances (ie trajectory) for various conditions.

 

 

I simply plugged in what Strelock (calibrated) told me for my MV's today for the 49 degrees F temperature and it gave me 2,487 fps for a 190 SMK in 30 cal compared with 2,501 (measured and calibrated) at 56 degrees, and dialled in the firing solution for 600 yds. It was spot on.

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Thanks for that.14 fps isn't a lot for 6 degree difference.your es could be that much easily.i nearly got to chrony my main loads again.i was probaly a fraction not light enough to do them so I sent the shots at s load developement targetb

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Your temp is the only major factor for muzzle velocity, the rest of you enviromentals will determine how fast it sheds velocity down range. Chrony at two different Temps to determine fps per degree and enter into Calc. I chronograph a minimum of 10 rounds but prefer 20. Always shoot on paper first then true your calculator.two loads for example, My 308 load running imr 4064 has a variation of 0.5 fps per degree. My Creedmoor load running H4350 has a variation of 0.13 fps per degree. AB toolbox app has a tool for estimating velocity difference from chrony to muzzle, astonishing how much velocity some bullets loose in the first few feet.

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308 167g BC.45 MV 2690 100y vel 2497 so loss over 300f is 200 fps,average 2/3 fps per foot

 

CM 125g BC.45 MV 2950 100 vel 2741 so loss over 300f is 200fps, average 2/3 fps per foot

 

GIven velocity loss increases with distance, the velocity loss near the muzzle will be a little less than the 100y average,so velocity loss over the first 6 feet cannot be more that 6x2/3 fps ie 4fps

 

so a screen chrono 6 feet away is probably under reading mv -accurately-by 24f ps from distance alone.

 

Alas,most screen chronos have considerable potential for actual inaccuracy (screen not precisely 12"inches apart(or whatever calibrated as) variable light;not perfectly vertical;moving -variably -bottom to top in wind,bullet at slight angle,very pointed bullet not consistently detected,etc etc....though all this is of the order of a couple of clicks out at long range).

Actual measurement error intrinsic to chrono....well,variable from 2% on up.....the lower values need a top Oehler,or not a sight screen system,and that is with expert set up,not plonked down in a field.

So ten fps discrepancy from realty to reading is not unlikely.....it won't ruin your day,but don't blame the ballistic solver for all the mismatch,but it's an unknown with basic screen chronos.

 

gbal

 

Screen spacing error for 12inch screens : .016" is 4fps; .063" is 16 fps; .125" is 31 fps

 

Average errors in testing 30 and 22 cal 1 to 20+ fps (very low errors are Oehler and some non screen chronos)

 

Chronos with screen spacings less than 24 inches never got below +/- 10 fps error

 

(Litz testing).

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Not sure I grasp all that info Mr litz.your quite a source of information George.mostly good but some not so but good to take in all the same.i do always zero and chrony in the same place with the same chrony.occasionly a zero check elsewhere.i wished I had chronied the weekend now as there was around a 20 degree difference.cheers G

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Ah well....if it''s information that is valid,but inconvenient,check with god. (in this instance,not B Litz!);if it's not clearly expressed ,ask-sometimes short falls short.

eg " chronos are crap' is just chronic crap-and as you imply,they can be ok for comparative data-their errors are relatively reliable and stable! (I mean screen ones)-and not Babe Ruth (out of the ball park).

In the field (of dreams) we would have two Magnetospeeds,and a back up calibrated Oehler. Unlikely then to go "Tits up in a ditch" *

g

 

* Proulx,Annie "Fine just the way it is" p221..."there was no answer to that....the beginning descent into the dark watery mud".

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Fahrenheit. And yes chronographs aren't 100% accurate, that's why we shoot on paper first then go to the computer to verify and true it to real world data.

Montana- "A River (of truth) Runs Through It." Mc Lean

 

g

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Every scale weighs different.every chronograph reads different.powder batch to batch differs as do primers.cases.bullets.reloading tools etc etc etc etc.things will never be perfect who ever makes them.it seems we are rather anal with all these things and theories and seem to get worse at it.new technology brings more unknowns.Gouldy...

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I've eventually got around to re-chronying a few of my loads with the temperature 17 degrees lower than when I first measured them.i only fired one of each.its a ballpark figure I am after.i am not Brian litz.

52.5gr RS60 162gr amax load originally shot 3000 fps. Today it shot 3003 fps.

52gr rs60 180gr hybrid load shot 2890 fps. Today 2900 fps.

My recently accuracy tested 56grs H4831sc load hadnt been chronied until today which was 2740 fps.be ok summer load.the rs60 hybrid load autumn/winter load.

Today I chronied the 180gr scenar l load.accuracy was ok on 51.5grs but showing pressure signs.chronied the 51grs load and they were doing 2888fps.they shoot faster than hybrids on same powder grainage on different different powders I've tried.not really sure what to think on these findings.maybe ukv's own Brian litz better known as gbal explain this phenomenon ?

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One shot is no basis for anything,however:

If indeed your velocites lower in colder conditions then something is clearly wrong-either with the warmer chrono reading(s)-(please don't say that was only one shot also),ot the cold reading,or the laws of physics don't apply in your vicinity. OR of course any/ of these.

 

I am sotty,I have absolutely no idea what the word salad beginning "My recently....winter load" means.

 

I think-? -you then say that two differnt bullets( both 180g?) give sloghtly different velocities (scenars faster than hybrids?-but only one velocity is given).If this 'data' is based on one shot,nothing at all can be said.

IF there is a real velocity difference,then I'd consider the bullets are simply not the same in diameter or bearing surface (essentially,friction between bullet and barrel is not the same.The clearest examples of this are with moly-ed bullets- which are just slippier-within the same maker/weight-like Lapua naked and moly-ed.

 

You are at least right not to know what to make of it,other than much is rather 'tits up in a ditch'.Ref Proulx,A "Tits up in a ditch" from her 2008 collection of short stories "Fine just the way it is." It isn't.

 

gbal

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A 2 or 3 of each were chronied in load developement.cant see the point of anymore.its just a waste of consumables and barrel life.whatever is going on its certainly consistant.as far as I know the RS powders are like hodgdon extreme powders.not temperature sensitive.

Yes George scenars go faster than hybrids on whatever powder I tried.like you said.bullet is a different design.

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OK,my mistake ...it's 'Tit up in a ditch'.

 

Singular.

 

 

But if one shot means consistent,and there is no temperature issue,why were you asking?

 

Glad we have sorted the ''bullets can be different" ...I didn't even waste one... :-)

 

g

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I can't do perfection George.dont want to try.it causes anxiety and frustration.i only need a few readings to get me on the target at 1000yds.if I had 20 readings the info would make very little or know different for my purposes.get on the target and make slight adjustments.

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