Question about Ackley Improved

I'm working with a 257 AckImp 40° that is chambered few thousandths deeper than the standard. I can form a false shoulder by expanding rhe neck on 257 Robert's cases and pushing the shoulders forward, or I can use 25-06 cases and set/trim the shoulder/neck back. I'm leaning towards using the 06 cases. Thoughts please.
 
I'm working with a 257 AckImp 40° that is chambered few thousandths deeper than the standard. I can form a false shoulder by expanding rhe neck on 257 Robert's cases and pushing the shoulders forward, or I can use 25-06 cases and set/trim the shoulder/neck back. I'm leaning towards using the 06 cases. Thoughts please.
06
 
I'm working with a 257 AckImp 40° that is chambered few thousandths deeper than the standard. I can form a false shoulder by expanding rhe neck on 257 Robert's cases and pushing the shoulders forward, or I can use 25-06 cases and set/trim the shoulder/neck back. I'm leaning towards using the 06 cases. Thoughts please.
As my brother Bean said, you will need to cut you necks, because, by the time you're done, the shoulders going to be a part of the neck. That said, there will be a well defined line, and if you tube mic it, you will get two readings. I believe it will be thicker at the top, and about mid neck, it will be thinner. The thin spec, will need to be the trim spec, to give you total neck contact.
The 257 AI is a peach of a round, and is under-rated. Hopefully, you have a long action.
 
Thanks. Now to find cases.. i "could" use 30-06 too. Do you think I will need to ream the necks tho... that's Ll that is holding me back,

As my brother Bean said, you will need to cut you necks, because, by the time you're done, the shoulders going to be a part of the neck. That said, there will be a well defined line, and if you tube mic it, you will get two readings. I believe it will be thicker at the top, and about mid neck, it will be thinner. The thin spec, will need to be the trim spec, to give you total neck contact.
The 257 AI is a peach of a round, and is under-rated. Hopefully, you have a long action.
Yup.1909 Argentine.. super smooth, strong,
 
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