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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
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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