Ballistic Calculator accuracy??

[cowtownup]

I've been using Strelok for about a year now with my Stevens Model 200 in 308 Winchester. I handload 175 SMKs over 43.5 grains of IMR-4064 and had roughly estimated based on data from my reloading manual that the muzzle velocity was around 2625 FPS. The ballistic calculator really impressed me with how accurate it was all the way out to 500 yards (which is as far as I've shot so far.) All is good...

Well I had the opportunity to shoot my handloads over a chronograph last weekend and found out that they were actually leaving the muzzle around 2745 FPS. A difference of 120 FPS faster... This difference in velocity equals a difference of 6" of drop on my ballistics calculator (Strelok) at 500 yards. I would have missed had I used the true velocity of the load..

What I've learned is that you have to develop your own dope charts for your own load. Not really depressing to me cause I like to shoot and handload so I will enjoy it. I am interested to hear other folks experience has been with this situation and maybe how you handled it..

 

[jmr40]

I believe the calculators are accurate enough to get you close enough to be on paper at extended ranges. You still have to shoot and see exactly where you're hitting.

 

[The_Next_Generation]

I've never had the chance to chrono my loads, I just assume linear relationships between charge-weight and velocity, then calculate a theoretical MV from that for my particular charge weight.

So far, this method has been extremely effective. I used this technique to make a 1st round hit on a 6" round plate at 600 yards with a 75gr Hornady BTHP out of my 18" AR15

 

[Legionnaire]

Tag. I have a chronograph, but have not really played with ballistic calculators. Need to work up some loads for a couple of new-to-me rifles in .260 Remington. Looking forward to what others contribute here.

 

[SatCong]

I also use Strelok and for a old man shooting long range it's not bad. Been real good for me at 1,000 yards. And out to one mile.

 

[MCMXI]

I had the opportunity to shoot my handloads over a chronograph last weekend and found out that they were actually leaving the muzzle around 2745 FPS. A difference of 120 FPS faster... This difference in velocity equals a difference of 6" of drop on my ballistics calculator (Strelok) at 500 yards.

How do you know that the chronograph is correct? I replaced a Shooting Chrony with a CED M2 which indicated that my match load was moving about 75 fps slower than the Shooting Chrony reported. The CED M2 data matched up much better with results on paper. You can't beat data obtained from shooting at various distances but you might want to try a different chronograph. Also, some ballistic calculator programs have trajectory validation options to fine tune the data. Another issue is that a ballistic calculator is only as good as the data you put in. Regardless, ballistic calculators and chronographs are just tools that can help to solve part of the puzzle such as velocity variation, but nothing beats real world data obtained from shooting. Consider that there's no way to calculate the BC of a bullet. BCs are obtained empirically by shooting over multiple chronographs at different distances or using Doppler systems.

 

[Jim Watson]

Does Strelok use the staggered G1 BC's that Sierra publishes?

 

[SatCong]

Yes, I use Sierra on my set up.

 

[taliv]

it usually takes me a while to figure out what i'm doing wrong... but once i get everything right, the calculators work fantastic.

garbage in, garbage out

 

[cowtownup]

I have input as many variables as I could. I am for certain that I need work on the weather variable some. I've enjoyed using it really, it makes shooting more fun for me...

 

[Ankeny]

I spent several hours Monday shooting a new upper on an AR at 100, 200, 300, 400, etc. out to 900 yards in order to develop a drop chart for a custom turret. After making sure my scope is perpindicular to the universe, I will chronograph my loads. I have a huge piece of cardboard that I'll shoot a couple of groups on at 500 yards using a 200 yard zero to see exactly how much drop I have. I also record the environmental variables for the day such as elevation, barometric pressure, humidity, etc.

I then return home and measure the distance to the center of the scope as close as possible. The velocity, scope above bore, and environmental variables all go into JBM ballistics using the BC from Brian Litz if available. I will tweak the velocity a hair if necessary to get the same correction in MOA at 500 yards to match the actual drop. Then I print the chart.

Back to the range I go to actually shoot groups at 100 yard increments back to 700-800 yards. The real problem is finding a day when there is minimal mirage. As soon as the chart is developed and confirmed a couple of times, the data goes off to Kenton Industries for the turret. Simple but time consuming process.

 

[ArchAngelCD]

Like said above, GIGO...

The formula used in ballistic calculators doesn't give inaccurate information, it's all up to you imputing the variables correctly.

Almost everyone who has spent time on a range shooting knows that no data from paper and books can match shooting your rifle with your chosen ammo to be sure what that combination will do.

It's the same with an SD handgun, especially ones with fixed sights. You have to shoot the gun with your carry ammo so you know where the POI is. Without knowing you don't know how to adjust your POA.

There is no substitute for shooting your gun...

 

[1911 guy]

The ballistic calculators work and as others have said they work as well as the data you feed them. Part of refining that data is your dope book. Making notes of your shooting sessions (wind, temp, altitude, barometer, etc) gives you far more accurate information than just inputting standards and defaults.

Your book is part of your routine for making a long shot, even if aided by a calculator. Dope isn't just a name for a book, it's an acronym: Data On Previous Engagements. D.O.P.E.

Part of the reason that your velocity is different than the published velocity is your barrel. Three identical barrels with shoot the same load at three slightly different velocities and three different points of impact relative to barrel axis. No two barrels are exactly the same.

That's part of the fun of long range shooting, figuring a rifle and load out.

Dang. There's been a few threads lately on long range shooting and it makes me want to dust off the .308.

 

[chaser_2332]

Taliv is right, u have to make sure all parameters are correct on your end before you can expect correct results.