The 6.5-06 A-Square is a centerfire rifle cartridge that originated as a wildcat, based on the popular .30-06 Springfield.
The neck is reduced to accept the smaller bullet, the shoulder is longer than that of the parent cartridge, and it has a 17.5 degree shoulder angle leading to the neck of the case, where the bullet is seated.
[1] The Ackley Improved version of the cartridge uses a sharper shoulder angle and has a case capacity of 72 gr of water.
There are smaller companies that custom load the cartridge[2] however, and hand-loading can be accomplished using the proper set of dies and using .25-06 Remington, .270 Winchester, or .30-06 Springfield brass and making the proper modifications to fit the 6.5-06 A-Square chamber.
After firing, the brass from the original cartridge (.25-06 Remington, .270 Winchester, or .30-06 Springfield) will be fire-formed to the exact dimensions of the 6.5-06 A-Square chamber.