257 roberts from 7x57 or 6mmRem??

[358WCF]

6 Creedmoor rub through the 257 die is what I done once. Fire form and move on.

Wasn't the case a bit short? Creedmoor is 1.920", Roberts is 2.235"

 

[std7mag]

Chuck Miller said "Not a fan of fire forming" If you resize anything to 257 Roberts AI, you will have to fire form. Or am I missing something.

Yes, even if you neck down 7X57 Mauser to 257 Roberts, it will fire form to your chamber.

I use the 7X57 Mauser PPU brass for my 257 Roberts and AI.
I've taken several deer while fire forming to AI using "standard" 257 Roberts loaded with 115gr Nosler Ballistic Tips.

 

[Charlie Brown]

257 Robert's ammunition is very hard to come by.
And yes that is how the ackley shoulder is formed or it was intended.
Shoot factory loaded ammo and blow out the shoulder ..

Since 257 Bob loaded ammo is scarce. We use alternatives..
7x57 brass easy to form..neck down,trim, load and fire.

If you are quite handy it can be formed from 270 winchester,.6.5x57, and even the 30-06 case's..

Just how willing are you.

Fortunately the fellow I got the rifle from included some brass to get me started. But was eyeing some ammo on gunbroker to get a little extra.

 

[Walt Krafft]

I got some Bertram brass a couple of weeks ago. Pricey but easy.

 

[STX]

I’ve resized a lot of 257 brass to 6mm Rem……don’t see why you couldn‘t go the other way!

 

[Kittitas George]

It has been a while but I used some new 7x57 Norma brass to make 6mmAI. No problems, necked to 6mm then fire formed to 6mmAI. Forming loads were accurate enough for gophers and prairie dogs.