Thread: 35* long neck 7 SAUM based on WSM

Originally Posted by grandpamac

Greetings,
.270 WSM base measured 13.93 mm (0.5485 inches) and the 7 mm SAUM base measured 13.85 mm (0.5455 inches) for a difference of 0.08 mm (0.003 inches). There is a way that you could form a case without butchering a die. You can sit the case on top of the shell holder (using a .223 shell holder would be a good idea to make things more stable) and run the case into the die a little at a time until you get what you want. You will have to knock the case out of the die with a rod and a small hammer, a rod from a small calibre Lee Loader would be ideal. Obviously you will need to remove the decapping stem first.

I wouldn't expect to get extra velocity or lower pressure at the same velocity from the steeper shoulder. This is often claimed for wildcats with steeper shoulders but actual comparisons using pressure testing equipment have failed to show any improvement. Wildcatters discussing their creation often show as much objectivity as a man talking about a grandson who has been named after him. At best you will get 7 mm SAUM performance at 7 mm SAUM pressures or higher performance at higher pressures.
Regards Grandpamac.

Thank you grandpamac. The plan is do butcher/shorten the die, if I can get a cheap one somewhere. Based on your measurement around the base, the measurement from the shoulder down could even be closer. I think a lot of the wildcat gains is a result of increased case capacity, but I think a shoulder angle do contribute to the efficiency of a case. This is partially based on my understanding and experience in water and pump design and friction losses etc. The way I see it is that a flatter shoulder helps with the ignition, but that a sharper shoulder helps with the pressure flow. Or at least that is theory.