neck diameter

[canuck]

I really don't know much about guns/chambers so this might be a stupid question to those in the know..
Why aren't all the neck diameter,sammi) specs the same on 7mm cartridges?
I am having some guns built so hope I didn't screw up here.
I ordered a 7mm saum reamer with a .314 neck
I also ordered 7mm rm and stw reamers with .315 necks

Are these going to be ok?

, I have a sinclair neck turning tool so I figured I would get away with a light turn just to clean up the brass a bit)

 

[CJ6]

Seat a bullet that you plan on useing in each case. Measure the outside diameter,add .0025-.003.That shold be your Reamer neck diameter.

 

[canuck]

I did do that and they all measured around 0.310 I just started having second thoughts when I saw how much bigger the sammi specs were.Thanks

 

[Cheechako]

canuk

Don't forget, SAAMI specs are minimum chamber. You may find factory chambers larger than that. That's why we have custom barrels and chambers.

The specs differ between cartridges because the cases used to establish the spec have different neck wall thickness.

Ray

 

[canuck]

Thanks for the input...much appreciated....i feel better now..

 

[Preacher]

canuck--
with a .314 neck on a 7mm saum you'll be doing more than a cleanup cut on the brass if your using Remington brass..
The reamer for my improved 7mmsaum has a .316 neck and the brass is close to .016 uncut and needs to be cut at .013.8 for that perfect fit to the chamber..

 

[jamesh]

canuck,
As Preacher said you will be doing a lot of turning on the 7mm SAUM if you have a .314 neck. Un-turned necked down Nosler 300 SAUM measures .316" with a 162 Amax seated. Un-turned necked down Norma 300 SAUM measures .316" to .317" with a 162 Amax seated.
My no-turn reamer for necked down Nosler 300 SAUM to 7mm has a .318" neck, it works great.

James