.308 and 7.62 compatible???
- Thread starter AHM1776
- Start date
7.62 NATO and .308 Win. are not the same thing!
.308 is loaded to higher pressures, and use of commercial .308 in a military type weapon regulated for the lower NATO pressures could cause damage. NATO ammo can be safely fired in .308 guns, but not necessarily the other way around.
The case wall thickness of milspec brass is greater than its commercial counterparts. Because of this, the interior volume of the case is decreased. Use of loads that would be within pressure specs if com. brass were used could cause seriously overpressure loads when milspec brass is used.
I had this problem once with a Steyr SSG. I had devoloped a load which gave me outstanding results using the Nosler 165gr. Ballistic Tip bullet and Remington cases. I tried this same load with some milspec brass. After firing the first shot, I found the bolt to be very stubborn, and when I finally got the bolt open and the case out, the primer was seriously flattened. I pulled some of the loads and remeasured them, but they were all within specs (I had used a trickler to get them exactly on, and I was right the first time around.) I had the headspace checked, and that was fine. That left only the different brass as the culprit. Thicker case walls = decreased interior case volume = substantially higher pressures.
More can be found at this link. Look towards the end of the piece for the part specifically about .308/7.62. http://communities.prodigy.net/sportsrec/gz-hague.html
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Shoot straight & make big holes, regards, Richard at The Shottist's Center
[This message has been edited by 45King (edited November 11, 2000).]
.308 is loaded to higher pressures, and use of commercial .308 in a military type weapon regulated for the lower NATO pressures could cause damage. NATO ammo can be safely fired in .308 guns, but not necessarily the other way around.
The case wall thickness of milspec brass is greater than its commercial counterparts. Because of this, the interior volume of the case is decreased. Use of loads that would be within pressure specs if com. brass were used could cause seriously overpressure loads when milspec brass is used.
I had this problem once with a Steyr SSG. I had devoloped a load which gave me outstanding results using the Nosler 165gr. Ballistic Tip bullet and Remington cases. I tried this same load with some milspec brass. After firing the first shot, I found the bolt to be very stubborn, and when I finally got the bolt open and the case out, the primer was seriously flattened. I pulled some of the loads and remeasured them, but they were all within specs (I had used a trickler to get them exactly on, and I was right the first time around.) I had the headspace checked, and that was fine. That left only the different brass as the culprit. Thicker case walls = decreased interior case volume = substantially higher pressures.
More can be found at this link. Look towards the end of the piece for the part specifically about .308/7.62. http://communities.prodigy.net/sportsrec/gz-hague.html
------------------
Shoot straight & make big holes, regards, Richard at The Shottist's Center
[This message has been edited by 45King (edited November 11, 2000).]
Art Eatman
Staff in Memoriam
45King, your heart's in the right place, but you don't have the cause and effect quite right. 
The external dimensions are the same.
The rifles can equally handle the pressures, nominally around 50,000 CUP, +/-.
Yes, MilSpec brass is slightly thicker and thus the internal case capacity is slightly smaller. Therefore, a handload of max or near-max powder charge in "civvie" brass will create higher pressure in MilSpec brass--so, possibly *too* high. To have equal pressures, all you have to do if you're using MilSpec brass is reduce the powder charge by two or three grains (roughly).
The pressures of factory loadings in either civvy brass or MilSpec brass is, for the .308, the same, at around 50,000 CUP.
This is not always true for the .30-'06, because of the numerous "ancient" rifles chambered for the '06. Whole different deal. MilSpec '06 was loaded to 47,000 psi (psi & CUP ain't the same. Don't ask.)
In general, all modern rifles are quite comfy and happy with working pressures around 51,000 to 53,000 CUP, as near as I can tell from the loading books. The only weakness is in the way the case-head is supported. Rifles designed to fully enclose the case-head, like the Rem700, are the strongest.
I hope I've been somewhere in the vicinity of clear...
Regards, Art
[This message has been edited by Art Eatman (edited November 11, 2000).]
The external dimensions are the same.
The rifles can equally handle the pressures, nominally around 50,000 CUP, +/-.
Yes, MilSpec brass is slightly thicker and thus the internal case capacity is slightly smaller. Therefore, a handload of max or near-max powder charge in "civvie" brass will create higher pressure in MilSpec brass--so, possibly *too* high. To have equal pressures, all you have to do if you're using MilSpec brass is reduce the powder charge by two or three grains (roughly).
The pressures of factory loadings in either civvy brass or MilSpec brass is, for the .308, the same, at around 50,000 CUP.
This is not always true for the .30-'06, because of the numerous "ancient" rifles chambered for the '06. Whole different deal. MilSpec '06 was loaded to 47,000 psi (psi & CUP ain't the same. Don't ask.)
In general, all modern rifles are quite comfy and happy with working pressures around 51,000 to 53,000 CUP, as near as I can tell from the loading books. The only weakness is in the way the case-head is supported. Rifles designed to fully enclose the case-head, like the Rem700, are the strongest.
I hope I've been somewhere in the vicinity of clear...
Regards, Art
[This message has been edited by Art Eatman (edited November 11, 2000).]