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 7x57-.257 Roberts.
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Bernie P.
Junior Member

57 Posts

Posted - Feb 24 2009 :  11:01:05  Show Profile Send Bernie P. a Private Message  Reply with Quote
I've been thinking about getting a rifle for varmint/deer hunting and the.257 Roberts is on my short list.I have quite a few once fired 7x57 cases on hand.Can these be used to load for the .257 Roberts?If so will I need anything other than the dies and case trimmer/gauge to resize?

F. Guffey
Advanced Member

USA
690 Posts

Posted - Feb 25 2009 :  00:52:44  Show Profile  Visit F. Guffey's Homepage Send F. Guffey a Private Message  Reply with Quote
I make 257 Roberts from 30/06 military cases, this method allows me to move the shoulder back rather than fire the cartridge to move the shoulder forward. I have also used the same case to form 6.5/ 257 Roberts (Japanese). 7MMX57MM is a perfect choice, I also form the 7MMX57MM from 30/06 cases.

I purchased a 25/284 barrel last week, before I got out of the building I was informed of every thing I will ever need to know about forming 25/284 using 6.5/284 cases, I ask about there thoughts on using a 6.5/284 case to determine case protrusion and the effect the case will have on head space, not much help but that is what I did, .111, perfect, .004 head space. I use an aluminum can crusher to seat a 6.5 bullet in the case backwards (bullet with the flat end out and flush with the mouth of the 6.5/284 case, flat end out), the case neck with the 6.5 diameter bullet was too large in diameter to seat, again, perfect.



The effect of necking a case neck down .027, from .284 (7MM) to .257 has not been decided yet, some say the case neck gets longer, others say the neck gets thicker, could be both then there are others have a problem with pulling the neck expander ball back through the neck and claim chasing run-out begins, I neck them down and check by chambering, I then seat a bullet to check for clearence between the case neck and chamber. Is it passable to size the neck to 6.5 (with out a bullet) and attempt chambering the case in the 257 Roberts?

Turning the outside of the neck may be required, or the inside of the neck could be reamed as an alternative, I do not have a reamer for everything, before full length sizing I will check the inside neck diameter, it could be convenient to ream first.

Commercial cases are thinner than military cases in the body.

F. Guffey
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F. Guffey
Advanced Member

USA
690 Posts

Posted - Feb 25 2009 :  00:56:22  Show Profile  Visit F. Guffey's Homepage Send F. Guffey a Private Message  Reply with Quote
it is possible,

Sorry about that,

F. Guffey
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dmsbandit
Advanced Member



USA
1788 Posts

Posted - Feb 25 2009 :  06:41:00  Show Profile  Send dmsbandit a Yahoo! Message Send dmsbandit a Private Message  Reply with Quote
If memory serves me correctly, the 257 Roberts was based on a necked down 7MM Muaser. If that is so, I see no reason you couldn't just neck down the 7mm cases and then true up the necks.

I don't drink or smoke, I spend my money on gunpowder and gasoline.
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Bernie P.
Junior Member

57 Posts

Posted - Feb 26 2009 :  10:51:48  Show Profile Send Bernie P. a Private Message  Reply with Quote
The .257 was indeed designed on the 7x57 case.My concern is there might be to much brass to "flow" as Richard Lee puts it in his reloading manual.Skimming through Nosler's manual last night I read how they suggest resizing .280 cases to .280 Ackley dimensions.I think the same approach might work for me.Thanks!
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F. Guffey
Advanced Member

USA
690 Posts

Posted - Feb 27 2009 :  07:14:55  Show Profile  Visit F. Guffey's Homepage Send F. Guffey a Private Message  Reply with Quote

Bernie P.,If Nosler left out the part about neck length and the difference between a standard chamber and an Ackley chamber they wasted a lot of paper printing instructions. When forming cases in the Ackley Improved chamber the neck on the parent case is shorter than the improved version causing the neck to be formed when chambered, the rest of the case is formed when fired, something like 'blowing out', they could even use that term, blowing out but not forward in some case would be more correct.

Reaming an Ackley chamber, the short neck of the parent means the Ackley reamer will not clean-up the parent chamber unless the barrel is set back.

Brass flow, brass stretch, different events, I have no concerns about what may be, I have formed 7.62 NATO (similar to 308 Winchester){37.9 inches of trimming for 100 cases} using 30/06 cases without reaming the neck, commercial ammo case thickness (body) as military wall thickness, neck reaming is not always required when forming and necking down cases, having the tools is as important as knowing how to determin when to use them.

Necking down 7MMX57MM to 257 Roberts or forming 257 Roberts from 30/06 cases goes back to before the Internet, some could say 280 AI fire forming is the same as forming brass in in a die is the same as in the necking down the 7X57 case to 257 Roberts, I would say the two techniques/methods are not related.

F. Guffey
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F. Guffey
Advanced Member

USA
690 Posts

Posted - Feb 27 2009 :  07:39:47  Show Profile  Visit F. Guffey's Homepage Send F. Guffey a Private Message  Reply with Quote
wall thickness (body) on commercial ammo is than the wall thickness of military ammo.

Sorry about that,

F. Guffey
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