Ok, I'm playing around with the Shooter's app on my new Droid X, and I have to input the Drag model for each load I'm adding to the program.   How do I find out what model each bullet is?   G1 through G7?  Is there a listing somewhere?    Thanks for the help.

Is there a menu/option for choosing the bullet?  Bulletflight and Ballistic have a database of bullets which typically lists the G1 model and puts all the bullet information into the load.

There is a bullet library, and when I choose the bullet, it usually asks for G1 or G7; just the two.    I noticed that in other programs, there are G1 through G7 models.    I've inputed the coefficient, and left the model at G1 so far, but I'm not sure if I'm messing up data by doing that; not knowing the real model number.  

If I know the coefficient and the length, and weight, shouldn't the program use those, and ignore the model number?   I was hoping the model number would be listed on the bullet manufacture's website, but alas, it isn't.   At least, not Sierra's.

The coefficient is the ratio of measured data to one of the 'standard shapes' also based on measured data.

If you have  BC of 0.5, that is the ration to one of the standard shapes/models to the bullet you have.

The G7 B.C. number will be a lot smaller than the G1's (or G3&G5s, I think they are?) B.C.s that the bullet manufacturers usually use, so if a you're doing a 175 Sierra MK and have a .492 BC number, you can be assured that it's a G1 model, not a G7, which might be .311, or something like that.

If your program has preloaded BC's, like the QuickLoad program, it should say what model it needs to use, or is using, or there will be a pop-up menu that let's you select what model.

Go to each bullet maker's site and write them down, or input them.

I just put 70 bullets into a PDA program that uses the G1 model, which most online freeware uses (I also use www.ModernBallistics.com), which is G1, as well and both give similar numbers.

I had to go to my reloading manuals and online sites for the B.C.s, as this program isn't preloaded with any data.

As an example, Brian Litz, Berger bullet's head ballistician wrote a book where he tested a lot of bullets, both Berger's and others.  As an example, he tested Hornady's famous 7mm 162gr AMAX, with a claimed BC of .625 (G1 obviously).  Litz found it to be .599 (G1) in reality and it's G7 B.C. is .399.  

Bullets made to the G7's physical profile (modern artillery shells) will differ from G1 profiles (spitzer, flat base WWI profile) in that their true B.C. will remain MORE constant (90%-95%) over the typical velocity range, than G1 modeled bullets.

If you were to look at Sierra's mauals for B.C. (G1) they give you three numbers for B.C..  The first might be 'above 2800 fps', the second might be '2100-2800 fps' and finally, the last would be '2100 fps and below'.   This is a better way to list it, but what number do you put in?  Do you average the three?  

I usually just pick the 'sweet spot' and figure B.C. out for real, on the range.

Recapping:

Higher numbers on the manufacture sites will be G1, unless specified in a separate column, like on Berger's site.

If your program doesn't preload the bullet data, or give you a popup menu for G7 vs. G1, I'd assume it's G1.  

G1 vs. G7, will be a higher number, if you have two numbers in front of you for the same bullet.

G7 is a more consistent number, because that number is static across MORE of the velocity band, than the G1 number is.

B.C. is just a number, much like reloading book data is just a guide to go by.  It's not an 'absolute'.  You ultimately determine what the TRUE B.C. is, by getting out and clocking your rounds and finding out the drops at any given distance.

Chris

Wow thanks for the response!   The program does allow for different Coeff for different velocitiy minumums.    I still feel lost as to what G number to put next to the bullets.    

Am I right to guess that boat tail designs, such as the Sierra Matchking will be a G7, as apposed to the Spitzer flat base design, being a G1 for say a 150gr?

What a bout something like a 36gr .223 .22lr bullet?   I found the BC of .126...?

Unless you have a G7 B.C. AND your program gives you the option of running that G7 B.C. in its program, sellect G1.  You won't get your correct drop table if you use a G1 B.C. number in the program under a G7 option.

Keep it simple and most of the data you will find on a particular bullet's B.C. is still the G1 number, so you'll want to use that.

If you go to Berger's site, where they list G7 and G1s (IIRC), you can use that G7 B.C. and tell your program that you'll want the more accurate G7 dope.  You can also just plug in the G1, run your program for G1 and compare and contrast the differences.

Most all B.C. numbers you'll find on the net, are G1 numbers, so just tell your program to use the G1algorithm and confirm out on the range, as that data might be off slightly, vis-a-vis your real world results.

Chris