If I use Norma brass should I neck up 270wsm brass or neck down 300 wsm brass. Seems like the smallest amount of sizing would be down with the 270 but I am just checking what the hide experts are doing. Thanks guys

Jake

It's hard to believe no one besides Winchester makes 7WSM brass. I just use the Winchester but will be interested at your findings, sorry I can't be more help.

It's generally better to size down. I would get the 300 WSM brass to size to 7WSM to avoid any donuts. I don't blame you for looking, since Win brass honestly sucks in the WSM stuff.

i agree with Chad. it seems to keep brass more concentric to neck down.

Not sure that necking up or down to make 7wsm will work, or at least not easily.
The 7wsm is longer from the base to the datum line and base of the neck than the 270wsm to prevent inadvertently firing the 7wsm out of the 270wsm.

Measurements from base to: bottom of shoulder, and bottom of neck:

270wsm 1.664 1.824

7wsm 1.701 1.856

300wsm 1.664 1.802

Good point, Jeff. There doesn't seem to be but .007" difference. Once you sized 300WSM down, wouldn't it fire form to the 7WSM chamber? I haven't played with the WSM necking up and down, and haven't researched the actual sizes and deminsions.

It probably is possible, but does not seem worth the big hassle. I use the Winchester brass. The only thing I do it is uniform the primer pocket and deburr the inside of the flash hole and it works fine.

Just remember, if you neck down, you will need to neck turn as the necks will be way too thick.

Knowing your chamber specs will help when neck turning.

The best thing for you to do is take the 300 brass and neck it down. Start your die a few turns high and move it down untill the brass barely chambers. This will help form it to your chamber properly. Like usmcj said you may need to outside neck turn or use a inside neck reamer after rezising to get the wall thickness down.

Since the 7 wsm case is a bit bigger if you neck up or down is it correct to say that case capacity will stay the same as the 270 or 300 and thus be less????

I believe when you neck down the 300WSM to a 7-300WSM, you have a little less case capacity to that of a regular 7WSM. But the loads are so close, it's hard to tell.

No cause you will be forming it to your chamber.

i called winchester and hornady and they said you couldnt do it. SO I buy Winny brass and I think now Norma make it dont they??? I know a few makers are doing 300 WSM.

All of teh WSM cases (300, 7mm, 270) are different in capacity and a neck length. I do not recall exactly the numbers, but I know for sure that 270 has the longest neck and smallest capacity. (hence this is the one that is the one of the favorites for F-Class shooters as it has the long neck and the capacity is not teh important factor in velocity for teh 180 Bergers).

With a longer barrel, you get identical velocities out of teh 7 SAUM as the 7WSM. Plus because of its shoulder angle, teh 7SAUM feeds from a magazine easier than the 7WSM. If you want to mag feed these, I suggest a long action to retain maximum case capacity regardless of the case that you are talking about.

Personally, I would look at the 7mm/270WSM if I were not wanting to go from 7mmWSM down to 7 SAUM. Then again, I shoot teh straight 7WSM in two different rifles, and have put at least 4,000 rounds down range in the last two years with that chambering. My KMW is now on its second barrel (1,680 rounds through the first one, and it died in the middle of an F-Clas 1,000 yard relay)

.300 WSM has a touch less in capacity but a slighly longer neck than the 7 WSM. Of the three, the straight 7WSM has teh shortest neck and largest capacity. (again by a small margin on the capacity)

I didn't find teh Whinny brass to be that bad, but I bought aton of it and then prepped it in batches. I still have at least 200-300 sitting in my garage waiting to be prepped.

JeffVN

I wonder when lapua or norma will start making the 7WSM???