7wms from 300 WSM

[Jeff Von Rosenberg]

I have read to form 7wsm from 300 it needs to be turned to the point where the 7 shoulder would be than necked down, than fire formed . What adverse affects would there be to just necking down 300 WSM and fire forming to push shoulder forward( shoulder .030 farther forward on 7wsm) ? Just another dumb question. Any danger or damage to gun. This is mr f class and I can't find brass2 barrels and no brass!!!!!

 

[Erik Cortina]

Neck down, then turn, then fire form. That's the correct sequence.

First you have to make sure you have enough clearance. Necking down will make brass thicker. If your neck is big enough to use no turn brass, I would suggest doing a false shoulder to get consistent fire formed brass. However, I would also highly recommend that you turn the brass.

 

[Jeff Von Rosenberg]

Do I have to turn the brass to where I want the shoulder? Can I you full loads for fire form or close to it . I have 2 new marrels and hate to wear them out fire forming!

 

[Savage99]

Just neck down the 300 WSM in the 7mm WSM FL die so that when you chamber the formed case in the 7mm that you can feel some tension as you close the bolt.

I have made both 7mm WSM's and 270 WSM's out of 300 WSM brass.

No need to turn the necks unless your chamber is very tight.

My rifles are commercial chambers in Kimbers and Winchesters.

 

[Steve Blair]

Just neck down the 300 WSM in the 7mm WSM FL die so that when you chamber the formed case in the 7mm that you can feel some tension as you close the bolt.

I have made both 7mm WSM's and 270 WSM's out of 300 WSM brass.

No need to turn the necks unless your chamber is very tight.

My rifles are commercial chambers in Kimbers and Winchesters.

[br]
I agree with Erik on the turning point. OP stated that it was an F-Class rifle, likely not a commercial chamber. The right thing to do is make a dummy round from necked down brass and measure the neck diameter. Clearance should be .004-.005" diametral. If less, turn appropriately.

 

[Erik Cortina]

Do I have to turn the brass to where I want the shoulder? Can I you full loads for fire form or close to it . I have 2 new marrels and hate to wear them out fire forming!

Turn slightly past of where the new shoulder will be.
I would use a reduced load for fireforming. Another way is to have about .004"-.005" neck tension and jam the bullets hard so they will hold the case head against the bolt face. Work up a reduced load that is accurate in your rifle and shoot at club matches.

 

[jfseaman]

I have read to form 7wsm from 300 it needs to be turned to the point where the 7 shoulder would be than necked down, than fire formed . What adverse affects would there be to just necking down 300 WSM and fire forming to push shoulder forward( shoulder .030 farther forward on 7wsm) ? Just another dumb question. Any danger or damage to gun. This is mr f class and I can't find brass2 barrels and no brass!!!!!

Personally, I would not do it unless I had to but with availability being what it is...

The WSM line uses very thick brass.

Pushing the shoulder .030 forward will result in thinning somewhere. Unless you anneal the shoulder I would worry about it being at the web/body junction.

I would add annealing then run the brass through the 7wsm die leaving a false shoulder. Job done.

 

[langenc]

Not to hijack but what about the other way--7 mm WSM to 300 WSM?? I run em thru the die and that is very easy. Little pressure req.

Are they ready to load as 300 WSM?? or same question for 270 WSM to 300 WSM?

 

[Steve Blair]

Not to hijack but what about the other way--7 mm WSM to 300 WSM?? I run em thru the die and that is very easy. Little pressure req.

Are they ready to load as 300 WSM?? or same question for 270 WSM to 300 WSM?

[br]
I use Norma .270 WSM to make .300 WSM brass, solely for cost reasons. Norma .270 WSM is 2/3 the price of Norma .300 WSM. Go figure. I employ both a 7mm and caliber .30 expander, sometimes losing one or two cases per hundred to splits. Then, run all through the Giraud for uniform shoulder to case mouth distance. Neck turning follows trimming, cutting slightly into the shoulder. Then, tumble in SS pins to remove lubricant, anneal and load. My chamber is Ø.337" neck and requires turning.