Hey folks got a question , I have recently started making 257 weath. mag. brass from Win. 7mm mag brass . One pass through a full length die and the stuff looks great cycles great . My question is should I load and shoot it once for fire forming or can I load it for performance ,accuracy , right away . Thanks

Did the same thing. I just loaded for performance, the fireforming is very minor and IMO, doesn't affect the load.

Check neck thickness; that can potentialy be a problem.

.264 WM brass may be a better option, less working of the brass, but harder to find.

DF

I always annealed before the reforming. It just makes it a little smoother and easier to do the process and keep consistent bullet tension. I would then anneal on every third loading after that. I have loaded lots of 7 mm Mag into 257 and it works well.

I used new brass.

I make .240 Wby cases out of 25-06 brass. With that one, you definitely need new brass. Fired brass is much harder. It takes a lot of effort to swage a belted round from a non belted case, even with new, softer brass. Fired brass makes it almost a no-go...

Sizing 7RM to .257 Wby is a lot easier than forming .240 Wby brass.

DF

I would check for the dreaded doughnut before torching off a hot load. The longer neck of the 257 puts some of the shoulder into the neck and the brass can be thicker in the shoulder area. May not be a problem but worth checking.

Actually, the base of the .257's neck is just about exactly the same distance from the head of the case as the base of the 7mm's neck, so there's no danger of a doughnut when necking 7mm RM down to .257.

I stand corrected. I thought it was the radiused shoulder MOJO that prevented doughnuts. If that link works there was a long thread on this before.


https://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/5416151/Re:_257_Weatherby_Brass_Questi

Couldn't figure out how to link this so on the Campfire, so here is the google link for the old 2011 thread that has lots of good info.

What usually causes doughnuts is necking up, because the top of the shoulder of the "parent" case then becomes the bottom of the neck. Brass in the shoulder is usually thicker, so there's the doughnut.

Necking down usually doesn't cause the same problem, because the resized portion of the neck already started as part of the neck in the parent case.

I can throw away all the bent paper clip feeler gauges now. If you had not called the neck/shoulder junction similarities to my attention I would have kept thinking the 257 was longer or lower, now I need to start micing things instead of eyeballing it. Thanks