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Forming 257 Weatherby from 7mm mag
- Thread starter slammedsi
- Start date
257 Weatherby from 7 remington mag? It can not be done. The 7 remington mag is too short from the case head to the shoulder and too short from the end of the neck to the case head.
The 300 H&H is a choice.
http://www.rcbs.com/downloads/2010_SpecialOrder.pdf
Page 8 bottom right column part number 38115.
I have short forming dies, short forming dies save me money, set 38115 cost $250.00.
F. Guffey
The 300 H&H is a choice.
http://www.rcbs.com/downloads/2010_SpecialOrder.pdf
Page 8 bottom right column part number 38115.
I have short forming dies, short forming dies save me money, set 38115 cost $250.00.
F. Guffey
People have been using 7mm Remington mag brass to form 257 Weatherby for many years now. I went ahead and gave it a shot this afternoon. I used 20, new Winchester brass. The new brass looks great in every way. Case neck is .05 shorter then standard trim to length Weatherby/Norma brass, but from what I have read this is normal and just fine to use. I went ahead and made a dummy round and cycled it through the gun. Rounds cycle flawlessly! I believe I might have found a good alternative to the expensive Weatherby/Norma cases.
Chaz,
While I was researching this I noticed that everyone was saying use NEW brass, not range/once fired. There wasnt anything saying why you needed to. This first batch I used new Winchester brass. Lubbed five of them up with hornady one shot, Then slowly and smoothly run them through the 257 Weatherby full length sizing die. I was shocked at how easy they form from a 7mm to the 257. The new cases come out looking great, but are 0.05 short in the neck. Everything I read says this is ok. You will have to finish the process with fire forming, but from what I have been reading you can use your standard load you use now. Just to be safe I'm going to use a case of trail boss and the cheapest bullet I can find to start off. I did make a dummy round lastnight and ran it through the gun a few times. It cycles great, the bolt opens and closes smoothly, and has no problems chambering the round. I plan on posting some photos once I get a batch fire formed.
While I was researching this I noticed that everyone was saying use NEW brass, not range/once fired. There wasnt anything saying why you needed to. This first batch I used new Winchester brass. Lubbed five of them up with hornady one shot, Then slowly and smoothly run them through the 257 Weatherby full length sizing die. I was shocked at how easy they form from a 7mm to the 257. The new cases come out looking great, but are 0.05 short in the neck. Everything I read says this is ok. You will have to finish the process with fire forming, but from what I have been reading you can use your standard load you use now. Just to be safe I'm going to use a case of trail boss and the cheapest bullet I can find to start off. I did make a dummy round lastnight and ran it through the gun a few times. It cycles great, the bolt opens and closes smoothly, and has no problems chambering the round. I plan on posting some photos once I get a batch fire formed.
myfriendis410
New member
I had been told sometime in the past that the 7mm r.m. was the parent case for the .257 wby mag. How did the double rounded shoulder look? I would expect fireforming to be necessary to blow those curves out. Look forward to seeing your pictures.
375 H&H was the starting case for the .257. The 300 H&H I believe was used for all the other Weatherby's. When setting a normal Weatherby brass next to one that was formed from the 7mm, the 7mm looks and measures correct. From what I understand, Fire forming is a must but they sure dont look like they need it to me.
fantastic, I have forming dies, my favorite forming dies are short.
As has been mentioned when forming Weatherby cases the shoulder of the Weatherby has a radius, forming a radius has not worked for me. Seems the radiys of the full length sizing die at the shoulder causes the case to continue making the turn at the shoulder/neck juncture, and the 7mm Remington Mag is .060" shorter than the 257 Weatherby.
"I believe I might have found a good alternative to the expensive Weatherby/Norma cases"
Because of forming mag cases for wildcats I am short on cases, again, because of the length of the 7mm Remington mag case there is not enough increase in case length when forming when necking up, there could be when necked down.
F. Guffey
As has been mentioned when forming Weatherby cases the shoulder of the Weatherby has a radius, forming a radius has not worked for me. Seems the radiys of the full length sizing die at the shoulder causes the case to continue making the turn at the shoulder/neck juncture, and the 7mm Remington Mag is .060" shorter than the 257 Weatherby.
"I believe I might have found a good alternative to the expensive Weatherby/Norma cases"
Because of forming mag cases for wildcats I am short on cases, again, because of the length of the 7mm Remington mag case there is not enough increase in case length when forming when necking up, there could be when necked down.
F. Guffey
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While I was researching this I noticed that everyone was saying use NEW brass, not range/once fired. There wasnt anything saying why you needed to.
Wander why that is? I have some new and used 7mm. When I have some time I will try both and see what happens. If I ran the fired 7mm through a FL 7mm die first I can not think of what the practical difference would be.
EDIT: I think as long as neck tension is good I could make up the .05 or .06 difference by not seating quite as deep.
Chaz, in the manufacturing of a brass case it is necessary to anneal it as many as 6 times. Firing a case hammers the case from the inside out, hammering a case works the case. the old stand-by answer 'all you gotta do is...', is not a good response.
Stress is created when forming, a good start would be to anneal before forming, split necks are a guarantee when using fired cases that have not been annealed. I am not the fan of building up a stock pile of loaded ammo. If I form without annealing I can expect necks of loaded ammo to split, time? Within a year, maybe 2.
F. Guffey
Stress is created when forming, a good start would be to anneal before forming, split necks are a guarantee when using fired cases that have not been annealed. I am not the fan of building up a stock pile of loaded ammo. If I form without annealing I can expect necks of loaded ammo to split, time? Within a year, maybe 2.
F. Guffey
I've shot 5 to 10 year old reloads whose cases were never annealed in the dozen or more shoot/reload cycles they went through and no split necks at all. Maybe that's due to the loaded rounds being stored bullet down and the powder gently pressing on the bullet-neck juncture kept the brass soft and supple in that dark, close intimate relationship they had together.
They shot as good as if new.
They shot as good as if new.
reynolds357
New member
I have re-loaded stuff sitting around from the 70's that was not annealed.
slammedsi, 257Wby,270Wby and 7Wby are same case length. It's pretty easy form 7mag case to those using a new case.
Only problem is trim length and you should use max for the 7mag case that's 2.500". I know some that let it get too long then split necks.
I've got plenty of 270Wby brass but took a few 7mag case just to see what they look like formed.
Well good luck
Only problem is trim length and you should use max for the 7mag case that's 2.500". I know some that let it get too long then split necks.
I've got plenty of 270Wby brass but took a few 7mag case just to see what they look like formed.
Well good luck
Bart B., I know, you have fired cases 47 times with max loads, you seem to have an exemption.
This thread started with forming, then someone ask about using new cases, I suggest annealing in the absence of new cases. I have formed thousands of 7mm57 cases from 30/06 cases. When fired in military chambers the formed 7mm57 case necks get a work out.
I have a few friends that decided to ream 7mm57 chambers to 280 Remington, it worked but the chambers had necks with two different diameters because the 280 Remington reamer will not clean all of the 7mm57 chamber because of the large necks.
F. Guffey
This thread started with forming, then someone ask about using new cases, I suggest annealing in the absence of new cases. I have formed thousands of 7mm57 cases from 30/06 cases. When fired in military chambers the formed 7mm57 case necks get a work out.
I have a few friends that decided to ream 7mm57 chambers to 280 Remington, it worked but the chambers had necks with two different diameters because the 280 Remington reamer will not clean all of the 7mm57 chamber because of the large necks.
F. Guffey
Chaz, in the manufacturing of a brass case it is necessary to anneal it as many as 6 times.
Yep, that was probably the practical difference I was not thinking of. Might have to pull out my tempering oven and dust it off.
Peter M. Eick
New member
I know the first time I picked up a 257 weatherby brass at the range and flipped it over to see the headstamp say 7mm Rem Mag I was quite surprised. This is one of the reasons I am looking at switching one of my 25/06's (Ruger #1) to 257 Weatherby. The ease of converting 7mm Rem Mag into 257 W.
Might have to pull out my tempering oven and dust it off.
You'll wreck your cases if you do this. Google "annealing rifle brass", there is a lot of information out there on how to do this properly (and a lot showing improper techniques). You don't want to anneal the case head or body, just the neck.
You'll wreck your cases if you do this. Google "annealing rifle brass", there is a lot of information out there on how to do this properly (and a lot showing improper techniques). You don't want to anneal the case head or body, just the neck.
Not a problem. I can set it up to anneal any part of the case I want.
reynolds357
New member
Just a tad bit easier to make them from .264 Win mag. than to make them from 7 Rem mag. The .26 to .25 neck down is almost not even noticeable its so easy. To be done right, it should be fire formed.
Stress is created when forming, a good start would be to anneal before forming, split necks are a guarantee when using fired cases that have not been annealed.
257 Wby seems to be an especially bad culprit in this regard. I have found that original 257 cases will split on their 3rd or 4th trip into the sizer if they aren't annealed first.
I formed a batch of 7mm mag cases into 257 and loaded them with the lowest listed load for H4831 to fireform them. I lost about 30% with split necks on initial firing. I annealed the next batch I did before necking them down and lost none.
It has become my normal practice to anneal all on my 257 brass after every firing. It is the only caliber I feel the need to treat this way. The 257 Weatherby is it's own unique animal.