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Posted: 3/19/2012 9:54:58 PM EDT
[#1]
Generally, it is fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester. You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into 7.62 NATO chambered rifles that have been designed for 50,000 psi max. Kind of the opposite of the .223/5.56 situation
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Posted: 3/20/2012 2:11:45 AM EDT
[#2]
Quoted:
So i am sure this has been done a million times so forgive me... I been reading all over the interweb and cant really find anything about firing each of these in the same rifle. I know all about 223/556 but nothing about these calibers. I been looking at getting an ar10. maybe a colt sp901. the colt says 308 on it. so can you shoot 7.62 safely? Armalite says" they have 7.62 Nato chambers and can safely shoot both 7.62 or 3.08 win". |
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Posted: 3/20/2012 4:37:38 AM EDT
[#3]
Which brings up another question, what round was/is used in U.S. Military .308 sniper rifles? I'm pretty sure
it's a 168 gr boattail, but what is the military designation and comparable round available to us? |
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Posted: 3/20/2012 6:19:01 AM EDT
[#4]
Despite what the internet commandos say, SAAMI says they are interchangeable.
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Posted: 3/20/2012 6:33:15 AM EDT
[#5]
Quoted:
Which brings up another question, what round was/is used in U.S. Military .308 sniper rifles? I'm pretty sure it's a 168 gr boattail, but what is the military designation and comparable round available to us? M118 or XM118 is the 175 Grain Military "sniper" round, there may be others and I am far from an expert. Edit, a Google search shows M852 is the 168 GR load. |
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Posted: 3/20/2012 8:38:47 AM EDT
[#6]
556 can fire both 223/556. and 308 can fire both 762/308? kinda assbackword but it works?
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Posted: 3/20/2012 9:14:27 AM EDT
[#7]
from ar10 faq
9. Is the chamber on an AR10 .308 or 7.62? From Armalite: All of our AR-10 .308's are NATO chambered and will accept both 7.62 and .308 ammo. The AR-10 can shoot 308 OR 7.62 NATO. The difference between .308 and 7.62 is chamber size, slight pressure differences due to powder burn rates, not external case size. Both cases will have the same external dimensions while the .308 has a slightly higher pressure 60Kish vice 50-55 CUP psi for NATO**. NOTE: This is OPPOSITE from the 5.56/.223 rule of thumb. The NATO chambers have greater tolerances to help with reliable functioning of military ammo. The NATO chamber is ever so slightly longer at .013". This is significant in that for reloading purposes, 308 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 chamber length will allow a round to chamber in an incredibly dirty weapon, which is a requirement for military applications. Also be aware this is why mil NATO brass is thicker vice 308 commercial brass. You will also see this "thicker brass fact" posted about 5.56/.223 brass which is a fallacy. **As a side note the reason the pressure issue is confusing is becuase the military measured 7.62 NATO chamber pressure (PSI) via CUP (in the 40s) vice the normal commercial rating of PSI measured (now) with electronic means. You will see many cling to the 50-55K PSI figure for 7.62 Nato becuase that is what the old Army TMs have in them. Since there is no conversion for the CUP measurement to the newer electronic measured PSI, they are two different numbers i.e no direct comparison. Many people will assume the CUP PSI is the same as SAAMI/Commercial PSI. It is not. Commercial PSI is derived from the direct pressure in the chamber through electronic means (piezo transducer or strain gauges). CUP is a crush measurement of a copper slug that has been fired, again not the same test. That means any newer weapon will be able to fire 308 Commercial ammo as manfs would not let them out the door if they could not, due to liability. Don't believe me, run the numbers/powders in any internal ballistics calculator and they will all be close to the 60K mark. BTW the proof load for the 308 commercial is 75K PSI, so don't worry about the 60K. GO GAGE CHAMBER SPEC INFORMATION (TOLERANCES FOR GOOD-TO-GO CHAMBERS) •AR-10 NATO – 1.633-1.638 (stainless steel, chrome moly, and chrome lined barrels) " 308 Winchester (SAAMI) Headspace GO - 1.6300" NOGO - 1.6340" FIELD - 1.6380" 7.62 NATO (Military) Headspace GO - 1.6350" NOGO - 1.6405" FIELD - 1.6455" 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. |
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Posted: 3/20/2012 9:38:09 AM EDT
[#8]
Quoted:
from ar10 faq 9. Is the chamber on an AR10 .308 or 7.62? From Armalite: All of our AR-10 .308's are NATO chambered and will accept both 7.62 and .308 ammo. The AR-10 can shoot 308 OR 7.62 NATO. The difference between .308 and 7.62 is chamber size, slight pressure differences due to powder burn rates, not external case size. Both cases will have the same external dimensions while the .308 has a slightly higher pressure 60Kish vice 50-55 CUP psi for NATO**. NOTE: This is OPPOSITE from the 5.56/.223 rule of thumb. The NATO chambers have greater tolerances to help with reliable functioning of military ammo. The NATO chamber is ever so slightly longer at .013". This is significant in that for reloading purposes, 308 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 chamber length will allow a round to chamber in an incredibly dirty weapon, which is a requirement for military applications. Also be aware this is why mil NATO brass is thicker vice 308 commercial brass. You will also see this "thicker brass fact" posted about 5.56/.223 brass which is a fallacy.
**As a side note the reason the pressure issue is confusing is becuase the military measured 7.62 NATO chamber pressure (PSI) via CUP (in the 40s) vice the normal commercial rating of PSI measured (now) with electronic means. You will see many cling to the 50-55K PSI figure for 7.62 Nato becuase that is what the old Army TMs have in them. Since there is no conversion for the CUP measurement to the newer electronic measured PSI, they are two different numbers i.e no direct comparison. Many people will assume the CUP PSI is the same as SAAMI/Commercial PSI. It is not. Commercial PSI is derived from the direct pressure in the chamber through electronic means (piezo transducer or strain gauges). CUP is a crush measurement of a copper slug that has been fired, again not the same test. That means any newer weapon will be able to fire 308 Commercial ammo as manfs would not let them out the door if they could not, due to liability. Don't believe me, run the numbers/powders in any internal ballistics calculator and they will all be close to the 60K mark. BTW the proof load for the 308 commercial is 75K PSI, so don't worry about the 60K. GO GAGE CHAMBER SPEC INFORMATION (TOLERANCES FOR GOOD-TO-GO CHAMBERS) •AR-10 NATO – 1.633-1.638 (stainless steel, chrome moly, and chrome lined barrels) " 308 Winchester (SAAMI) Headspace GO - 1.6300" NOGO - 1.6340" FIELD - 1.6380" 7.62 NATO (Military) Headspace GO - 1.6350" NOGO - 1.6405" FIELD - 1.6455" 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. Thanks you! S if i get that colt sp901 and it is chambered for 308. I can shoot 7.62x51 in it without problems? |
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Posted: 3/20/2012 6:42:30 PM EDT
[#9]
Quoted: Thanks. I finally found the M852 in a Wikipedia article after I posted. Not that it mattered, I don't even have a .308 now. But I hope to get another one down the road. I used to shoot Federal Premium 165 gr in my Remington 700 and it was extremely accurate. I see they now have it in 168 gr.Quoted: Which brings up another question, what round was/is used in U.S. Military .308 sniper rifles? I'm pretty sure it's a 168 gr boattail, but what is the military designation and comparable round available to us? M118 or XM118 is the 175 Grain Military "sniper" round, there may be others and I am far from an expert. Edit, a Google search shows M852 is the 168 GR load. |
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Posted: 3/20/2012 7:37:40 PM EDT
[#10]
Yes. The 7.62 NATO cartridge would be fine in the SP901 . I would recommend buying a .308 chambered rifle as it is the most versatile of the two options.
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Posted: 3/20/2012 8:01:48 PM EDT
[#11]
If the head space is set at a snug 1.6350, and that is the minimum for 7.62x51, then the rifle should be able to use most .308. The rifle may or may not chamber some surplus 7.62x51, as some of this ammo tends to be a little on the long side. If you are going to be using surplus, then it is recommended that you try a sample first. I have heard of some rifle's that ran great on Portuguese, for instance, but had problems with other surplus from other countries.
One thing I heard was that South African 7.62 ball surplus was a bit long for some rifles, but I am going by memory, and I may be wrong. Try some out before you buy is sure a good idea before you buy a thousand round case of anything. |
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Posted: 3/22/2012 2:23:12 PM EDT
[#12]
Quoted:
Quoted:
Which brings up another question, what round was/is used in U.S. Military .308 sniper rifles? I'm pretty sure it's a 168 gr boattail, but what is the military designation and comparable round available to us? M118 or XM118 is the 175 Grain Military "sniper" round, there may be others and I am far from an expert. Edit, a Google search shows M852 is the 168 GR load. M118LR is 175gr SMK. M118SB and M118MATCH is 173gr FMJ. M852 is 168gr BTHP. They have some new sniper stuff out now, I forget the designation... All the above have been used at one time or another, along with regular old M80. They are all available to us. |
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Posted: 3/25/2012 10:37:29 AM EDT
[#13]
Quoted:
So i am sure this has been done a million times so forgive me... I been reading all over the interweb and cant really find anything about firing each of these in the same rifle. I know all about 223/556 but nothing about these calibers. I been looking at getting an ar10. maybe a colt sp901. the colt says 308 on it. so can you shoot 7.62 safely? Fulton Armory has a FAQ on the subject. The short story is 7.62 NATO can be out of spec for a 308 WIN chamber, but usually it is not. It would seem prudent to gage a few rounds before using them. |
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