Resizing brass to 257 Robert's question.

I have done some reforming, but hesitate to give specific instructions because I have not done this one, and the ones I have done taught me there are some subtleties to be aware of (especially neck wall thickness). That being said, this looks like a pretty easy one. 7 x 57 Mauser is the "parent case". It is described in my copy of copy of Handloaders Manual of Cartridge Conversions. I will check back after others comment and can quote the book for you. Don't want to make this too long to start. Have you done any reforming before?

6 mm Remington brass would be the easiest.

Here's a description on what it takes to form this brass.


https://castboolits.gunloads.com/showthread.php?248513-Making-257-roberts-brass/page2

I would assume it would be easier to find 7x57 brass than 6mm Remington brass, but this day and age, finding any might be tough.

6 rem works the best, no worry about necks being to thick after sizing, next would be 6.5x57 brass. And 7x57 will work fine but necks can be a bit tight. Grafs has had brass in stock.

You should be able to find some 257 Roberts brass if you're not in too much of a hurry. But I think the parent case is the 7 X 57.

Easiest way currently to acquire.257Roberts brass is to run 7mm Mauser brass through a .257Roberts sizer die.

Grafs.com has 7x57 (Mauser) brass in stock. Item #PPC7x57. $32.99/50
PPU brass is quite good. Likely no need for annealing before or after. (I never have...)

I’ve got a few pieces of .257 I formed from 7x57, 8x57, 6mmRemington.
Mostly, I bought 160rds of Winchester 117gr PowerPoints on clearance at an Ace Hdwe going out of business for $4/box. (1983). I was also gifted 10boxes of Federal Premium once fired brass. It’s amounted to a lifetime supply as it was 38yrs ago.

Only size the brass until it easily chambers in the rifle. My Lyman die set sizer will significantly over-size the cases if totally sized. My Lee set is nearly ideal...

Best powders are IMR4350 and H4350. IMR and H4831 are close. H414 and H380 also get honorable mention.
If rifle is a custom build on a military action, consider Hodgdon’s online data as firm maximum loads.

Pics needed!!!

Some good input here. So here is what the book says (Handloaders Manual of Cartridge Conversions):
"Make from 7 x 57 Mauser. Anneal case neck. Size in Roberts die with expander removed. Trim to length.
I.D. neck ream. Chamfer. F/L size."

So there are several cases based on 7 x 57. Necking down or necking up is your choice. Necking down will thicken neck and lengthen case in my experience. Necking up will do the opposite. (This is for cases with the same shoulder angle- 6mm Rem is different than 257 Roberts). The difference may be negligible and could benefit you or work against you depending on the chamber. Different brands have different brass thickness. I have some PPU that is thin in some cartridges, so PPU 7 x 57 might work nicely for you without reaming. Depending on die, you might end up with a dimple in the neck that can be fire formed out when necking down. All else being equal, I'd rather neck up. It's a lot of trial and error (especially with removing or leaving expander ball in). A tapered ball can help a bunch. Just make sure the end product is in SAAMI spec, it chambers easily, and you work up the powder load to check for pressure signs. Good luck.

You shouldn't get stuck cases, lube inside the neck tho.

I've gone both ways without issues. 30-06 to 25-06, 223 to 20 Practical (over 3,000 rounds without a problem), then I got a few 6CM in a batch of 6.5 CM so I just ran them thru 6.5 die with no problem.

Highland Lofts said:

Lots of good information here, thank each & all of you for your responses. I do have some 6mm brass and some 7x57 brass. The 7x57 is easier to find.
I will try the different calibers and see what works the best.

Do you guys get stuck cases reforming for the 257?
I use the home made lube, 10 to 1 red can of HEET (dry gas) and liquid lanolin. I also have the Redding dry neck lube and I just bought some imperial neck wax.


This will be a fun little project.
Merry Christmas to all of you.

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I would case form with a heavy libe like the lee paste or redding sizing wax. I use the lanolin mix for bulk resizing. I would also leave out the expander as getting out a stuck case is way easier that way.

I have, as I stated in an earlier post formed .257brass from all other possible x57 cases. (Yes, even ran across a 6.5x57 case, once!).

None thickened the necks to point of needing reamed (or better, turned). Even several from 8x57 brass. (Not mil surp though). Several were lost due to case buckling at shoulder. Imperial case lube prevents this, as well as shoulder dents.

However, I tried my hand at reforming from .30/06. Not a happy result. Neck folding, shoulder collapse, and few I did form were too thick in neck to use without reaming or turning.
Your results may be different.

@Highland Lofts
PM me your address and I'll send you some .257 brass.

O/P, contact RCBS and see if they make a tapered expander button for .257. It makes the necking up operation much smoother going from 6MM Rem. to 257 R. I use tapered neck expanders in my 358 Win. (308 Win to .358) and 338/06 (30/06 to 338/06)and 243 to 260 Rem. All with tapered expanders.

Bandit67 said:

View attachment 1047296

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That's a handy book, right there

Ironicaintit said:

That's a handy book, right there

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If you have a ollies close by they have a reprint for under $10, think I got my last one for 4.99 I need to buy a few more next time I'm there, they make good gifts for reloaders

I used to make 25-06 out of 30-06 and 270. I make 260 Remington out of 243 normally, because 243 brass is cheaper. Never had any problems doing so. Main rule is to use enough lube.

Got it!

Powder Valley has some 7x57….

https://www.powdervalleyinc.com/product/prvi-7x57-mauser-50/

rabid wombat said:

Powder Valley has some 7x57….

https://www.powdervalleyinc.com/product/prvi-7x57-mauser-50/

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Dang that's a good price, I really should order a few hundred.

troy fairweather said:

Dang that's a good price, I really should order a few hundred.

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Don't hesitate.

Bandit67 said:

@Highland Lofts
PM me your address and I'll send you some .257 brass.

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And the OP found the easiest way to find scarce components... Ask where to find them on the high road. One of us will be sure to have some to share.