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  #1  
Old 01-28-2014, 01:50 AM
orrwdd orrwdd is offline
 
Join Date: Jan 2014
Location: Rigby, Idaho
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Default Criterion 308 Barrel safe with 7.62 NATO rounds

I have ordered a HRA CMP Special Grade with the Criterion 308 barrel. Will the chamber on this barrel be save with 7.62 Nato ammo and brass?

Thanks
Bill
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  #2  
Old 01-28-2014, 03:02 AM
dowell1865 dowell1865 is offline
 
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Location: ky
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Should be a gunsmith can variety . Had a Mauser barreled with a Norwegian match barrel he set it up where I can shoot both safely
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  #3  
Old 01-28-2014, 08:13 AM
normannewguy normannewguy is offline
 
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Ok here it is again.

Saami 308Win:
GO 1.630
NO GO 1.634
FIELD 1.638

FN FAL:
GO 1.6325 (FN & Brit/commonwealth) (Canadian is 1.6315)
NOGO 1.638
FIELD 1.640

7.62NATO (M14 US MILSPEC):
GO 1.6355
NOGO 1.638
FIELD 1.6445


Chamber and cartridge drawings. 308 WIN and 7.62 NATO

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

http://s1052.photobucket.com/user/f6...tml?sort=3&o=3

Both cartridges are the exact same dimesions . The only difference between the two is usally the weight of the brass, NATO weighs in at 175 grains to 188. SAMMI brass is about 155 to 165 grains.
Looking at the go for SAMMI and NATO there is a .005 difference. This will not be a problem in using NATO ammo in a 308 chamber. 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 NATO chamber is fine but is .003 to .005 to large for a Win chamber. Most US ammo companies , Winchester being one, who make NATO ammo go to the minimum spec and hold it there, 1.628 and that allows it to be chambered in both.If you have a minimum chamber 1.630 you can run into feeding problems with some NATO spec ammo but normally only overseas stuff, like PPU.
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  #4  
Old 01-28-2014, 08:37 AM
Paladin601 Paladin601 is offline
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Quote:
Originally Posted by orrwdd View Post
I have ordered a HRA CMP Special Grade with the Criterion 308 barrel. Will the chamber on this barrel be save with 7.62 Nato ammo and brass?

Thanks
Bill
My 308 Garand WILL NOT shoot the 7.62. The bolt will not close on the round. I stick to .308 with. On my 308 bolt gun it chambers with difficulty. I bought some 7.62 thinking it was okay, but will not do that anymore.

Seems to be a 50/50 argument about whether it is the same or not. If it won't close on the 7.62, have a gunsmith check it out a a half turn on the reamer should solve the problem. I wanted a tight 308 chamber on mine.
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  #5  
Old 01-28-2014, 08:57 AM
Parkr1942 Parkr1942 is online now
 
Join Date: Oct 2013
Location: Louisville, Ky
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Why not ask CMP if it is chambered to shoot both? That would seem to be where to start ....and then check the chamber when received to verify what you got and go from there. getting access to "correct" Nato guages is sometimes a problem, but there may be a CMP Member near you who could helo you out on that.....or advise yu on wher to find true Nato Spec guages.

Love to hear what you find out....Good Luck
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  #6  
Old 01-28-2014, 09:03 AM
normannewguy normannewguy is offline
 
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Quote:
Originally Posted by Paladin601 View Post
My 308 Garand WILL NOT shoot the 7.62. The bolt will not close on the round. I stick to .308 with. On my 308 bolt gun it chambers with difficulty. I bought some 7.62 thinking it was okay, but will not do that anymore.

Seems to be a 50/50 argument about whether it is the same or not. If it won't close on the 7.62, have a gunsmith check it out a a half turn on the reamer should solve the problem. I wanted a tight 308 chamber on mine.
Again like I have said multiple times before, there are no differences between the rounds, only chamber headspace and a small amount of freebore area. The main problem being foreign ammo companies use NATO specs so if it comes out to 1.634 that's ok because it will still chamber in NATO chamber but have difficulty in SAMMI. Tight chambers in 308 do not always increase accuracy. The match teams of the US Army and USMC found that a chamber of 1.633 headspace worked the best for match shooting. That is why LRB sends their finished rifles out with that headspace.
So look at the cartridge drawings and the two differences are headspace allowed 1.628 - 1.634 for NATO and 1.627 - 1.634 for SAMMI and a .001 difference in basic area ( stronger webbing in case are for NATO) but overall length are the same. There are no differences between the two nor is pressure radically different. If you can read a machinist drawing you will see that.
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  #7  
Old 01-28-2014, 09:08 AM
Paladin601 Paladin601 is offline
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Quote:
Originally Posted by normannewguy View Post
Again like I have said multiple times before, there are no differences between the rounds, only chamber headspace and a small amount of freebore area. The main problem being foreign ammo companies use NATO specs so if it comes out to 1.634 that's ok because it will still chamber in NATO chamber but have difficulty in SAMMI. Tight chambers in 308 do not always increase accuracy. The match teams of the US Army and USMC found that a chamber of 1.633 headspace worked the best for match shooting. That is why LRB sends their finished rifles out with that headspace.
So look at the cartridge drawings and the two differences are headspace allowed 1.628 - 1.634 for NATO and 1.627 - 1.634 for SAMMI and a .001 difference in basic area ( stronger webbing in case are for NATO) but overall length are the same. There are no differences between the two nor is pressure radically different. If you can read a machinist drawing you will see that.
I agree to disagree, I am not going to argue the point when authors have it in print that they are not the same.

I should mention that the 7.62 I tried were American Eagle. I don't know if that makes a different.

Last edited by Paladin601; 01-28-2014 at 09:33 AM. Reason: added text
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  #8  
Old 01-28-2014, 09:12 AM
Duce Duce is offline
 
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Have shot 7.62 NATO-spec rounds from two different manufacturers through my Criterion .308 barrel (LC, FNM) as well as non-NATO-spec 7.62 (R1M1, POF) with no problems.
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  #9  
Old 01-28-2014, 09:32 AM
normannewguy normannewguy is offline
 
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Quote:
Originally Posted by Paladin601 View Post
I agree to disagree, I am not going to argue the point when authors have it in print that they are not the same.
REALLY? Who are these authors and please direct me to their articles and what are the differences they point out?
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  #10  
Old 01-28-2014, 09:42 AM
Paladin601 Paladin601 is offline
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Quote:
Originally Posted by normannewguy View Post
REALLY? Who are these authors and please direct me to their articles and what are the differences they point out?
Clint McGee on building a Garand and Jerry Knudhausen on the Garand / M14 shop manual. You can read it, I am not going to type out the text.

Also, they make 7.62 reamers, gages, and die, as I have said before. If they were the same don't you think they wouldn't make separate equipement.

We had done thins before, there will not be a different outcome, why not go over the last thread you wanted to argue about the same subject.
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