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Forming 257 Roberts from 7x57 Mauser?

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Olympus

Olympus

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Has anyone done this and could give me the run-down on the process? I'm mainly concerned about if I will have to turn or ream the necks. I can't seem to find 257 Roberts brass at a reasonable price. I know you can neck up 6mm brass, but I can't seem to find much of that reasonably priced either. I found some factory new 7x57 brass for $50/100 and was thinking about giving that a try, but wanted to know more about how difficult it would be or if I should just wait to find some 6mm brass.
 
You will not be forming, you will be necking the case down. this question is identical to another thread here or on another forum. The 7mm57 family of cases has the same case length and shoulder angle as the parent case. When necking a case up or down reloaders assume the neck gets thicker and or thinner. I do not assume, when I neck a case neck up and or down the neck gets longer and or shorter and then it gets really complicated. When the neck gets shorter the shoulder gets longer, when the neck gets longer the shoulder gets shorter.

And then there is that other part; when the neck gets shorter part of the neck become part of the neck. Going the other way; when the neck gets longer part of the shoulder becomes part of the neck.

So you have a choice; neck up and or down. But if you are talking about forming purchase a forming die. I form 257 Roberts from 30/06 cases. I have paid from 1¢ to 8¢ each for 30/06 surplus cases. When forming a case there are no way the cases can get expensive. By the time a reloader pays $87.00 for 100 275 Roberts cases he could be the proud owner of a forming die.

F. Guffey
 
Forming dies: If I had but one forming die it would be a 308 W case forming die. If I only had two forming dies the other would be a 243 forming die. My favorite forming die is a short forming die.

F. Guffey
 
I'm even more confused than I was before.

It was my understanding I could use a FL sizing die in 257 Roberts on 7x57 brass.
 
Hi Olympus,

I have never dealt with changing brass from one caliber to another, but I do like 257 Rob and AI. From the Forster website:

"Use factory brass or resize 7X57 brass in a 257 Roberts full length sizer die. Or form from 30-06 with a form die set. "

I search for dies for the 257 and got:

http://search.forsterproducts.com/specs.asp

I hope it helps.
 
I never done it. From SAAMI drawings of both, use a FL sizing die in 257 Roberts on 7x57 brass. Load a round and make sure neck diameter is not larger than .290" If neck is ok, fire form with bullet jammed into rifling. If neck is to large in diameter, outside neck turn , before loading.
 
Best thing for you to do is to find Roberts NEW empties on line!
They ARE there and you can save yourself quite a bit of headache
 
Zeke/PA said:
Best thing for you to do is to find Roberts NEW empties on line!
They ARE there and you can save yourself quite a bit of headache
Click to expand...
Only ones I can find are Nosler brand and those are ridiculously expensive.
 
rabid wombat said:
Hi Olympus,

I have never dealt with changing brass from one caliber to another, but I do like 257 Rob and AI. From the Forster website:

"Use factory brass or resize 7X57 brass in a 257 Roberts full length sizer die. Or form from 30-06 with a form die set. "

I search for dies for the 257 and got:

http://search.forsterproducts.com/specs.asp

I hope it helps.
Click to expand...
This was what I thought the process was. I have a full length resize die for 257 Roberts. Just wanted to know more before buying a bunch of 7x57 brass. Thanks!
 
From Redding: "Below are a few examples of commonly formed cartridges listed with their parent case and the forming dies that are required. We make many others and they all come with complete, easy to follow instructions. If you need to form a caliber that is not listed, simply write us or call explaining what you would like to do.
NOTE: Full length resizing is a necessary final operation after all case forming to insure proper chambering."

See p23 of their catalog:

http://www.redding-reloading.com/images/stories/2016Pressinfo/Redding_2016.pdf
 
Still confused. So I need a forming die AND a full length resizing die?
 
Best I can tell, you just need to resize 7x57. You will need to form 30.06. Please realize, I have no experience with this. I would call one of the die companies in the morning and get the straight poop. Then it becomes a math game. Do forming dies and cheap brass cost less than sort of expensive brass and cheap dies - this will come down to how many rounds you expect to do. Sorry, I can not give you the right answer.
 
I have a worse problem than that in that I have a 257 Ackley so I have to find or load .257 Roberts and fire form it in the Ackley chambered Hi wall.then trim and reload that.Is there an easier way me wonders?
 
I use to own a 6mm Remington and still have the brass. I have a very modest yet sufficient number of .257R cases but created more by running the 6mm cases through the .257R die. Never tried it with the Mauser case and don't have any Mauser brass.
 
Several years ago I ran short on 6mm Remington brass but had an excess of 7x57 brass. So I lubed a couple dozen 7x57 cases, ran them through my 6mm sizing die, trimmed them to length, and was all set. Been using them ever since. It really is as simple as that!

35W
 
I have sized 6mm Rem from 7mm x 57 mm with no problems ...

It would be a simple check to compare a factory round outside diameter with a 7mm case resized to .257 Roberts with a bullet seated .... it should be very close to .290" with the bullet seated ....

Your chamber will be the gauge that needs to be fit for it to work as it should ....
 
I go from 7.62x51 to .243 by going:
7mm 08 trim die
.243 trim die
.243 full length resizer.

I'd get a .257 Roberts Trim die to a .257 full length resizer from a 7x57.
The last thing I would advise is anneal, anneal, anneal prior to working any brass.


kwg
 
I'm even more confused than I was before.

It was my understanding I could use a FL sizing die in 257 Roberts on 7x57 brass.
Click to expand...

That happens all the time, I said when you go from 7mm57 to 257 Roberts you are not forming the case; I said you are necking the case neck down.

After that there was a rush for the 6mm Remington. Again there is no excuse to get confused, when going from 6mm Remington to 257 Roberts you are necking the case us; again, you are not forming the case.

When a reloader is necking a case up and or down he is operating under RCBS rule (footnote) *1.

F. Guffey
 
Forming 257 Roberts from 7x57 Mauser?

--------------------------------------------------------------------------------

Has anyone done this and could give me the run-down on the process?
Click to expand...

You will not be forming, you will be necking the case down. this question is identical to another thread here or on another forum. The 7mm57 family of cases has the same case length and shoulder angle as the parent case. When necking a case up or down reloaders assume the neck gets thicker and or thinner. I do not assume, when I neck a case neck up and or down the neck gets longer and or shorter and then it gets really complicated. When the neck gets shorter the shoulder gets longer, when the neck gets longer the shoulder gets shorter.

And then there is that other part; when the neck gets shorter part of the neck become part of the neck. Going the other way; when the neck gets longer part of the shoulder becomes part of the neck.

So you have a choice; neck up and or down. But if you are talking about forming purchase a forming die. I form 257 Roberts from 30/06 cases. I have paid from 1¢ to 8¢ each for 30/06 surplus cases. When forming a case there are no way the cases can get expensive. By the time a reloader pays $87.00 for 100 275 Roberts cases he could be the proud owner of a forming die.
Click to expand...

I'm even more confused than I was before.

It was my understanding I could use a FL sizing die in 257 Roberts on 7x57 brass.
Click to expand...

Quote:

After that there was a rush for the 6mm Remington.

There was no rush involved .... I slowly SIZED 7x57 brass into 6mm Rem .... !!
Click to expand...

JimKirk, He was confused when he discovered he was not forming cases. There should be nothing confusing about necking a case up and or down; it would help if he understood RCBS footnote rule *1, that is when RCBS says no forming die is necessary and then it goes on to say something about 'all that is necessary is to size the case with a full length sizing die in final caliber'.

F. Guffey
 
Nothing relevant comes up using that search criteria on YouTube.
Click to expand...

Olympus, and no one ask you what die you are using nor did they mention the manufacturers date. In among the circled number footnotes listed by RCBS at least 2 of the 10 rules list the date of the die.

Hornady made an expander plug that started the expansion with a triangle shape and finished with a full circle. I did not get into it but some thought that was 'being kind to the case neck'. Hornady sold a lot of the expanders to RCBS die owners and then RCBS started putting a longer taper on their expander buttons/plugs; and that is the reason for some of the dates; meaning order a new plug if your die was made on or before.

And then RCBS has stopped using manufacturers dates on the top of the die, many years ago they stopped somewhere around 'N' in the early 60s.

F. Guffey
 
And then someone should wonder why there was no thought given to the sizer plug shape before millions of dies were made. It was all in the name of the die; the die was identified as a sizing die. When sizing a fired case the sizer plug does not touch the case neck until after the ram reaches the top of the stroke and is lowered. That means the sizing plug was pulled through the neck, it was not pushed. And then there is that other thought; the stem on the early RCBS dies was (in my opinion) to small in diameter to push the sizing ball through the neck when necking a case up. When the new models came out the diameter of the sizer ball/primer punch stem was increased.

Reloaders with Herter sizing dies never knew there was a problem. And then Hollywood Gun Shop went through some changes, they had sizing die with an integral stem. If a stem is available some would risk pushing it through the neck but serious thought went into pushing the stem into the neck when destroying it was poasible.

F. Guffey
 
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