Fire forming 7-08 cases to 7X57

[normmatzen]

Has anyone ever heard of fire forming 7-08 cases out to 7X57?
I know the 7-08 is shorter, but I don't know if it would grow longer during fire form.
Good 7-08 cases are easier to find than 7X57 and run at higher pressure.

 

[KMart]

I think your better option is 30-06. I made some years ago. Imperial Wax and slow press strokes reformed them fine. Use a body die or file type trim die for first pass.
The downside is a lot of trimming, annealing and maybe neck turning.
Or, upsizing 6mm Remington, 257 Roberts necks

 

[Brians356]

The easiest option is to form from 30-06 in the RCBS Form and Trim Die #13865.

 

[Ackman]

Has anyone ever heard of fire forming 7-08 cases out to 7X57?
I know the 7-08 is shorter, but I don't know if it would grow longer during fire form.
Good 7-08 cases are easier to find than 7X57 and run at higher pressure.

Fireform a case and make it .200" longer....how you gonna do that?

 

[bobm]

"Good 7-08 cases are easier to find than 7X57 and run at higher pressure".

That statement is not true in so many ways. ???

Powder Valley shows PRVI 7x57 brass in stock now at $44.00 per 100. That is a great deal on really good brass.

Easiest option??? 1-800-227-4299. Operators are standing by. ;D

 

[normmatzen]

BOBM,

Enlighten me.

 

[bobm]

What's to enlighten? Firing short brass in a long chamber is plain just not smart. Your asking for stretched brass in the head area on the first firing. You will end up with weaker short neck brass. Your chamber neck is now exposed to hot gas and flame essentially becoming part of the leade. This brass will fail quickly with repeated firings and never grow to nominal 7x57 length.

I have a M77 Ruger in 7x57.

 

[Brians356]

What's to enlighten? Firing short brass in a long chamber is plain just not smart. Your asking for stretched brass in the head area on the first firing. You will end up with weaker short neck brass. Your chamber neck is now exposed to hot gas and flame essentially becoming part of the leade. This brass will fail quickly with repeated firings and never grow to nominal 7x57 length.

+1 !!!

Fireforming is for cases which will already headspace on the shoulder (for rimless and beltless cartridges). Example is Ackley improving, when the case will make at least some contact at the shoulder/neck junction, and ideally the chamber is 0.010" shorter than the parent chamber so that there is a crush fit at that junction. Or, fireforming a 7mm-08 case in 308 Win chamber, to open up the neck (just in case you can't find any good 308 brass, I suppose.) But your 7mm-08 shoulder is 0.116" short of contacting the 7x57mm chamber's shoulder. Even fireforming "bulletless" would be ill advised. It might form the case without a mishap, but I would expect stretching in places you don't want stretching (in the head area), results case-to-case will probably be inconsistent, and they will all probably finish up way too short in OAL.

PS The max case diameter of 7mm-08 at the head (0.200" from the base) is .4703", and the 7x57mm is .4711". So even if you start with fired 7mm-08 brass, they probably won't be a snug fit at the head in the 7x57mm chamber, so the excess headspace at the shoulder remains a problem.

 

[KMart]

Another option for high end brass is at Huntington Die Specialties. They have Norma 7x57 brass in 100 ct bags for $115.

Yes, some say it is soft. Others say it is great.

 

[AZ BR FAN]

I have 340 W-W 7mm mauser brass brand new my email is arizdc55@gmail.com

 

[normmatzen]

Thank you BRIANS356!

The only brass I have ever modified was 200 6BR cases fire formed to 6BRX and I fully understand that process. I have also converted 6.5-284 Lapua cases to 284 WIN.

I have read a lot about the limitations of the 7X57 and understand most of it is due to lawyers and fear of the m 93 Mauser.

But, I would like to convert a high pressure case ( I now believe the 30-06 is the best bet) to 7X57 to take advantage of heavier loads. To my knowledge, the limit on 7X57 cases is 53k psi (at least in Europe). The details you presented was exactly what I was looking for, not trash talking from someone who doesn't know any more than I do on the subject.

 

[Brians356]

I'm flattered, but I am far from the most experienced here WRT case reforming.

Re: Stronger brass, you have nothing to fear with 7x57mm brass, it's a stout as any other case in the class. The lower max pressures encountered in load data are strictly down to the many weaker Mauser actions in circulation, as you pointed out. The brass itself is as stout as any of the cases based on the 7x57mm, like 6mm Rem and 257 Roberts.

Your problem is not finding strong brass, it's finding load data which is not limited to traditional pressures. Hornady 3rd Edition listed (for Ruger M77 w/ only a 22-in barrel) 140-gr loads up to 2900 fps (53.0 grs IMR 4350), which is stepping out, at far higher pressure than the typical 46,000 psi limit, believe me. (Speer #10 listed 2735 fps from the same 22-inch M77, but chose to limit pressure to only 50,000 psi.) With a longer barrel you should easily be able to get 3000+ fps with no special concern for any 7x57mm brass, just monitor pressure signs as normal while working up.

 

[normmatzen]

thanksagain Brian,

I must admit, I have already pushed the "limit" a bit. As my action is a stout VZ24 M98, I regularly push 140 gr bullets out of a 24" barrel at 2900 fps and 162 gr at 2650.

I mainly was curious if there was some mechanism in fire forming that I wasn't aware of. Your answer convinced me that my hunches were correct.

 

[jdh47]

I would try .270 brass to 7x57 or just get 6mm rem. and just expand the neck.

 

[normmatzen]

Jdh47

Thanks, as I have experience expanding 6.5 mm brass up to 7mm, this sounds like the elegant solution!

 

[Witchhunter]

I would buy the brass from the guy from Arizona if it were me. That way it will say 7mm Mauser or 7x57on the headstamp. Or, call Powder Valley and get some PPU coming. Simple solution.

 

[normmatzen]

Witchhunter,

You may not have noticed, but I have plenty of PPU cases as well as some W-W and even some made from 270 WIN.

I was more interested in using cases inherently better as to max breech pressure.
I think the PPU cases are good for 53k psi, but I want the pressure a 30-06 is capable of, or a 270 WIN.

 

[JRS]

Have you considered the CIP pressure Norm? CIP shows 56,565. SAAMI usually shows something lower due to it's original use in the older and weaker actions. Much like the 6.5x55 and 45-70.

 

[Brians356]

I was more interested in using cases inherently better as to max breech pressure.
I think the PPU cases are good for 53k psi, but I want the pressure a 30-06 is capable of, or a 270 WIN.

I'm not convinced 7x57mm brass is not good to at least 53k psi. I notice that 6mm Rem is loaded up to 63k psi. Has the 6mm Rem case, based on 7x57mm, been "beefed up" over the parent case? I doubt it. And how would the 6mm be made stronger? Only by reducing internal capacity by making the case walls thicker.

This page (http://www.chuckhawks.com/rifle_case_capacity.htm) lists the case capacities for the two cases as:

6mm Remington (R-P): 54.6 grains
7x57 Mauser (W-W): 55.6 grains

My hunch is if you weighed a few 6mm Rem and 7x57mm cases (preferably from the same manufacturer) you would find little significant difference in weight, certainly nothing that couldn't be attributed to the different neck diameters.

PS

I also notice 6mm Rem is loaded to the same max pressures (63k+ psi, Hodgdon data) as 270 Win, so there is nothing to be gained by forming from 270 or 30-06 vs using 7x57mm brass (assuming 6mm Rem and 7x57mm brass are identical other than the necks, as discussed above.) And, in fact if you form from 270 you will end up with less case capacity, so this becomes an exercise in pushing a rope.

Much ado about nothing. Just use 7x57mm brass, unless you simply cannot find any of acceptable quality.

 

[normmatzen]

Yes, JRS, I did look into the breech pressure limit from the CIP standard and figured the PPU cases are made to that limit.

I had no idea what the American made cases were made for.

Brians356
thank you for the combination of lots of knowledge as well as common sense!

I would like to load to 60k psi or so.

By the way, does 356 refer to a very nice driving car made in the early 60's?