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Old 09-03-2014, 07:24 PM
normannewguy normannewguy is offline
 
Join Date: Dec 2009
Posts: 899
Default Cartridge & Headspace Specifications: .308 Win / 7.62 NATO

Ok, here are the specs again...

SAAMI .308 Winchester:
GO: 1.630 in.
NO-GO: 1.634 in.
FIELD: 1.638 in.


FN FAL:
GO: 1.6325 in. (FN & Brit/commonwealth. Canadian is 1.6315 in.)
NO-GO: 1.638 in.
FIELD: 1.640 in.


7.62 NATO (M14 US MILSPEC):
GO: 1.6355 in.
NO-GO: 1.638 in.
FIELD: 1.6445 in.


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Chamber and cartridge drawings...

1. .308 Winchester:
Direct link: http://s1052.photobucket.com/user/f6...tml?sort=3&o=2





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2. 7.62 NATO:
Direct link: http://s1052.photobucket.com/user/f6...tml?sort=3&o=3





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Both cartridges have the exact same external dimensions! The only difference between the two is usually the weight of the brass (generally due to thicker brass near base on NATO cartridge)...
- .308 Win SAAMI brass weighs in average between 155 - 165 grains.
- 7.62 NATO brass weighs in average between 175 - 188 grains.

Looking at the GO for SAAMI and NATO there is a .005 difference, which means there will not be a problem in using 7.62 NATO ammo in a .308 chamber.
Most US ammo companies who make NATO ammo (Winchester being one) produce to the minimum spec of 1.628 and hold it there, which allows it to be chambered in both.

The only time you run into a problem is overseas ammo companies who make ammo to NATO standards. They will let stuff go that headspaces at 1.633 to 1.635 which in a 7.62 NATO chamber is fine, but is .003 to .005 too large for a .308 Win chamber.

If you have a minimum chamber of 1.630, you can run into feeding problems with some NATO spec ammo but normally only overseas stuff, like PPU
.

Last edited by Big_Red; 12-27-2014 at 02:23 AM. Reason: Nit-picking / clarification
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