What are the BCs for cannon rounds?

[Trooper]

The one thing that the 6.5mm has going for it is nearly a perfect BC. Same for the .338 (8.6mm - .338LM or 8.6x70, .338NM or 8.6x63). Both calibers have a BC of .600 or greater.

What is the BC of the cannon rounds (like 20mm, 25mm or 30mm)? Or the larger rounds like the CG 84mm RR or the 105mm and 155mm?

While the military has centered on the 105 and 155 (and 120mm for the M1 tank), and now the 84mm RR (replacing our other anti tank rounds), the smaller rounds are still in flux. Which one would make the best - 20, 25 or 30mm?

[stanc]

"Ballistic coefficients are based on standard projectile's that, by convention, are 1" in diameter and weigh one pound. It therefore has a sectional density of 1. As the standard it is declared to have a ballistic coefficient of 1. Projectiles that are slowed faster by drag than the standard projectile is, will have BC's lower than one. Those that are not slowed as quickly will have BC's greater than 1 (artillery shells, for example)." http://www.shootersforum.com/ballistics-...post464902

[dmsims21]

Thanks, for the explanation Stan. I always wondered how a 50 BMG had a BC greater than 1.
I thought it was more of a physical property instead of a power factor (either the bullet slows down faster or slower than the reference object.)

[65Whelen]

The one thing that the 6.5mm has going for it is nearly a perfect BC. Same for the .338 (8.6mm - .338LM or 8.6x70, .338NM or 8.6x63). Both calibers have a BC of .600 or greater.

What is the BC of the cannon rounds (like 20mm, 25mm or 30mm)? Or the larger rounds like the CG 84mm RR or the 105mm and 155mm?

While the military has centered on the 105 and 155 (and 120mm for the M1 tank), and now the 84mm RR (replacing our other anti tank rounds), the smaller rounds are still in flux. Which one would make the best - 20, 25 or 30mm?

Dang, I was hoping you had a new build in mind. What size mag well would you need for a 30mm round? Course you might run into some pressure issues. lol