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[Dan]

Don, you may recall my discussion at the other place about the effect of grease grooves and slight shoulder radius extending outside of the ogive break? This is one of those imponderables that I have no known reference that may resolve the question. The figure I quoted about the low value of shank drag was developed with jacketed bullets which are uniformly smooth in comparison to GG bullets.

Where I'm headed with this should be obvious I think. My mention of probable vortex generation due to grease grooves is the sum difference between otherwise comparable GG and PP bullets, and I suspect it to be quite substantial. Turbulence equals drag in the world of aerodynamics. Question I can't answer is just how much additional drag. Existing BC calculators do NOT take this into consideration, so the only way to fathom the spread is to shoot and compare. I read an illustration the other day about the comparative drag between PP and a .500 BC greaser. I don't believe such a thing has ever been cast of lead. I may be wrong about this but from what I've seen, an average of .300 BC is not to shabby with cast bullets and .400 is sterling. I truly do not know what the top of performance is or could be with large bore lead.

I have no scientific basis for this either, but my sense of it is a BC advantage for PP bullets otherwise equivalent to GG styles could run in the range of .025-.100. Don't quote me on that, it's just a gut feeling. Haven't even tried running the numbers in a calculator, but if someone can provide solid drop data and bullet specs along with MV for a couple of ranges, say 300 and 600 yds, it wouldn't be hard to crunch.