Necking up from 270wsm to 7wsm

[ivo]

I have had a tough time finding 7wsm brass but got a good deal on a pile of 270wsm. I have never necked up before but a read up about it and it doesn't seem too difficult. Lube, lube, lube then run it through the FL sizer right? If anyone has any info or tips, especially calibre specific ones, it would be greatly appreciated.
Thanks in advance,
Ivo

 

[Eagleye]

Be careful with this operation!!! The headspace spec is longer on the 7mmWSM than it is on the 270 or 300 WSM, which means if you just neck up to 7mm, you risk case rupture when you go to use the cases. You must neck those cases out to at least 300, preferaby 325 [8mm] and then neck back down to 7mm so you leave a false "shoulder" for the 270 WSM case to headspace on when you fire it. Regards, Eagleye.

 

[ivo]

Be careful with this operation!!! The headspace spec is longer on the 7mmWSM than it is on the 270 or 300 WSM, which means if you just neck up to 7mm, you risk case rupture when you go to use the cases. You must neck those cases out to at least 300, preferaby 325 [8mm] and then neck back down to 7mm so you leave a false "shoulder" for the 270 WSM case to headspace on when you fire it. Regards, Eagleye.

I didn't realize this could be an issue. A reputable gunsmith on another forum said I could even load up the 270wsm brass and seat a 7mm boattail bullet and just fire them that way to fireform. Is this too risky?

 

['Boo]

I didn't realize this could be an issue. A reputable gunsmith on another forum said I could even load up the 270wsm brass and seat a 7mm boattail bullet and just fire them that way to fireform. Is this too risky?

I would reconsider that "reputable" part.

As Eagleye mentioned the 7mm version of the WSM cartridges is slightly longer - 0.0378" at the shoulder - than the 270 version to prevent someone from inadvertently chambering the bigger cartridge in a 270 WSM rifle. Just loading a 7mm bullet in an otherwise unaltered 270 WSM case could result in dramatic case head separation on the first shot due to the excessive headspace.

Again as mentioned by Eagleye forming a larger false shoulder to control headspace during the initial fire-forming would be safe enough.

 

[Eagleye]

I didn't realize this could be an issue. A reputable gunsmith on another forum said I could even load up the 270wsm brass and seat a 7mm boattail bullet and just fire them that way to fireform. Is this too risky?

Yes, this is too risky!! As 'Boo said, your gunsmith is not on the ball on this one. Eagleye.

 

[ivo]

He isn't my gunsmith but he is reputable, none the less I'll have to go another route with this one because I wouldn't want to risk anything disasterous in any gun, let alone a brand new custom.
Thanks for the info,
Ivo

 

[RojamB21]

buy 7 wsm brass be my plan B

 

[tuffteddyb]

I own a 7wsm and i was told only to buy the 7wsm brass when i bought it.the salesman told the the other wsm brass are different.
if you buying loaded ammo watch out for overpressure on certain brands.caused me a lot of grief!