308 Winchester Vs 7.62 Nato

[AzRednek]

Good article I hijacked from another group. It is in a zip file. http://forums.handloads.com/forum_posts.as...=20557&PN=1

[tinkerfive]

Unless I missed it, he never said what the Indian spec was, all he said was that it was different from NATO and SAMMI.

 

I've had an interest in those Isapore's for some time. I'd like to have known if the chamber spec is more generous

than NATO or if were closer to SAMMI.

 

Also I wonder if doing some smith work on the Isapore Enfield to bring it into SAMMI spec would be worth while.

There was no mention of chamber diameter spec only headspace. I suspect that the diameter is somewhat more generous

as well.

 

One thing.....

Now I think that I understand why the Israeli 7.62 ( 308 W ) K98 I got closed on my SAMMI NO-GO Gage.

 

Tinker

[Larry Gibson]

Decent article and basicly correct. I've pressure tested quite a bit of commercial .308W and 7.62 NATO and know what the difference is. Only correction I would add to the article is that US NATO ammunition is now tested with a casemouth transducer instead of the CUP method he describes.

 

Larry Gibson

[AzRednek]

I've pressure tested quite a bit of commercial .308W and 7.62 NATO and know what the difference is.

Larry Gibson

 

Larry, besides the brass being thicker for military use, what is the difference? I'm just speculating but I assume the US GI ammo would likely have thicker primer cups and the bullets and primers are probably sealed. I've never encountered any problems using US 7.62 in sporting rifles but had extraction problems using German, Spanish and Israeli 7.62 in a Savage 99. The boxer primed Israeli brass worked fine for reloading. I had to use a small base sizing die before any either military or sporting brass reloads would chamber in the Savage.

[Larry Gibson]

Larry, besides the brass being thicker for military use, what is the difference? I'm just speculating but I assume the US GI ammo would likely have thicker primer cups and the bullets and primers are probably sealed. I've never encountered any problems using US 7.62 in sporting rifles but had extraction problems using German, Spanish and Israeli 7.62 in a Savage 99. The boxer primed Israeli brass worked fine for reloading. I had to use a small base sizing die before any either military or sporting brass reloads would chamber in the Savage.

 

The difference between 7.62 NATO and .308W is one of pressure. The 7.62 NATO almost always has lower pressure than .308W. Now I am talking about both types of ammo being loaded to specification here. We must understand that there is some foreign 7.62 NATO ammo that does not meet NATO specifications. Either it is loaded to higher pressure or most likely to lower pressure for use in FALs and G1s. If it is loaded to NATO specs then the velocity for 145-155 gr bullets is 2800+/- fps out of a test barrel. This correlates to 2750 fps out of most 22" barrels of service rifles like the M14. Almost all quality 7.62 NATO M80 type ball ammunition (foreign and US) falls within this specification. Pressures run 50-54,000 psi(M43) which is well within the MAP of 45-65,000 psi (depending on temperature per TM 9-1305-200) for M80 ammuntion. (also remember the 7.62 NATO pressures are measured with a case mouth transducer which gives somewhat less psi readings than case mounted transducers) Some M80 type 7.62 NATO made in those countries where the FAL or G1 was the service rifle run 45-48,000 psi(M43) with subsequant lower velocities. However, M118, Special Ball and LR ammuntion has pressures in the 55-58,000 psi(M43) range.

 

If we look at the .308W factory ammunition with 150 gr bullets we see that the advertised velocities are in the 2800-2900+ fps range. To achieve this requires more pressure. SAAMI MAP is 62,000 psi. Factory 150/180 gr ammuntion (W, F, R) generally runs 55-58,000 psi(m43). I've not found any factory ammuntion that approaches the SAAMI MAP of 62,000 psi.

 

Thus we see the difference between .7.62 NATO and factory .308W is simply one of pressure. Both fall well within the required MAPs and all .308W ammuntion I've tested so far has fallen within the MAP for 7.62 NATO. Thus shooting either one in a rifle chambered for the other should be quite safe and well within the pressure limits of the action.

 

Caveat; it was proffered years ago not to shoot WW .308W ammunition in M1A rifles. Many misunderstood this to mean the "higher pressure" of the WW ammuntion made it dangerous and this led to the urban myth that shooting any commercial .308W ammuntion in the M1A was dangerous because the .308W had "higher pressure". It did not. What made it dangerous was/is the thinner web of the WW case cold seperate damaging the rifle. It was/is the case that is the problem, not the pressure. Not the pressures of M118. Special Ball and now LR ammunition is right there with .308W pressures. With the thicker LC cases it is quite safe to shoot such ammuntion in M14/M1As. That's why the 7.62 case was designed with the thicker web. Unfortuneately the urban legend continues.

 

M99s are notorious for their lack of primary extraction. Cases also must be sized more to account for the tilting of the breach block (bolt). This usually means cases must have the shoulder set back .001-.002 more for ease of chambering. Just something reloaders have to deal with if using the very fine M99 Savage.

 

Larry Gibson

[CTI]

Ive fired a Ishapore 2A1 with commercial 308 and had no problems with it at all ,was very accurate with the iron sights. The cases showed no sign of sever bulging. They looked pretty good. The rifle was in very good to excellent condition. but thats not to say there could be some that are wore out and would be unsafe. The rifle I had now belongs to a friend of mine that is still using it and has added a scope to it and synthetic stock...

[Sailormilan2]

I have several 308/7.62 chambered rifles. A Springfield Loaded M1A, 3 Chinese made Polytech M14S(M1A look alikes) all of which have USGI bolts and proper SAAMI spec headspace, and a Tanker Garand in 308(built my self, using a 308 pull through reamer).

The Sprinfield M1A, would only reliably handle new NATO spec ammo. It did not like reloads or South African Surplus. Though there was one FTE with Radway Green, but that was after firing a bunch of SA surplus. At least one empty case, per 20 rd magazine, would get stuck in the chamber, and sometimes more often. Requiring the bolt handle to get smacked, and smacked hard, to remove the case. Reloads were sized with a Small Base RCBS dies, and trimmed to proper length. I have been told that SA surplus tends to be a bit dirtier and has a tar sealant which may cause some problems.

However, the same ammo in my Polytechs and Tanker Garand never caused a problem. They all worked well. I actually sold the Springfield due to this reliability issue. I also have a Yugo M48 with Parke Hale barrel in 308, and the only problem with that was a tight neck, causing pressure problems. Once I reamed the neck a bit, there have been no problmes.