Agreed but case shape does affect velocity. Familiarize yourself with the Venturi effect... Ackley's shoulder and neck expound upon this. Otherwise you wouldn't see the tremendous velocity gains in cases containing 10 grains less powder.anything on the 7x57 and 250/300 parent cases will have a big gain due to a significant gain in case capacity when the outdated taper is blown out of them on fireforming.
the 308 will gain far less percentage wise.
there are those who claim that the smaller capacity cases can beat the bigger capacity due to being more efficient or some other such tripe.
i recall one who told me that the 250/3000 ackley is faster than the 25/06 ackley because it is more efficient.
case shape is irrelevent to velocity, but capacity is relevent..
as long as you use the correct burning rate powder for the job.
the 7x57 ackley has close to the same capacity as the std 280 rem.
translated into english, at the same pressure and with the best powder, velocities will be the same.
if you want to have to fireform cases for std 280 velocities, go ahead and do the extra work, buy the more expensive dies, and burn out a barrel sooner.
the 280 ackley will be between the std 280 and the 7 rem mag, because it is between them in case capacity.
as a straight dingo gun it would shoot pretty flat with 120 gn vmax or the bit harder 120 gn sierra soft point.
140s of different construction offer a wide range of game opportunity with the same zero and shooting nearly as flat.
then up to 160s of various construction.
after that you have a 375.
such a rifle with a 24" shilen no 3 profile barrel or similar will do a lot of jobs very well.
fir a pure dingo only gun, a 25/06 or a 6mm ackley rem might suit more, but are very specialized.
the 280 or 280 ackley are just so versatile.
120 gn bullets have sectional density of 50 gn 30 cal.
140s the same s.d. as 165 gn 30 cal.
160s the same as 190s.
a nice compromise.