i was reading a long range rifle text and they mentioned the Greenhill Formula as one way of selecting a projectile. The formula is ((bullet diameter) x (bullet diameter)) x 150 / rate of twist.
For example for my 6.5x47L with a 1:8 rifle twist that would be:
0 .264 x 0.264 = .069696
.069696 x 150 = 10.4544
10.4544/8 = 1.30 inch
When i look at the Lapua projectile site data i find that both their 123gn and the 144gn projectiles have a length of 1.3 inch
i never hear anyone discussing use of 144gn projectiles in the 6.5x47L
Wondering why that is? Has this formula not proven well in practice? For shooting paper targets, Is there a better way to choose projectiles in addition to BC? thank you
For example for my 6.5x47L with a 1:8 rifle twist that would be:
0 .264 x 0.264 = .069696
.069696 x 150 = 10.4544
10.4544/8 = 1.30 inch
When i look at the Lapua projectile site data i find that both their 123gn and the 144gn projectiles have a length of 1.3 inch
i never hear anyone discussing use of 144gn projectiles in the 6.5x47L
Wondering why that is? Has this formula not proven well in practice? For shooting paper targets, Is there a better way to choose projectiles in addition to BC? thank you