I should be able to make 257 weather mag from 7mm rem mag without any problems shouldnt i . thanks in advaance

Ho You can run a 7mm Rem case through your 257 Wby FL size die and you will reform the case enough to chamber that case. When you load and fire that case the shoulder will fireform to a perfectly shaped 257 case. However depending on what make of brass you use it will NOT have quite the capacity of the Wby brass. So a load that is max in a Wby case will have excessive pressure in your formed case. As a approximation weigh your cases and for every 10 grs your formed case is heavier than the factory Wby case your max load will be reduced by 1 gr of powder. That usually ends up being 2 to 3 grs

I have no problems necking up cases (like 7mm or .30 RUM up to .375 RUM, or 7 STW to .300 Wby), but every time I try necking down a case (like 7mm down to .257) I get dimples in the shoulders.

snowman thanks for the advice.

quote:

Originally posted by buffybr:
I have no problems necking up cases (like 7mm or .30 RUM up to .375 RUM, or 7 STW to .300 Wby), but every time I try necking down a case (like 7mm down to .257) I get dimples in the shoulders.

It all depends on how much reduction, or expansion, you wish to get.

We neck up and down in quite large size.

The secret is you need to do all that in stages.

We make our own expansion rods and necking down buttons.

You can also purchase these from various manufacturers.

Before we started making our own, we used to get them from Neil Jones.

He made excellent dies for forming.

Can you not find 257 brass, or just trying to save money?

theback40 I couldnt find any when i first got the gun but a did run into some factory loads a couple days ago . So im in pretty good shape now

I looked, and found I have some new brass from when I had one.

back40 sent you a message

There is .264 WM brass for sale in the classified section---they would make things a bit easier as necking down very little then simply fireforming.

Hip