300 w mag brass to 7mm mag

[Steve Ladino]

I have the opportunity to get some once fired 300 w mag brass ...was wondering if just resizing it in a 7 mm mag F L die will do the job plus some neck turning maybe ??? ~ Steve

 

[sbhooper]

I think that you can. It seems to me that a long time ago, I did that with some, but we will see what others say.

 

[AndyA]

I had a 300 wm mixed in with some 7rm brass and it wouldn't go thru the die. Shoulder is too far forward. You would be making 7-300 win mag brass.

 

[shoot4fun]

Agree with AndyA.
I wouldn't try it.

 

[Bart B.]

I and others have sized 300 Win Mag brass in 30-338 Win Mag full length dies setting the shoulder back about 1/10th inch making 30-338 Keele Mag cases. Shoulder and body dimensions are the same but longer neck on the
Keele version.

With the right lube and clean cases operating the press slow, one can make 7 Rem Mag cases from 300 Win Mag cases, they'll need trimming. A 338 Win Mag intermediate die may be needed to size necks in two steps.

 

[Steve Ladino]

I and others have sized 300 Win Mag brass in 30-338 Win Mag full length dies setting the shoulder back about 1/10th inch making 30-338 Keele Mag cases. Shoulder and body dimensions are the same but longer neck on the
Keele version.

With the right lube and clean cases operating the press slow, one can make 7 Rem Mag cases from 300 Win Mag cases, they'll need trimming. A 338 Win Mag intermediate die may be needed to size necks in two steps.

Hadn't thought about the big difference in neck OD's....Thankyou.

 

[cowboybart]

You'll have to push the shoulder back to make 7 mag.

If you need 7 mag brass I have some - and I have a buddy that can use the 300 WM brass.

 

[Zero333]

Anneal the brass before doing any sizing. It makes the sizing much easier.

 

[ireload2]

You just lube the brass and mash it with a good press. Be sure to size it so it headspaces on the shoulder.

The suggested use of a .338 die or a .308-.338 die as an intermediate step is very good.
If you can size the cases without annealing that is good. Anneal after forming.
It is possible that too much annealing before sizing will leave the cases so soft they will collapse when formed.

 

[Steve Ladino]

You'll have to push the shoulder back to make 7 mag.

If you need 7 mag brass I have some - and I have a buddy that can use the 300 WM brass.

You just lube the brass and mash it with a good press. Be sure to size it so it headspaces on the shoulder.

The suggested use of a .338 die or a .308-.338 die as an intermediate step is very good.
If you can size the cases without annealing that is good. Anneal after forming.
It is possible that too much annealing before sizing will leave the cases so soft they will collapse when formed.

Because of my enthusiasm to obtain the 300 brass ($6.00 a box) I hurried past looking at the dimensional differences of the two in my Sierra manual. I now see that besides the neck differences there are longitudinal differences too so I have tabled the idea of forming to 7 mm mag brass. Thanks for all of your input ~ Steve

 

[MagnumManiac]

One word of warning. I made several hundred 300WM cases into 270 Weatherby cases, the forming was easy enough with a few steps, BUT the necks get very thick, as the neck is being formed by a part of the case that is the shoulder in the 300WM brass.
You will most likely need to turn the necks after forming.

I turn then trim to length, if you size them after trimming, the necks will elongate unevenly I found.

Cheers.

 

[oldroper]

I have the opportunity to get some once fired 300 w mag brass ...was wondering if just resizing it in a 7 mm mag F L die will do the job plus some neck turning maybe ??? ~ Steve

You can take Redding 30-338mag body die and size down 300mag case, trim neck to length then size in 7mag die. You may or may not have to turn necks. I shoot 30-338mag so I can make cases from 300mag and difference on neck thickness was only .015" to .0165" on new necks. You really don't have much of the old necks left. I've never done it with once fired brass or anneal before.

 

[Shrek]

Rechamber to 7mm STW

 

[Magic stick]

Because of my enthusiasm to obtain the 300 brass ($6.00 a box) I hurried past looking at the dimensional differences of the two in my Sierra manual. I now see that besides the neck differences there are longitudinal differences too so I have tabled the idea of forming to 7 mm mag brass. Thanks for all of your input ~ Steve

I'm gona do it because I'm cheap and have gotten good result with 308 to 6.5 and 243 cases ,30 06 to 6.5 swede and I'll let you know how it goes