Re: Ackley Headspace Gauges
As for why the different lengths.
Different lengths certainly do help prevent the act of trying to insert cartridge "A" into gun "B".
There may be another reason though.
As we discussed earlier, the case body takes material from the neck to inflate the case and alter the shoulder angle. How much neck gets left over becomes a function of the case body diameter and length before the shoulder. Shoulder angle also plays into this. An aggressive shoulder angle is going to be shorter in length than a shallow one.
I think PO Ackley may have wanted to have his neck lengths more uniform/symetrical from one cartridge to the next. Meaning a 25-06 should look proportionally similar to a 30-06. This would be so that bullets have sufficient support along their bearing surface by the neck. That being said the case cartridge length would have to be altered to achieve this due to the larger bullet diameter. (more circumference eats more material, ='s a shorter case length)
I don't know this for sure, but it seems to make sense.
If not, you'd end up with the "Ackley/Gibbs inbread thing" I described earlier.
Last edited by NesikaChad; 08-31-2010 at 05:51 PM.