I am floored that you are not following this. There are only2 variables to consider in the formula below.A combination ofSD and i (form factor) that equals BC.

SD/i = BC

I have been as clear as possible, as hasFariswm has been in his post.that the shape of the 180 and 150 grain bullets are the same so "i" does not change. The only variable that changes in this formula is SD so it should be fairly easy for you to follow.

We will start with the 180 grain 7mm bullet itsSD is .319.

.319/.52 = .613 BCfor the 180 grain bullet.

Now it is time for the 150 grain 7mm bullet its SD is .266.

.266/.52 = .511 BC for the 150 grain bullet.

I hope the light is on, if not I give up!

When Fariswm posted the quote below he was trying to accomplish what has just been clearly spelled out to you in great detail above. He is getting a high BC, easy to stabilize bullet,while also minimizing the bullets intrusion into the cases powder volume. The benefits can mean slower twist rates which combined with the additional powder capacity could yeild higher velocities.

Here is Fariswms post.

I hope this helps you grapple with this challenging concept.