Ballistic coefficient of cast bullets

[Bull Shoals]

Hope ya'll can help me. I am looking for a chart or listing of the ballistic coefficients of different cast bullets. Lyman Cast Bullet Handbook is very skimpy on this data. I am using a ballistic program and trying to build a library of data. Bullets I am using are a combo of Lyman, Lee and NEI, in .30, .358, .44, .452 and .459.

I tried a search for the board but nothing turned up.

[Junior1942]

The BCs of Lee's are listed in their catalog and probably on their web site too.

[leftiye]

Used to be that boolits had really poor B.C.'s (like in the 1s maybe). Lately I've been noticing that mold makers have been listing quite a bit better B.C.'s. I suspect that, like everything else nowadays, the people doing the talking are fudging a bit. Back a while before people had access to chronographs, the .357 mag showed quite respectable velocities in the manufacturer's fact sheets. As soon as chronographs became affordable, the published data subsided noticeably. Most of them guys don't even shoot across two chronographs, and calculate the B.C. from the data.

[Bass Ackward]

BC decreases the faster you drive a bullet. Or another way of saying this is that it is constantly improving from the minute you launch it. So the location on the measurement can make better or worse numbers.

[felix]

In fact, a very good way, and perhaps the very best way, to "calculate" optimum twist requirements for any projectile is to use the MEASURED BC for it at the maximum range intended. For example, a 0.270 BC in use for a 3200 fps condom would indicate a 14 twist. This technique would eliminate knowing the weight and shape of the projectile. ... felix

[Nueces]

The Lyman Cast Bullet Handbook has BC tables in the back, with a dissertation on CB ballistics.

Mark

[Scrounger]

And how relevant is this for loads/bullets which in general have an effective range of less than 200 yards?

[Larry Gibson]

There are many different "G" forms used to calculate ballistic coefficients. The most common one is the "G1" form and it is the accepted standard for most sporting bullets including cast bullets. However it is not the best for low base boat tailed bullets, VLD bullets or flat base bullets with very sharp noses. Also rimfire bullets have thier own "RA-4" form. Exposed lead nosed RN bullets and HP bullets (pistol type) have thier own form. The military uses the G7 form which is also used for VLD type bullets. When in doubt use the G1 Form as it is the most common. To compare the BC computed with one form against a BC computed with another form is meaningless.

Also many bullets have higher BCs at higher velocities. Depends on the shape of the bullet. However, most RN and FN bullets (most cast bullet designs) will have lower BCs at higher velocity. Some of the more pointy ones may be different(?). I shall find out the answer to that question as I continue testing with the M43 PBL which measures the actual BC of the bullets fired.

Larry Gibson

[John Boy]

Bullets I am using are a combo of ...
Just use the calculator here ... http://www.handloads.com/calc/index.html for the bullets you are using

[Larry Gibson]

John Boy

That calculator isn't that accurate with cast bullets. For example the recent test with 311291 revealed an actual BC at in the 1800 fps range of .230. When the info on that bullet was plugged into the calculator it came back as .266. Perhaps not a great difference but enough to cause inaccuracies in the ballistics drop calculations. This is especially true the longer the range you use but within 200 yards (most used) it is pretty close. You'll only be a couple inches off with drop and wind.

Larry Gibson

[Ricochet]

Those Lee numbers need looking at. Some of their .45 pistol bullets have BCs that look out of line to me just by comparing numbers between their bullets of different weights and nose shapes. However, I don't do a lot of 200 yard target shooting with my Government Model.