I'm looking for .45acp mold. I've found a few and noticed the "Ballistic Coeff" vary from .120 to .180. I shoot paper and rotating targets. How much difference to the Ballistic coeff make. Which is better the lowend (.120) or highend (.180)?

For 45acp, its not going to matter one bit.

Your bullets are moving too slow to worry about supersonic issues.

Your ammo from a 1911 or carbine is only going to be doing around 1100fps or less...100yds or shorter.

Its far more important at this point to find a bullet with a good nose on it that allows for reliable feeding and cuts a clean hole with paper than anything else.

Just my $.02 (having reloaded 2K rounds of 45ACP over the last year or so)

Agreed. While higher numbers are better, accuracy and reliability are more important at .45 ACP ranges. Let's fire a 230 grain bullet at the standard 850 fps for pistols. A .12 BC gives 801 fps at 50 yards while a .18 BC gives 817 fps at 50 yards. The difference in total drop is less than a 1/10th of an inch, about 6.2" and both will be 1.2" high at 25 yards.

BC starts having effects further out. Your bullets have a 1.5X difference which is the approximate difference between round nosed and pointed flat based 180 grain .308 bullets. Very simply, the pointed bullet is going as fast at 300 yards as the round nosed bullet is going at 200 yards when they are fired at the same muzzle velocity.

Bye
Jack