Making 257 wby brass from 7mm wby brass

[VinceMule]

Since the headspace is on the belt, I can only guess that there was a LOT of shoulder blown forward. This is somewhat concerning to me since I found that Winchester formed a perfect double radius case. Will be interesting to see if you get any case splits when fire forming...AGD brass is very tough!

Now, you should set the full length sizer to where there is some slight resistance on closing, even though the headspace is on the belt. This gives you double insurance on eliminating case stretch. I fire formed while shooting coyotes coming into the call.

 

[Dean2]

Added back the picture from my post above about necking 460 Bee down to 338-378 Weatherby, that seems to have disappeared for some reason.

 

[DesertBoy]

I am probably just going to pull them and try a different brass manufacturer. I don't want to risk a case splitting.

 

[VinceMule]

Case splitting at the neck poses no danger.

Are those 375 cases you are forming from?

 

[Calvin45]

I've searched and can't find the post I read about this. So can you use 7mm weatherby mag brass and resize it to 257 weatherby mag? I've never tried doing anything like this before hence the question.
I have a rcbs 257 wby mag die set. Would that be sufficient to reform 7mm wby mag brass? Any issues I may run into?

Thanks

Yup. No worries. Brass me be a tad short. Not a big deal. I've formed 257 from 264 win and 7mm rem brass with zero problems.

 

[Hoss50]

Yup. No worries. Brass me be a tad short. Not a big deal. I've formed 257 from 264 win and 7mm rem brass with zero problems.

Same here. I seemed to get about 4-6 firing per case before neck splits or loose primers.

Real 257 brass I have drop Norma doesn't seem to neck split, but the primers still get loose.