Modern cartridges are pretty much as per the `Ackley Improved` formula. P.O.Ackley realised - or discovered - that minimising body taper and increasing the shoulder angle allowed better performance with the same amount of propellent because of increased efficiency. Modern cartridge designs utilise minimal taper, high shoulder angles and shorter, large diameter cases.
Go to :
http://en.wikipedia.org/wiki/List_of_rifle_cartridges
Note the .243 Win and .243 Ackley improved designs side by side. In that particular case the body taper remains the same but the increased shoulder angle is obvious. The obviously modern cartridge design in that line-up is the .223 WSSM.
The WSSM cartridges are obviously modern in design but haven`t gained much popularity - mostly because they`re notorious barrel burners and also because they don`t really offer anything that other cartridges didn`t already provide. They are based on the WSM designs which, in themselves, were developed from 6mm benchrest designs and cartridges developed by John Lazzeroni. The theory is that a short, fat cartridge puts the powder as close as possible to the primer allowing for greater efficiency than a longer, smaller diameter cartridge. The .30 WSM ( for example ) offers .300 Win mag performance from a case that is barely longer than a .308 Win.
I`ve just found a nice picture to illustrate those points :
http://en.wikipedia.org/wiki/.300_Winch ... ort_Magnum
I can`t see any future for the WSSM calibres but hope that the WSM calibres receive the popularity they deserve.
Make a man a fire and he`ll be warm for a day. Set a man on fire and he will be warm for the rest of his life.
( Terry Pratchett )