Necking up or down??

[ishootkittens]

I am trying to start reloading for a 7 wsm and sometimes the brass is a little hard to come by so I was wondering which would be easier and more efficient...necking down a 300wsm or necking up a 270wsm brass? And if its not to much trouble. Could someone justify why they would choose necking up over necking down.. or vice versa... THANK YOU!

 

[boomtube]

Necking down tends to produce better necks.

Factory necks are already too thin to give a good chamber fit.

Case are not suppported when pushing in an expander so the necks stretch to the thin/soft side. Necks are supported squeezing them down; that helps concentricity of the fininished necks.

 

[gr8whyt]

Necking up has a risk. The head stamp would show .270 WSM. If someone picks up one of your 7 WSM rounds and it says .270 WSM on the head stamp, that person might think it's ok to shoot it in their .270 WSM rifle. It will probably chamber. It probably won't have much clearance for proper bullet release (high pressure). And the bullet is .284 going down a .277 bore (very high pressure). Just something to be aware of.

-- gr8whyt

 

[MontanaRifleman]

In the case of the WSMs, if you neck up or down to a 7mm you will have to fireform because the 7mm WSM is about .050 longer at the shoulder than the 300 or 270.

I agree with others... necking down is better so you don't stretch your necks too thin.

 

[mountainman]

I've never necked anything up, but I do neckdown 8mm mag brass to 7mm stw and 30.06 to 270. You do need to fireform the cases but do it with a reduced load to keep from over stretching or spliting the necks and to get the right dimensions. If someone gets ahold of my ammo and uses it a 8 mag or 30.06 and it chambers , then they shouldn't have any problems other then poor accuracy and split necks. After downsizing check your oal of your cases before loading, trim if needed. I turn my case necks also to get the thickness down and even if needed. I've also been pondering if I should anneal the cases because I've overworked the brass, still kicking that idea around.

 

[ishootkittens]

sooooo.... i should basically just order some 7wsm brass from the internet and ask no more questions lol

Could someone explain fireforming to me in a nutshell. I have read some about it and everyone keeps throwing around that term.. but im actually still in the learning stage.

 

[mountainman]

If you were to size down the 300 case to the 7mm case like your asking about it will not have the exact shape of the factory 7mm case but it will chamber. so fireforming( shootform) the case by chambering the sized down, neckeddown case and shoot it to form it to the chamber and factory case shape. If you size a 300 case down to 7mm and compair it to the factory 7mm case you will see what I'm talking about. The cases wont be the same shape but very close, when you fireform or shootform the cases will be the same shape. It's really nothing more then shapeing the shoulder and squaring out the corners. It's very safe and easy to do, use a reduced load to make it easier on your brass and extend the brass life. After fireforming just check the brass lenght and trim if needed.

 

[ishootkittens]

sweet thanks man. I appreciate that! Ill try to get 7 brass, but if I have to get 300wsm brass then I will probably look to you for more info on the subject. But atleast I understand it now. Thank you again.

 

[mountainman]

Your welcome, I will say though that when I fireform I go as cheap as I can. It's a load I'm not going to use for anything, thats just me. I wont use lead bullets other then in my sharps, just jacketed bullets, the cheapest I can find in any weight, the cheapest primers, not BR's, what ever powder that will allow me use the least amount on a midrange load, I wont even waste a target, I'll shoot in the river, a stick, rock, whatever, I just waste a round to fireform and wake the neighborhood.

 

[etisll40]

Can you give an example about fireforming?

What would the minimum amount of powder to use?

Cheap copper bullets right?

or how about oatmeal?

what are the cheapest primers?

Odd question- Will 8mm brass necked down to 7mm stw be better to use in the long run?

Long run being accuracy and case life?

Thanks

 

[Bart B]

Factory necks are already too thin to give a good chamber fit.

Why are they too thin?

As long as the case neck's well centered in the chamber neck, what difference does it make?

I ask this 'cause some folks using WCC58 .308 Win. match brass full length resized in standard SAAMI dimension chamber having several thousandths clearance around the case neck to chamber wall easily shoot sub half-MOA at 600 yards. They've got the thinnist factory neck wall thickness of any I know of. With the case weighing only about 150 grains, that's normal.