Head space on a 257 Ackley improved

[brstevens]

Can a standard 257 Roberts Head space gauge be used to Head Space a 257 AI?

[Wildcat]

brstevens,
The standard 257 Roberts headspace go gauge is used as the no go gauge in an Ackley improved chamber. This is because most properly cut Ackely chambers are .004" to .006" shorter than the parent case chamber. This provides for less case stretching and greater accuracy when firing cartridges loaded in the parent calibers brass, and ensures a crush fit when fire-forming cartridges without having to set bullets out long to jam into the lands to hold the case in place.
To complete the job properly, I recommend you also pick up a 257 Ackley improved go gauge. That said, there are alternative ways to accomplish this task if you don't want to purchase an Ackley improved go gauge. I will let those individuals more familiar with those techniques chime in as I only have experience doing it this way. I hope this response was of some help to you.

-Wildcat

[yobuck]

Head space is what head space is regardless of case shape. The mere fact that an AI case differs from a standard one dosent
affect that part of the case where headspace is checked, the case head itself.