High BC for Speer bullets?

12 February 2002, 16:39

<bearlake>

Has anyone noticed that Speer bullets seem to have a higher ballistic coefficient then what they should have? For instance the .284(7mm) 145gr BT spitz-SP has a BC of 0.502 pretty good right? But most of the "preimium" bullet makers are around .4?? or .3??. How can a soft point spitzer have a higher BC then pretty much all the match bullets in its same weight class ie-130gr to 168gr? I mean the Sierra 168gr match king has a BC of .488 What the Heck??? I have found this to be the same with most Speer spitz bullets between .22 and .30 cal. Are they just shaped that good or what?

12 February 2002, 16:51

ricciardelli

Speer writes the specs, published the manual and the specs...

------------------
http://stevespages.com/page8.htm

12 February 2002, 17:56

<PaulS>

Bearlake,
The Speer bullets have the ballistics to back up their published data. I have tested the 30 caliber 150, 165, and 180 grain bullets by comparing the ballistics table with the actual flight at varying ranges. I do know that they base their BCs on the G1 table while not all the other bullet manufacturers use the same table it can make a big difference on the number that they show on their spec sheets.

when comparing apples be sure to use other apples.

PailS

------------------
stay safe and live long!

13 February 2002, 14:04

Pyrotek

PaulS is right, BC is a comparative number based on a standard, if different maunfacturers used different standard, the data would be defferent.

13 February 2002, 15:15

denton

It would be interesting to know just how much effect this has... don't know. But Hornady bullets are nearly conical on the front end, hence the name "spire point". Speers and some others have a very different profile, and are called "spitzers". I have supposed that this difference in front end geometry explains the difference in BC. According to the numbers, Speer flat bases have almost the same BC as Hornady boat tails. Anyone have definitive information?

13 February 2002, 18:20

<bearlake>

So who is rite? Who is getting these numbers the rite way? Is Speers way of number crunching a real representation or is Sierras more accurate?

13 February 2002, 20:06

<PaulS>

bearlake,
with all the different colors of houses who is painting their house the right color?
It's not a matter of right or wrong just difference. If you ask they will tell you what table to use to calculate ballistics.
The G1 table used to be the standard but with the low drag bullets of today other tables are used.

PaulS

------------------
stay safe and live long!

14 February 2002, 02:15

Hot Core

Hey bearlake, Interesting mix of responses and I believe I agree with all of them.

The apparent difference in B.C. can be very confusing "IF" you focus on it. What really matters is "Point of Imact" as a particular bullet leaves "your" firearm. And, irregardless of what the Ballistic Charts say(good for a guideline only) it always comes down to shooting the Bullet you want to use at the distances you intend to shoot at Game(or Targets) and create your own Drop Chart.

What you have discovered, if taken afield, is that some really sleak B.C.s just don't fly as flat as predicted and some blunt B.C.s seem to fly better than expected. But, the only real way to know for sure is to shoot the bullet and see where it's group impacts.

Some folks like to make a big deal of "Retained Energy" being so much more with high B.C. bullets. On the surface, that looks like it has merit. But the actual Bullet Construction and how it reacts at different Impact Velocities is much more important to me. Some of this can be "estimated", but it still does not replace actual On-Game results, using many of the same bullets with varying Impact Angles. Over time, the reputation for how well specific bullets work becomes evident.

------------------
Good hunting and clean 1-shot kills, Hot Core

14 February 2002, 03:28

<DuaneinND>

Ballistic coefficients change with velocity, many companies pick the velocity that give the highest possible value, Sierra now uses an average of the BC with the velocity from the muzzle to 600 yards, this has resulted in lower BC figures for most Sierra bullets. The only sure way to tell is to shoot the bullets at the same velocity and distance and compare results, like was said by one of the other posters, there will be some surprises both ways.