7mm wsm brass

[Prieto9000]

Can I use .270 WSM or .300 WSM brass to make 7mm WSM by just opening or closing the neck??

 

[Hirschi1]

Yes, just use caution when sizing the 300 wsm brass. The neck thickness might need to be turned. The 270 wsm shoulder might need to be pushed back. Check case length before using either after resizing.

I have only been reloading about 20 years, therefore it might be best to seek other veterans thoughts. I still have lots to learn. Good luck!

 

[JeffVN]

the neck length and base to shoulder height for the WSM brass is all different. I recall that the 7 WSM has the shortest neck and tallest base to shoulder height, but you should verify the dimesnisons.

JeffVN

 

[Varmint Hunter]

No, not really. 7 WSM brass has a longer headspace dimension. This was apparently done to prevent 7 WSM ammo from being accidentally chambered in 300 WSM rifles.

It is possible to neck other WSM brass up or down and to create a false shoulder on the neck so that it may chamber snugly in a 7 WSM chamber. Then you can blow the shoulder forward by fireforming. It's a bit of a PITA but it does work.

 

[Hirschi1]

Did a little research.

300 WSM, 7mm WSM, and 270 WSM are equal in case length and that is 2.100 inches.

Where I see trouble is the shoulder. (Bottom of case head to shoulder measurement).

300 wsm is 1.802

7mm wsm is 1.7018

270 wsm is 1.6634

As you can see the 300 is longest at the shoulder and will need the shoulder bumped back .1002 inches ( 1/10 of an inch). And the neck will need to be turned.

The 270 is the shortest at the shoulder, therefore it will only need to be blown out .0384 of an inch.

To me the 270 wsm looks the best option.

Steve

 

[Hirschi1]

Varmint hunter,
Are you referring to the angle of the shoulder and the length of the shoulder?

 

[Varmint Hunter]

Varmint hunter,
Are you referring to the angle of the shoulder and the length of the shoulder?

I am not an expert on headspace but here is my take on this:

The measurements you listed appear to be the measurement from the case head to the body/shoulder junction which is not the headspace dimension. Interestingly enough, headspace (case head to datum line) is never listed.

Additionally, you listed an incorrect measurement for the 300 WSM which should have been 1.664", the same as the 270 WSM. The 270 WSM & the 300 WSM both are shorter in headspace (and other dimensions) than the 7 WSM. Note, however, that all three cases have the same total length.

IMO, the best solution to the unavailability of 7 WSM brass is to merely chamber or re-chamber to 7-300WSM. This would allow you to simply neck down readily available, high quality 300 WSM brass. Case capacity would only be slightly less than the 7 WSM which some precision shooters believe is an improvement.

 

[Hirschi1]

I did post the wrong shoulder measurement the 300 wsm. If you size a 300 or a 270 case in 7 mm wsm full length die it will push back the angle of the shoulder and size the neck. In theory that should work. The brass will need to be fired formed with a light load or pistol powder and wax. What am I missing?

 

[Prieto9000]

I posted the question because I bought a .270 WSM sako finnlight and really didn´t fell in love with the caliber. It kicks like a mule, and the performance is just a little better than a .270 win. I really like the rifle´s set up and I´m considering the idea of rebarreling it and it has to be a WSM caliber because of the action. I´m a huge 7mm fan and thought: Maybe a 7mm WSM is a good idea but found out 7mm WSM brass is almost impossible to find so if I can resize .270 WSM brass or .300 WSM brass without a lot of trouble it would be awesome, but if I´m getting into neck turning, and all that stuff I prefer to leave it alone and stay with the 270 WSM even though I don´t like it that much.
Maybe a .300 WSM is not bad either, but Kicks even harder and I don't really like .300" calibers.
The 6.5 WSM was another player here, but I´m a little afraid barrel life would be compromised so I decided to stay away from it.

 

[Varmint Hunter]

I did post the wrong shoulder measurement the 300 wsm. If you size a 300 or a 270 case in 7 mm wsm full length die it will push back the angle of the shoulder and size the neck. In theory that should work. The brass will need to be fired formed with a light load or pistol powder and wax. What am I missing?

Considering that the shoulder on the 7 WSM case is farther forward or the case head-to-datum line dimension is longer on the 7 WSM how would you expect the sizer die to "push back the angle of the shoulder " on the already shorter cases?

Modified 270WSM or 300WSM cases that merely have the necks brought into 7mm diameter would have excessive headspace in a 7WSM chamber. This is why it is necessary to create the false shoulder on the neck which when done properly holds the case head against the bolt face for proper fireforming.

Like I said - it's a PITA but it does work.

 

[Varmint Hunter]

I posted the question because I bought a .270 WSM sako finnlight and really didn´t fell in love with the caliber. It kicks like a mule, and the performance is just a little better than a .270 win. I really like the rifle´s set up and I´m considering the idea of rebarreling it and it has to be a WSM caliber because of the action. I´m a huge 7mm fan and thought: Maybe a 7mm WSM is a good idea but found out 7mm WSM brass is almost impossible to find so if I can resize .270 WSM brass or .300 WSM brass without a lot of trouble it would be awesome, but if I´m getting into neck turning, and all that stuff I prefer to leave it alone and stay with the 270 WSM even though I don´t like it that much.
Maybe a .300 WSM is not bad either, but Kicks even harder and I don't really like .300" calibers.
The 6.5 WSM was another player here, but I´m a little afraid barrel life would be compromised so I decided to stay away from it.

If you are rebarreling, and based on your stated preferences, I can't imagine why a 7-300 WSM wouldn't be perfect. A 7 RSAUM "may" work well in a WSM action too. Maybe one of the smiths here could comment on that possibility.

 

[Hirschi1]

Thanks varminthunter, that does make since.

The hydrologic method of forming cases would work, however it would take time and be expensive.

 

[Prieto9000]

If you are rebarreling, and based on your stated preferences, I can't imagine why a 7-300 WSM wouldn't be perfect. A 7 RSAUM "may" work well in a WSM action too. Maybe one of the smiths here could comment on that possibility.

After reading this posts I looked into it and found it´s really easier to make a 7-300 WSM. Midway has the reamer in stock so even that is a piece of cake. Just out of curiosity, what makes the 7-300 WSM better than the original 7WSM?? Someone here said most people think it´s a better cartridge.

 

[Varmint Hunter]

After reading this posts I looked into it and found it´s really easier to make a 7-300 WSM. Midway has the reamer in stock so even that is a piece of cake. Just out of curiosity, what makes the 7-300 WSM better than the original 7WSM?? Someone here said most people think it´s a better cartridge.

Some shooters feel that the case capacity of the 7 WSM is slightly more than is optimal for their needs. This is usually dependent on how bulky your powder charge is and/or how much case room is occupied by the bullet base. Using a faster burning powder may result in a case that has too much empty space for the best consistency. However, the 7 WSM works well with heavy bullets and slow burning powder which easily utilizes all the case capacity.
I have been working up loads with the 175 LRAB and Retumbo. Using this combination, a slightly larger case would be helpful.