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You would think I would have run across this before. Maybe but not this obvious. Everybody is at Camp Perry except me so I'll pose this question here. I have been shooting a FN SCAR 17s. During my last range trip I took my Moe's gauge to check case expansion of my handloads. Most of them measures between 3 and 5, a couple measured 6. This was LC 07 that had been re sized to 0. I also had shot about 300 rds of W German surplus MEN 94 DAG 94 and DAG 68. Prior to firing most of the W German stuff measured 0 on the gauge.After firing none of the W German stuff would fully seat into the Moe's gauge. At first I thought the case at the web had expanded due to the chamber being 7.62X51 NATO. But closer exam I noted the base of the case neck to have an area of expansion that was probably the culprit. The pics show this. I have included , 3 cases 2 fired one not. Left is the LC 07 and LC 90 Match handload, the right is the W German DAG 94. It is berdan primed so I am not going to reload it , but the difference in the cases, and that they won't enter the Moe's gauge fully, concerns me a little. There are no other signs of pressure. The W German Ammo is really very accurate and has proved SD's in the single digits out of my Scout. Sooooo is this the result of a 7.62x51 NATO chamber being a tad bigger in the front end? And My gauge being a .308 Win.
 

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You can go to the websites of several reamer manufacturers: Clymer, Manson, Pacific etc. and pull up the specs for the reamers.

The headspace gauges for .308Win. and 7.62x51 NATO are interchangable. That doesn't mean that body/neck diameter tolerances are the same.

Perhaps there's an alternate explanation: brass hardness/content. The Bundeswehr is planning on trashing the empties, they may not spring back toward original specs as much as other brass.
 

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Externally, there is no difference between Commercial 308 Win ammo made to SAAMI specs and 7.62x51 ammo made to NATO specs.
However, the difference is in the chamber. 7.62x51 NATO chamber is longer than a Commercial 308 Win chamber.
There are 3 headspace gauges for each one, GP, NO GO, and FIELD. When a rifle chambers a FIELD gauge, it is getting close to dangerout headspace. Having said that, a 7.62x51 NO GO gauge will often swallow a Commercial 308 Win FIELD gauge.
NATO spec chambers are so much longer, that it is recommended that commercial ammo not be used in them, because commercial ammo has thinner brass that often won't stretch as much as the thicker military spec brass, and the commercial brass will often crack or split. Remember, I said that the external dimensions were the same? Well, interally, the military brass is thicker/heavier so that it can stretch more.
So, to answer your question, the brass from a gun with a NATO spec chamber will not go into a gauge set up for a commercial chamber. The chamber may be safe for mil spec ammo, and be within NATO specs, but fall way out of commercial specs.

http://www.gunslot.com/forum/308-and-7-62x51-same-round

http://m14tfl.com/upload/showthread.php?t=65127
 

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Thanks for confirmation of that. I will stick to GI brass for handload purposes. As an aside, have either of you tried the IVI unfired brass as being advertised by Top Brass.
 

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Sailormilan2 said:
NATO spec chambers are so much longer, that it is recommended that commercial ammo not be used in them, because commercial ammo has thinner brass that often won't stretch as much as the thicker military spec brass, and the commercial brass will often crack or split. Remember, I said that the external dimensions were the same? Well, interally, the military brass is thicker/heavier so that it can stretch more.
I discovered another effect of long headspace when I fired my Polytech M14, which would almost eat the NATO Field Reject gauge. Primers would flow and flatten. Apparently, upon ignition, the primer would first back out of the case, then the case would blow back, swaging the extended primer into every available nook and cranny. And this was milspec (South African) ammo, too!

After replacing the bolt with a USGI TRW, which wouldn't close on a NATO NO GO, fired primers of the same ammo looked perfectly normal, with no flattening whatsoever. Also normal-looking primers with US commercial .308 ammo as well.
 

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I never used any IVI 7.62, but have loaded both 9mm and 06 brass with good results and I believe they have a good reputation.
 

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I have shot a goodly amount IVI loaded ball ammo and knew a guy who he and his son shot it in matches in bolt guns and I assume he reloaded it as well. Don't know anything negative about brass. We shot it in Canada in 82 through our Palma rifles and they took it up so I didn't keep any to reload. I still have some IVI ball somewhere.
I also have a goodly amount of IMI and it is good brass. I have no reason to believe the IVI would not be as it is NATO STANAG controlled.
 
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