.264 or 7mm Brass for .257 Roy?

[Hondo64d]

I'm going to use either 7mm Rem Mag or .264 Win Mag brass for my .257 Weatherby, and was wondering which one would be preferable.

I've read that either work, but the necks are a little shorter than Weatherby brass. Which one would result in the longest neck? Seems to me that the 7mm probably would, but I don't know if that is necessarily the case.

Another concern is case loss during the initial sizing. When I was running a 25-284, until I started using the seating die (conventional design) as an intermediate step, I was loosing probably 50% of the cases when going from 284 case to 25-284 case. I would like to use my seater as an intermediate sizing step with 7mm brass (if I decide to go with 7mm brass) but now I use Forster's straight line seating dies and don't know if they will support being used in such a manner. If I use .264 brass, I am pretty sure that no intermediate step will be needed.

I guess the only possible advantage to using 7mm brass might be a slightly longer neck, but I don't even know if this is the actual case. Has anyone tried both?

Thanks,

John

 

[Long Time Long Ranger]

I have used both for the 257, 270 and 7mm wbys. In your application if I had a choice I would use the 264 winchester brass. The extra length gained with the 7mm would be minimal and the 257 stretches cases so fast it will be at the proper length in no time. 264 to 257 is really easy.

 

[Hondo64d]

Thanks for the reply. Got a bag of Winchester 7 mag brass to try. Better availability. Since I have to size it anyway, it doesn't really matter, but the case necks were in the worst condition of any brass I have ever seen. Probably 30% significantly dented. Anyone else seen this with Winchester brass?

John

 

[LRSickle]

I've use 7mm brass for my 257wby all the time. I just run it through my regular dies with no intermediate steps.
I not sure what Hondo64d is doing different but I bought four bags of fifty Winchester brass last month and I only had one that I had to throw away. I had no hydraulic dents at all.
The finished brass is shorter than the 257Wby brass but I notice no difference in accuracy or pressures.

 

[Hondo64d]

Not doing anything different at this point, 'cause I haven't even sized any yet. I was commenting on the conditions of the case mouths of the Winchester virgin brass I bought.

John

 

[340Shooter]

On the subject of Winchester brass. I got some in .458, and they were dented at the case mouth also. Pretty crappy quality control!