Originally Posted by Marlinproud
Really? I cant believe its bc is so low considering its a longer bullet then the ballistic tip (bc .43) Will have to shoot both at the same velocity and see which drops more at long range.
The 150 grain E-Tip in .308 has a different boat tail angle and length, a different ogive, and is not really analogous to the NBT in any way, so I'm not sure why you think it will yield a higher BC. But probably the factor that increases drag the most is the pronounced shoulder or step discontinuity between the plastic tip and the front copper portion of the bullet.
In spite of some expectation that longer bullets should have higher BCs, this expectation is not realized in most copper bullet designs, even though they are roughly 20% less dense, thus ~20% longer for a given weight and diameter. For example, the 150 grain NBT has a BC advertised at 0.435. For comparison, the Barnes 150 grain TTSXBT has an advertised BC of 0.420 and the Hornady 150 grain GMX is advertised at 0.415. The Nosler claim of BC = 0.469 for their E-Tip would be exaggerated even if the shape was as aerodynamic as the comparable Barnes or Hornady copper bullets, but the shoulder and the suboptimal boat tail make it even worse.
Then you should consider that Nosler also exaggerates the BC of most of their Ballistic Tip bullets also. The published Litz measurements average around 6% lower than Nosler's claims, and the Litz measurement for the 150 grain NBT is a G1 BC of 0.406, much lower than the Nosler claim of 0.435. We measured the BC of the 150 grain NBT to be 0.381. We've corresponded with Bryan extensively to understand possible reasons for differences between his measurements and our and we've concluded that various factors probably contribute to differences between our measured BCs, including: 1) Different lots of bullets can vary dimensionally. We've seen 13% difference between the different lots of a given bullet (same rifle, same measurement method, same intial velocity). 2) Different barrels or changes to a barrel like polishing can shoot the same bullets with different BCs (same lot, same initial velocity, same measurement method). 3) BC can vary slightly with velocity.
Measurements by both Bryan Litz and by us suggest that Barnes measures relatively accurate BCs and that differences between Barnes' advertised BCs and independent measurements are both high and low so that the Barnes BCs do not seem to be systematically exaggerated as the Nosler BCs seem to be.