Ballistic co efficients

[adam]

Hi all. I'm expecting my new rifle any day now and I'm sorting my loading gear out and getting things ready. I'm using Sierra infinity 5 to print my drop charts. However I have read in numerous articles that the ballistic co efficients of bullets are never as close to what the manufacturers state.
I'm going to be re loading for 39 grain sierra blitz kings and hornady 40 grain v max and also 32 grain v max. I was wondering if any one has accurate ballistic co efficients for these 3 bullets? Or what do you guys do to print accurate charts for long range shooting?
Many thanks in advance
Adam

P.s I will get pics of the new toy on here asap!!!

[Bayou City Boy]

Computer driven ballistic programs give you and idea of what to expect from a certain cartridge/load, but the are "ball park" at best.

If you plan to do a lot of long range shooting, the only sure way to develop ballistic charts is to shoot at the ranges you are interested in and get real live data for your particular rifle and load. Because there are so many variables, including several different approaches to calculating bullet BC, and since bullet BC is a variable versus velocity, real life shooting is the only really good answer.

Besides, if you plan to shoot long range quite a bit, you need to practice long range and then develop drop charts from there that reflect your rifle's performance.

-BCB

[Hotshot]

adam,

BCB is right on with his advice(as usual). Don't worry about nitpickin a couple hundreths on the BC of a bullet. Two similar rifles shooting side by side will have variations more than the slight correction of the BC. Use the chart to get close and practice, practice, practice. Altitude and humidity can vary your performance more than slight BC correction as well.

[adam]

Cheers guy's. It is a bit awkward for me to set up targets at long range unfortunately because of the way the land lies near me. I have to shoot across the tops of two or three fields to get long range shots!!!! But thanks again for the advice I will try it

[Rick in Oregon]

Adam: The advice given is spot-on. Actual range test yield the most accurate results, but I've noticed that if you use the Infinity program, enter all the parameters as BC and other hard data per the manufacturers numbers, enter all the other environmental data such as temp, baro pressure, altitude, etc., your charts will be quite close to actual bullet performance, not exact mind you, but close enough to hit at extended ranges on fox-sized targets such as you have there.

Actual shooting to confirm is always the best, but as noted, not always possible. For this reason, be as precise as you can with all your data entry, and you may be surprised at just how close your POI actually is compared to your carefully made up come-up chart. Getting accurate, precise data entered is the key here.....

[adam]

How much difference can altitude make to the bullets line of flight? Does it really change things that much?

[Rick in Oregon]

YES IT DOES! If I use one of my come-up charts for my "home range", at 3,700' elevation, then go shoot at my favorite ranch at 4,500', all my shots will be high, especially at extended ranges. It makes a HUGE difference, that's why every ballistic software program includes the ability to enter the correct elevation where shooting will take place.

Where I usually elk hunt, the elevation is over 5,000', so if my rifle is sighted in at home, all shots will go high guaranteed.

Elevation/air density plays a critical part in the ballistics equation.

[rayfromtx]

Hey Rick
I see less drop at higher elevations. This isn't what you see?

[Rick in Oregon]

Ray: Yep, right on. I had to go back and edit that post, as my brain said "high", but I typed "low". It is amazing how much error can be caused by elevation if not taken into account.

Thanks for catching my typing blunder.

[Bayou City Boy]

Adam:

The attached link provides a very good explanation of what has been mentioned here.

http://www.exteriorballistics.com/ebexp ... 5th/31.cfm

If you have lots of time and want to read for hours, click on the Exterior Ballistics tab on the Sierra web site and you can get eye fatigue wading through it all. But its all very good information written by some very knowledgeable folks.....

-BCB