The Firing Line Forums

Go Back   The Firing Line Forums > The Hide > The Art of the Rifle: General

Reply
 
Thread Tools
Old November 26, 2011, 08:23 AM   #1
TNT
Senior Member
 
Join Date: June 4, 2006
Location: Back in glorious Nebraska
Posts: 606
.308, 7.62, 7.62 NATO and .223, 5.56 differences R.I.P.

I just thought I would post this response from Hornady, I asked them what the differences were from the professionals who would know. Not that I have a .308 but others might. I did know there was a shoulder differences in both. But as in what role it played I was not quite sure. I did allot of reading both in books and internet on this trying to find the right answer so finally I just sent them a email and the next day I got a answer from them. here is what they sent me as a reply. (I did talk to him over the phone as well)

"Tomas, the chambers are different in these firearms. The NATO chambers have much longer throats.
You can fire the 308 Win and 7.62 in a 7.62 NATO chamber but you cannot fire a 7.62 NATO round in a 308 Win chamber.

This is the same for the 223 Rem. verses 5.56.

I tried to call you this morning but you must have been at work. If you have any other questions you are welcome to call me at 1-800-338-3220 so I can explain it better for you.

Thank you"
__________________
"In the beginning of a change, the patriot is a scarce man and brave, hated and scorned. When his cause succeeds, however, the timid join him, for then it costs nothing to be a patriot."
TNT is offline  
Old November 26, 2011, 08:41 AM   #2
madcratebuilder
Senior Member
 
Join Date: November 2, 2007
Location: Northern Orygun
Posts: 4,868
That is wrong.

5.56 in a .223 may have a leade issue.

.308 vs 7.62 is head space requirement.
madcratebuilder is offline  
Old November 26, 2011, 08:53 AM   #3
TNT
Senior Member
 
Join Date: June 4, 2006
Location: Back in glorious Nebraska
Posts: 606
This is what they told me I have heard many things but never a definitive answer. I know people have taken the .223 and 5.56 and some have taken the .308 and 7.62 NATO and interchanged them some with no ill effects. And it is entirely possible that this guy may have the right results for the wrong reasons. I just thought I would pass this along. Every rifle is different so it will respond differently as well.
__________________
"In the beginning of a change, the patriot is a scarce man and brave, hated and scorned. When his cause succeeds, however, the timid join him, for then it costs nothing to be a patriot."
TNT is offline  
Old November 26, 2011, 09:09 AM   #4
jonnyc
Senior Member
 
Join Date: July 20, 2009
Location: PA
Posts: 825
"the chambers are different in these firearms"

If he stopped there he would have been fine. Beyond that he's been reading too much internet myth.
The belief that they're two different rounds might be dead, but he sure didn't kill it.
jonnyc is offline  
Old November 26, 2011, 09:33 AM   #5
Art Eatman
Staff Lead
 
Join Date: November 13, 1998
Location: Terlingua, TX, USA
Posts: 22,540
"The NATO chambers have much longer throats." Yup. The leade is longer in the front of the NATO chamber. I don't think I'd use the word "much", however.

it will only make a difference if the NATO bullet protrudes farther from the case neck than the equivalent civilian load and the ogive of the bullet is very close to or touches the entry of the rifling.

It's mainly a potential problem with the .223. I've never seen it matter in the thirty caliber. If you want to shoot 5.56 in a .223 rifle, merely ream a smidgen at the front of the chamber.

In thirteen years at this website and with THR since its inception, I've not read of any eye-witness account of somebody having a problem with shooting a 5.56 round in a .223 chamber.
__________________
You're from BATFE? Come right in! I use all your fine products!
Art Eatman is offline  
Old November 26, 2011, 05:06 PM   #6
TNT
Senior Member
 
Join Date: June 4, 2006
Location: Back in glorious Nebraska
Posts: 606
maybe what he said was just a legal disclaimer
__________________
"In the beginning of a change, the patriot is a scarce man and brave, hated and scorned. When his cause succeeds, however, the timid join him, for then it costs nothing to be a patriot."
TNT is offline  
Old November 26, 2011, 05:36 PM   #7
Ridge_Runner_5
Senior Member
 
Join Date: February 8, 2008
Location: Denver, CO
Posts: 1,882
Quote:
It's mainly a potential problem with the .223. I've never seen it matter in the thirty caliber.
I had a Remington 770 in .308 Win that took a helluva lot of force to remove a 7.62x51 casing once fired.
Ridge_Runner_5 is offline  
Old November 26, 2011, 08:25 PM   #8
jukk0u
Junior Member
 
Join Date: October 26, 2011
Location: Kirkland WA
Posts: 5
7.62 military/NATO vs. .308 in the M1A

Springfield claims that only 7.62 NATO/Military ammunition (factory) should be fired in the M1A.
They do not mention head spacing or other issues of measurement but instead refer to the PRIMERS.
They insist that the military primers are harder and resist primer detonation caused by the firing pin which slightly (or more) impacts the primer when the bolt slams forward. (slam fire)

Interestingly the factory manual does not address bullet weight. (which, at heavier weights might affect head space?)
__________________
Jukk0u
jukk0u is offline  
Old November 26, 2011, 08:32 PM   #9
Jim Watson
Senior Member
 
Join Date: October 25, 2001
Location: Alabama
Posts: 11,090
Agree with Art, the main thing is that military chambers are cut a bit large in one or another dimension because:
1. They will likely be shot hot and dirty.
2. They may be shot with weird ammo from our alleged allies.
3. The Army doesn't reload.

As to primers, I have seen reliable reports of slamfires with unsecured military firing pins.
I wonder how in the world they were able to make Springfields and Garands that would shoot regular .30-06 just fine. (Absent the present worry about somebody loading .30-06 with 4350 or similar and running up the port pressure on an M1.)
Jim Watson is offline  
Old November 26, 2011, 08:34 PM   #10
bedlamite
Senior Member
 
Join Date: August 10, 2000
Location: WI
Posts: 1,035
http://www.thegunzone.com/30cal.html
http://www.thegunzone.com/556v223.html
__________________
A plan is just a list of things that doesn't happen.
bedlamite is offline  
Old November 26, 2011, 08:39 PM   #11
blacksky
Senior Member
 
Join Date: November 21, 2008
Location: OH
Posts: 738
The Truth About 7.62x51mm NATO and 308 Winchester

Chamber Size:

Look at the table below. The right column represents a military headspace gauge specification; the left one, the SAAMI specification. With many military rifles, the chambers can be significantly longer than, say, a Remington 700. Note that the military chamber would fail a NO GO check with a SAAMI gauge, but pass a FIELD check using the proper military gauges.

There is a .013" difference in acceptability, between these two specifications. This is significant in that, for reloading purposes, brass will stretch more in a military chamber upon firing, thereby reducing the life
of the brass and possibly promoting case head separation. But that additional length will allow a round to chamber in an incredibly dirty weapon, which is a requirement for military applications.

308 Winchester (SAAMI)

Headspace v.s. 7.62 NATO (Military) Headspace

GO 1.6300" v.s. GO 1.6350"
NOGO 1.6340" v.s. NOGO 1.6405"
FIELD 1.6380" v.s. FIELD 1.6455"

Cartridge Case Construction:

Commercial 308 Winchester cases are able to contain approximately 58 grains of water, on average. The average for Lake City 92 cases, according to my measurements approached very close to 56.2 grains of water, and for NATO marked cases which are Berdan primed, the average was close to 55.9. All brass had been fired once was sized with the same die, a Hornady New Dimension 308 Winchester die.

These water measurements indicate that, for the military cases, the brass is thicker. This finding was not unanticipated, as the military brass weighs more, and the military specification calls for the “beefing up” of the area around the web for the purpose of providing an additional safety margin in case the cartridge is fired in an automatic weapon and the charge is ignited before the cartridge is completely in battery in said weapon.
This characteristic also has implications for hand loaders and other enthusiasts where pressure is concerned.
__________________
By the choices we make, we define ourselves, thereby revealing what we truly care about.

Last edited by blacksky; November 26, 2011 at 08:44 PM.
blacksky is offline  
Old November 26, 2011, 09:09 PM   #12
Ignition Override
Senior Member
 
Join Date: February 18, 2008
Posts: 1,774
blacksky: Thanks very much. You helped to explain some basics in a nutshell.

Last summer my first Spanish FR8 failed the .308 No-Go gauge, according to the gun smith. He told me that this is often the case in NATO chambers. I ordered a .308 Field Gauge from either Numerich or Brownells, and with this Field the bolt only turns a small bit.

My recent, second FR8 does even better with the field. The bolt will not turn one bit. Both bolts match, learned that a mis-matched bolt can undergo extra stress due to uneven bolt lug contact, even with nice results from a Field gauge.

Hours of research last summer revealed than when military 'cup' adds the normal 10,000 factor
to equal commercial psi,
the max. NATO 7.62 is about 58,000 max. psi, and commercial .308 about 62,000 psi max.
The test pressures are far higher. Correct me where some of this might not be accurate.

Luckily the FR8 is built on the later Spanish 8mm Mauser, which is much stronger than the old (1916) 7mm Spanish Mauser, used for the FR7's action

Last edited by Ignition Override; November 26, 2011 at 09:18 PM.
Ignition Override is offline  
Old November 26, 2011, 11:26 PM   #13
Jason_G
Senior Member
 
Join Date: December 18, 2006
Location: Louisiana
Posts: 1,902
Quote:
Springfield claims that only 7.62 NATO/Military ammunition (factory) should be fired in the M1A.
They do not mention head spacing or other issues of measurement but instead refer to the PRIMERS.
Yeah, but that really doesn't have anything to do with the cartridge dimensions, just differences in primer hardness between NATO ammo and commercial ammo. Sometimes commercial ammo uses soft primers, and the firing pin in an M14/M1A is free floating in the bolt. When the bolt slams home to chamber a round, the pin moves forward due to its own inertia. Usually not an issue, because it's light, and there's usually not enough inertia to cause a significant strike on the primer, and so it doesn't go off. If the primer is really soft, then you could potentially get a slam fire. If you look at a round that has been chambered in your rifle, but not fired, you will notice a shallow dent on the primer from the pin. That's why they throw in the lawyer language CYA statement about the military ammo. NATO ammo typically uses harder primers.

Slam fires aside, your M1A should be headspaced between 1.631" and 1.632", which is the window you want to be in to shoot either 7.62 NATO or .308 Win. A call with SAI will confirm that either should be fine in the rifle. Always keep your rifle pointed downrange, and there's nothing to worry about if using .308. JMHO, YMMV.

Jason
__________________
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." -Amendment II, Constitution of the United States of America
Jason_G is offline  
Old November 27, 2011, 06:16 AM   #14
Tim R
Senior Member
 
Join Date: November 30, 2004
Location: God's side of Washington State
Posts: 1,601
Quote:
Springfield claims that only 7.62 NATO/Military ammunition (factory) should be fired in the M1A.
They do not mention head spacing or other issues of measurement but instead refer to the PRIMERS.
They insist that the military primers are harder and resist primer detonation caused by the firing pin which slightly (or more) impacts the primer when the bolt slams forward. (slam fire)
Along with the slam fire, the gun still has to have the proper powder burn rate just like the M-1 Garand. Not every 308 out there meets the powder requirements. However

At a military rifle match, we where issued Federal Spun shut ammo to shoot in the match with our tuned M-14's. It came in red boxes with FEDERAL on the box in big whte letters. I always hated that stuff.

The 168 SMK's were spun shut so it could be fired at enemy troops and not be a hollow point.
__________________
God Bless our Troops especially our Snipers.
Tim R is offline  
Old November 27, 2011, 10:10 PM   #15
Departed402
Senior Member
 
Join Date: September 25, 2009
Location: Nebraska
Posts: 865
So if you had to explain .308 and 7.62 NATO interchangeability to a 5-year-old you would say? More specifically, if that 5-year-old was talking about AR-10 type rifles.
__________________
Slow is Smooth. Smooth is Fast.
Departed402 is offline  
Old November 29, 2011, 03:53 PM   #16
Departed402
Senior Member
 
Join Date: September 25, 2009
Location: Nebraska
Posts: 865
See, you ask for a simple answer and nobody has one. Anyone?
__________________
Slow is Smooth. Smooth is Fast.
Departed402 is offline  
Old November 29, 2011, 08:32 PM   #17
jonnyc
Senior Member
 
Join Date: July 20, 2009
Location: PA
Posts: 825
First off, I don't know any 5 year-olds with AR-10s, but if I did, I would tell them to read all the posts above. If they're smart enough to handle a full battle rifle, they're smart enough to have understood that there is no difference and the two rounds would be interchangeable in that rifle.
jonnyc is offline  
Old November 29, 2011, 10:39 PM   #18
Gunplummer
Senior Member
 
Join Date: March 11, 2010
Location: South East Pa.
Posts: 1,450
Bedlamite had a very good post. Go back, pop up the add ons and look close. This argument has been going on for years. There is no simple answer. The answer is always "sometimes". I dealt with these gages for years, and most people using them don't even know what the numbers mean that are on the gage. The military does not even use the same point on the gage to seat against the chamber that SAAMI does. If you take a loaded round that is all the way on the low specs and stick it in a chamber that was cut on the max specs, there could be a serious problem. Add in the European specs and you could get real serious problems. I almost never checked a Mauser that did not fail a SAAMI gage test on the No Go. The previous posts are pretty good. If you can't grasp what is going on with something, get help or don't mess with it.
Gunplummer is offline  
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:03 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2014 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Contact Us
Page generated in 0.10352 seconds with 7 queries