I added a plot of the shoulder area of a 338-66Sako (green and green dashed is AI) to the plot I had of other 338-06 based wildcats. The dotted blue line is the base of a 225 gr bullet in a normal 06 magazine. So in the case of the 340Howell and 338-66 with cases 2.6" long the net gain is very small compared to the gross the bullet simply sets deeper in the longer cases. For the Howell, Gibbs, PDK and the 338-66 you gain the most case by either going with a 210gr bullet or have a magazine and throat that allow you to seat the bullet out further.


My 340PDK is a 280Rem case. blown out to .458 40deg with a neck of .28" The 338-66 would have a neck of about the same length. What I have found with my case is that in a normal 06 magazine and 210gr bullet I gain 11% net capacity over a 338-06. Taking the 338-66 and comparing the drawing the normal shoulder would give a net increase of 11.7%. Much of the shoulder move is offset by reduced taper. The AI version would give 13%.

If the 9.3-66 brass ever makes it to the US it might make sense. But for now there are several opions to build a case with the same capacity. Z-hat, AHR and others sells 06 cylinder brass. it is 2.6+" straight. Get a rifle that allows you to seat out to around 3.6" set the neck at about .28" (the 225 is around 1.29" long). This gives you maximun net capacity. Then blow the shoulder out to .458 and 40 deg. Have a reamer made to take advantage of all this.

For now in my rifle I'll stay with my 340PDK.