Re: Different shape boattails effect on BC
There are sweet spots to boat tail angle.
An example with angle changes to 6mm 105 Lapua,while holding same weight:
BCbyED= ICAO G1 BC @ 3Kfps by angle changing end diameter
BCbyBTL= ICAO G1 BC @ 3Kfps by angle changing boat tail length
BTA BCbyED BCbyBTL
4 0.485 0.513
5 0.490 0.506
6 0.493 0.500
7 0.495 0.495
8 0.495 0.490
9 0.494 0.485
10 0.492 0.481
11 0.489 0.477
12 0.486 0.474
(do know how to space)
There there can be an angle with the best overall balance in origin. Lapua chose 7deg.
The trend holds but shapes differently at other velocities and air densities.
I can't calculate rebated boat tail results. They do not increase BC over linear angles, and if I remember right Litz found they did not hurt BC much if any either.
The benefit they seek is in accuracy from cleaner release at the muzzle.