Quote History Originally Posted By Bruw:
"A 140gr 6.5mm bullet scaled up to 30cal is a 230gr bullet, so the 230gr bullet is the proper bullet to compare to a 140 6.5mm for long range performance not a 175. "
What measurement or criteria was "scaled up" to come to this conclusion?
Thank for the info. Really great post.
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It is the work of Bryan Litz.
It goes like this: (not the work of Litz)when you scale up something by a linear dimension(like caliber) the volume goes up with the cube of the linear change, the weight goes up with the volume.
The linear scale factor between calibers 7.62 and 6.5mm is 7.62/6.5=1.1723. So the 7.62 is 1.1723 times bigger in diameter than the 6.5mm.
The the scale factor for the weight of the bullet will be 1.1723³ which is 1.6111. 1.6111 x 140gr = 225.6gr
130gr 6.5mm scaled to 7.62 would be 1.6111 x 130gr = 210gr
123gr 6.5mm scaled to 7.62 would be 1.6111 x 123gr = 198gr
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6mm scaled to 7.62 would be 7.62/6 = 1.27. For weight it would be 1.27³ =2.048 scale factor so.....
108gr 6mm scaled to 7.62 would be 2.048 x 108= 221gr
115gr 6mm scaled to 7.62 would be 2.048 x 115= 235gr
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6mm scaled to 6.5mm would be 6.5/6 =1.083... for weight scale factor 1.083³ = 1.2714
108gr 6mm to 6.5 would be 1.2714 x 108 = 137gr
115gr 6mm to 6.5 would be 1.2714 x 115 = 146gr
So you can see anything under 200gr in 30cal is not a fair comparison vs. any of these sleeker calibers. To be fair you scale up the same shape bullet to the caliber. Obviously the shape of the bullet has a huge impact on how well it cuts through the air, you want the same shape and proportions as the other low drag bullets, in 30 cal those proportions result in bullets that are 215-230gr(in copper jacket lead core type).