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4/18/2021 9:59:29 PM
Posted: 6/2/2008 3:36:39 PM EDT
I picked this up the other day and was reading through the 308 pages.  They show (on page 457) a Spitz BTSP 165 grain with a balllistic coefficient of 0.520.  I was like wow that might be a great solution for long range shooting paper and actually using it on deer.  I look at the speer website and find the speer part number only to find out that the website claims that the balistic coefficient of 0.477.

Which do I believe?  I'm leaning towards the website because they are able to update it.  I was wondering if they can make that mistake what else did they typo in the manual.  Anyways does anyone know for sure which is correct.  Thanks
Link Posted: 6/2/2008 3:57:53 PM EDT
Find a third source and the suspect the one that's out of synch
Link Posted: 6/2/2008 4:35:58 PM EDT
Speer #12 lists .477 for that bullet.
Link Posted: 6/2/2008 5:07:40 PM EDT
As a former editor I will say that it is most likely a mistake...
Link Posted: 6/2/2008 7:06:46 PM EDT
Things that affect MEASURED BC:

Atmospheric pressure
Humidity
Temperature
Veloci­ty
Wind
Twist rate
Barrel condition
Pressure curve
Rifling type
Throat dimensions
Seating damage

You see how errors can propogate?  And it makes sense to note the above conditions when testing.  A good altimeter and hygrometer may be more useful than a chronograph, if you have the range.
Link Posted: 6/3/2008 6:51:57 AM EDT
About a month ago there was a thread here about speer redoing it's BC testing and some numbers were quite a bit higher than old manuals.  

I believe some posters said something like; salesmanship and playing with formulas to give big numbers.  kinda like the government and our inflation and other vital statistics.

ETA- I believe the poster in that other thread called Speer and got the we retested things answer from them.
Link Posted: 6/3/2008 11:32:44 AM EDT
Errors in published reloading manuals are certainly not unknown, that's why I ALWAYS have multiple sources for reloading info, so they can be cross referenced against each other to make sure you have a safe load.
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