Ballistic calculators

[PaulC]

Hi i am fairly new to long range shooting and have used the lapua app and strelock app to work out calcs on my .308 @ 1000 yards they are both saying between 28 and 30 moa my load is a 155 scenar .508 g1 @ 2975 fps my actual elevation was 33.5 moa any tips on ballistic calculators or why mine was so far out would be great

thank's Paul

[Jagged 77]

Hi Paul, the results you get out of a ballistic calculator are only as good as the information you enter. There as several factors to consider with the results you found when shooting at extended range - these are just some to consider: 1)How accurate is your 'known' velocity 2) what environmental conditions did you enter (barometric pressure and temperature will be used by the program to calculate density altitude which has a large effect on bullet flight) 3) have you 'trued' your scope?

 

The ONLY thing that matters is the results with your setup on target. You need to record and log all the necessary information and use it to create dope for your set-up.

 

On many calculators there is a facility to match your actual MOA with distance therefore truing your velocity. If you enter all the other information correctly you should see a ballistic curve that matches your actual drop.

 

I mention scope truing purely as something to consider - unless shooting ELR it is not really necessary. You should consider it because not all scopes will dial exactly an MOA - they can be very slightly off which will have a cumulative effect the further out you go. By truing a scope you are accurately measuring a set distance of travel (against graph paper) at an exact 100 yards distance. The point is your scope is not exactly calibrated - there is error inherently present although it may be only very small.

 

There is so much too this, I'd suggest you read through some of the threads both on here and other resources like Snipers Hide and learn as much as you can.

[gbal]

Hi Paul, +1 to Jagged's comments-fall of shot is decisive,and BCs etc can vary a bit between 'quoted' figures and reality ....etc.Not everyone is 'spot on' first time at 1000y,without sighters.

Your actual come up is in the ball park for 308s with a match/target load/bullet at 1000y (with 100y zero),around 32+/- 1 moa,which is reassuring.Its always helpful to see what the going rate others get is on drop etc,and expect yours to be similar(assuming broadly similar rifle/load etc)-that's reality in UK conditions.

Gbal

[Laurie]

Paul,

 

G1 BCs are fine to 500/600, but become increasingly inaccurate at longer ranges. This is because the G1 form is very velocity sensitive, so may be spot on at the muzzle at say 3,000 fps, but way too optimistic after 600 yards at 2,000 fps.

 

The G7 form is much better for long-range use with a typical match bullet like the 155gn Scenar. That's because all ballistic models compare the drag of the actual bullet against that of a 'reference shape projectile'. The G1 is a blunt round nose reference design, the G7 derives from artillery shells that are quite close in shape ('form' as ballisticians call it) to a typical modern HPBT Match bullet.

 

Bryan Litz gives this Scenar a G7 BC of 0.236 which is near top of the class for 155gn thirties. Run a G7 program at your 2,975 fps MV and in 'standard ballistics conditions' (59-deg F, zero % humidity - Ha! Ha! for any UK range - and 29.92 inches mercury atmospheric pressure) it calculates 30.3-MOA come-up needed on a 100 yard zero.

 

The extra near 3 MOA that you actually needed can be due to any or all off the reasons Jagged and GBal have given. If you were shooting recently on a cold day on a low lying range with high pressure conditions on the day, going down to 40-deg (4-deg C) , running at a typical UK 75% winter humidity and 30.5" Hg pressure increases the come-up needed to 31.5-MOA.

 

The other and very likely possible reason for such discrepancies is as Jagged mentions, scope adjuster accuracy. The Gun Pimp on this forum, has done many, many scope reviews for shooting magazines which include adjuster calibration and accuracy, and while the most modern target scopes have improved a great deal (hardly any error on the 8-32 Sightron Series III) in recent years, most makes still have a variation ~ the 5% mark between actual and 'dialled'. Not so long ago, he'd find expensive scopes whose adjusters were up to 10% 'out'. 5% puts you a minute and half out at this distance.

 

The important thing is again as already said - keep a record of your scope settings against rifle, load combination, and conditions. Don't be surprised to find it may be a minute, minute and a half 'out' at the same distance on a different range and/or different conditions. My 155.5gn Berger at 3,050 fps MV F/TR load needs around an extra 'minute' on low lying Bisley (higher atmospheric pressure) than Blair Atholl or Diggle and that can rise to nearly two minutes between summer Diggle/Blair and winter Bisley.

[PaulC]

Thank's for all the info it's much appreciated I will look for a program with ballistic curve feature anmaybe a cure on the net similar too mine thank's again Paul

[PaulC]

Thank's for all the info it's much appreciated I will look for a program with ballistic curve feature and maybe a curve on the net similar too mine thanks again Paul

[CZ Varminter]

Look at shooter. Very good. I shoot my 22-250 out to 600 and 700. Using this. You can manipulate the BC etc. There is always the question as to which to change BC or Velocity but I do BC. Its a little long to type how to do itnof my phone will post sometime.

 

Again though the age old out that which promotes growth and vigour in get that which promotes growth and vigour out!!!

 

CZV

[onehole]

All the above ,,,yep,,,,and zero spot on at 200yds in calm conditions.If you were zerod at 100 then 3 or 4 moa out at 1000 would have been highly likely,,,,Onehole