Comparing advertised B.C. w/Independent Measurements

[TheNatureBoy]

Some of you may be aware of this report already but its a good read. This was a independent study performed by the U.S. Air Force Academy that "addresses the question of ballistic coefficient accuracy. This project compares ballistic coefficients advertised by four well known bullet companies (Hornady, Nosler, Sierra, and Barnes) with those measured by an independent source (Bryan Litz). B.C.s were determined using calculations at the JBM Ballistics web site. Many published ballistic coefficients are significantly different from independent measurements."
See the report here:
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA554683

 

[jepp2]

Good information, I hadn't see the report. Most BC's were found to be within 5% of the published values. I know Sierra lists multiple BC's for each bullet based on velocity. I wonder how they selected the BC to use for their comparison?

Bullet Name FMJBT
Diameter inches .224
Weight grains 55
Sectional Density .157
Ballistic Coefficients
.272 @ 3000 fps and above
.245 between 3000 and 2400 fps
.235 @ 2400 fps and below

 

[TheNatureBoy]

Not at all surprised that bullet makers would fudge the numbers a bit because its all about selling product. I don't think its necessary because most hunters don't reload and don't care, and target shooters/reloaders will select the bullet with the highest b.c. value anyway.

 

[wncchester]

Calculating BCs from form factors is pointless; just shoot the things, get muzzle velocity and downrange velocity, then work from that.

 

[30Cal]

I think it's laughable that BC's are published to 3 digits.