Speer BCs - How accurate are they ?

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secondtry
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Speer BCs - How accurate are they ?

Post by secondtry »

Specifically the 7mm 145gn Boat Tail Spitzer.

I am looking for something to let a 10" twist 7.08 reach out a bit further and the advertised specs of this bullet make it a candidate.

Speers current claim is .472.

Given that "truth in advertising" appears to have a led to a reduction in claimed BCs for many bullets on the market,
particularly NBTs, I am wondering how accurate Speers .472 is.

Does anyone have any info on this ?

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stokesrj
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Re: Speer BCs - How accurate are they ?

Post by stokesrj »

I used to believe that marketing drove the decisions to assign BCs, and I’m sure in some cases it does. But now that i’ve had my Doppler Radar for a few years and am able to measure actual vs claimed BCs I think it is more an issue of mathematics, or more correctly the formula for calculating a BC from the shape of the bullet which was the common practice until Brian Litz started using Doppler to measure actual BCs. This forced many manufacturers to follow suite and notably Hornady lead in accuracy because of their investment in a serious earth stabilized Doppler system that could measure the speed decay over a longer flight distance. Speer is behind in this game. The bullets Ihave measured from Speer are from my stocks which are quite old, so I’m not sure it would be the same for new stock. These have run 8-10% below advertised BCs.
Robert J Stokes

secondtry
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Re: Speer BCs - How accurate are they ?

Post by secondtry »

Thanks Bob.

In my old loading books, Speer claim .502 for this bullet. That has since been revised to .472, but I don't know what the revision is based on.

My other possibility is the 150 Ballistic Tip with a measured BC of .442. Visually the Speer appears to have a gentler ogive and a longer boat tail but no sharp poly tip. I can also get more starting velocity with the 145g

Looks like my only option may be to order some, work up a load and find somewhere I can shoot them at 600 yards.

Or maybe I'll adopt plan B and not bother :lol:

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