308 Winchester vs. 7.62 Nato

[ka0tqv]

One and the same. Yeah sure! I've been reloading for almost 60 yr's and found you can learn something new all the time. Recently purchased a Browning BLR in 308 Win cal with a handfull of loaded and mt. brass. I usually lile to use same mfr's brass when working up a new load. I'd heard that Gov. brass was heavier than commercial. Here's what I found.

WRA 65------------------------- 181 gr.
FC 308 WIN ------------------- 181.5 gr.
RP 308 WIN ------------------- 174 gr.
WW Super 308 WIN --------- 159 gr.

Wakeup call. You would have thought the 3 commercial brands would have been closer. Ken Waters wrote an article in the Feb 1967 Shooting Times called (CASE CAPACITIES). His findings vary a little, but are close to this. I looked on EBAY under 308 WIN and 7.62 Nato and found almost 4 pages of usd dies. I wondered how many were put up for sale because of erratic performance.

Would appreciate any comments and am looking for some once fired Winchester brass. Thanks CW

[JIMinPHX]

People have been telling me for years how .223 military brass is supposed to have reduced case capacity when compared to civilian brass. I've measured the case capacity of LC brass all the way from the early '70s to 2009 & found it to be about exactly the same as federal or Winchester cases & just a cat's whisker away from RP, PMC & most others. The only cases that I found to be substantially different bore a PMP or RORG headstamp. Those last two were way small. I can't fit my RE15 accuracy charge into them. It just doesn't fit.

.308 brass seems to vary more than the .223 brass does. It would appear that over the years, .308 brass has been made in a lot of places around the world & not all of them do it quite the same way. I've seem some people, who use mixed brass, take a piece of 5/16" plastic round stock with a mark on it & use it to check the powder height in their .308 cases before seating their boolits to be sure that they didn't get a tight case in the collection.

[pmeisel]

I read an article years ago in which the author had compared different manufacture and lots of rifle brass by grains of water capacity... I no longer recall which caliber. It would be interesting to build a little data base.

[Larry Gibson]

You'd be hard pressed to find a set of 7.62 NATO reloading dies. Exterior dimensions of the cartridges is the same. Interior case capacity has differed from day one. This is why the reloading manuals cautin us to reduce charges by 10% and then work up watching for pressure signs.

W-W cases in many instances in many cartridges are lighter and have greater case capcity than other makes. There are also many instances where milsrup cases are thhinner or the same as their commercial counterparts. It's been that way since long before any of us started reloading.

In the case of .308W in your BLR, a bolt action, a pump action or a single shot the use of WW cases has the advantage of greater case capacity and thus can achieve a bit more velocity than with milsurp (US Milsurp) given the same presuures using the same powder and bullets. The use of the thinner WW cases in gas guns is not recommended because of the possibility of case head seperation on firing. This is especially the case when fired in military spec chambers.

Larry Gibson

[felix]

CW, I have only one Browning of that type. It is the auto version. The chamber requires a small base die, meaning that the chamber is very tight for a commercial gun. If your gun requires the same case dimension, then thin brass would be acceptable. ... felix

[deltaenterprizes]

One gun magazine had a reloading article where the author related that he had a favorite load that was worked up in a brand of brass and replaced the old cases with with new cases of the same brand. He did not reduce the load in the new brass and work up to his favorite load and saw signs of high pressure. All components were the same except the brass cases. He decided to weigh the old cases and the new cases and found that the new cases were heavier than the old! The author recommended that publishers of reloading manuals include case weights as part of the reloading data because it is such an important factor and stressed the importance of working up a load any time you change any component.
I recently weighed some 308 Win Federal brass that was supposed to be all from the same lot and found a large variation in case weights, some were 150+ gr to as high as 176 gr.
Most of the cases were between 172 gr and 176 gr.
I know benchrest shooters that size,trim debur flash holes and uniform the primer pockets then weigh the cases and them check water capacity. Out of 100 cases they get 10 to 15 that they feel acceptable to use for match shooting, they feel case capacity is that important.

[ka0tqv]

I've quite a bit of input in less than 24 hours! One thing I've learned WEIGH ALL CASES! Tnx CW

[spqrzilla]

The recommendation that military cases were of smaller capacity than commercial ( because of thicker walls to increase reliability in machine guns ) was pretty reliable advice through at least the '60's. Mostly because of the fact that US reloaders had only a limited number of ammunition manufacturers to sort through. And it was applicable mostly to .30-06 and to a lesser degree .308 Win/7.62NATO. The source of ammunition for military cases was also more easily predicted through that period.

However, as noted, that advice has never been true for 5.56mm/.223 Rem as the cases there are not correlated from source in terms of case wall thickness.

And today, we have a lot of different sources for brass.

Know your brass is therefore a bit more work than just relyin on a rule of thumb.

[montana_charlie]

Wakeup call. You would have thought the 3 commercial brands would have been closer.
I wouldn't expect to see the same weights if the cases were all from one manufacturer...unless they were all from the same lot number.

Even then, I would weigh out a 'matched set' to use for working up a load.

CM

[miestro_jerry]

When I get a bunch of brass in, all one caliber, I sort thru them and weigh the different lots, most are close to what you would expect. The military brass seems to be the same as the civilian brass.

I will have to check some military 30-06 brass that I have from days gone past against recently manufactured commercial brass. This could be very interesting.

Jerry

[303Guy]

I have a set of PMP cases I use in my carbine for their small capacity! I'm talking big differences.

[mike in co]

as an example, accurate powders recommends a reduction of 4% when using sie 168 in LAKE CITY MATCH BRASS.

and in my case it was a perfect match.

a side note i have once fired lc 7.62x51 brass for sale on the for sale forum.

my suggestion is get a new set of dies, a large batch of brass. prep the brass as much a you plan on and then weight sort into batches.

if you start with new brass you will probably never need a small base die,but if you go for once fired, you may need to invest in a small base die to get it to fit your rifle.


mike in co

[shooting on a shoestring]

Just goes to show that trickling charges doesn't mean much if the cases aren't equally as precise.

[mike in co]

Just goes to show that trickling charges doesn't mean much if the cases aren't equally as precise.


trickling charges can be very inaccurate if one does not keep th ebeam moving.

do not add till "zero"....try it some time trickle to zero and then bump the beam and see where it settles.....
add some allw the beam to move via a bump and then add and bump.

the beam has a resitance to change, it may read zero and be over.

[Harter66]

I've shot quite a bit of GI brass in my 06' . Weighing is vital for my rifle it ain't fool proof though. As a test I put my best GI load into a Rem case of the same weight ........................250 fps slower in the Rem cases . When I water checked them the Rem cases were bigger.

As to 7.62 NATO and 308 being the same as too with 223/5.56, it is the necks that cause the issue in firing.

[mike in co]

I've shot quite a bit of GI brass in my 06' . Weighing is vital for my rifle it ain't fool proof though. As a test I put my best GI load into a Rem case of the same weight ........................250 fps slower in the Rem cases . When I water checked them the Rem cases were bigger.

As to 7.62 NATO and 308 being the same as too with 223/5.56, it is the necks that cause the issue in firing.

not.......

[frankenfab]

Certainly the case volume is a factor when reloading the brass.

As far as factory/military ammo is concerned, it was my understanding that 7.62 and 5.56 were loaded hotter in some instances because military rifles have freebore, which reduces the pressure curve. As such there is a possibility of over pressure in a civilian chamber with shorter leade. So it is the chambers that are different, not the external dimensions of the ammo.

[Doc Highwall]

I just finished weighing 400 Federal Gold Medal cases yesterday and the average weight was 176.4 grains. I separated them into several batches with 100 of them between 175.7grs to 176.1grs, 200 of them between 176.2grs to 176.6grs, 50 of them between 176.7grs to 176.9grs. I also had 20 between 175.3grs to 175.6grs and 22 between 177.0grs to 177.7grs with the rest being light. My plan is to use the small lots for testing different loads.

[mike in co]

Certainly the case volume is a factor when reloading the brass.

As far as factory/military ammo is concerned, it was my understanding that 7.62 and 5.56 were loaded hotter in some instances because military rifles have freebore, which reduces the pressure curve. As such there is a possibility of over pressure in a civilian chamber with shorter leade. So it is the chambers that are different, not the external dimensions of the ammo.

can you show me those drawings ???


freebore on a 556 ???

[frankenfab]

http://www.thegunzone.com/556v223.html

Here is a drawing with many different chamber types:

http://www.ar15barrels.com/data/223-556.pdf

[Larry Gibson]

There are numerous mistakes in that Gun Zone article. SAAMI does not track military cartridges. The "SA" in their title stands for "Sporting Arms". The SAAMI copper crusher MAP for the .223 Remington is 52,000 CUP and the piezo is 55,000 PSI. The US Arsenals use a gas piezoelectric transducer located at the case mouth for the measurement of NATO Cartridge pressures (7.62 and 5.56). The MAP for the 5.56 NATO is 60,000 PSI as measured with the transducer.

My pressure tests with numerous commercial and milsurp types of .223/5.56 show that most are loaded to around the 55,000 PSI range. I have found 1 lot of 5.56 that was loaded to very high PSI, over the MAP for that cartridge. Even the use of a chronograph and the usual visual pressure signs throw up a flag on that lot. The velocity is about 150 fps faster than it should be and the primers are very flattened. There was no CHE to indicate the higher pressure BTW. My test barrel has a milsurp speck chamber.

However, this thread is about the .308W vs the 7.62 NATO. As previously mentioned there are no external differences in the cartridge case dimensions. As some have rediscovered there are internal differences. This can affect the pressures with handloads but it does not with factory/arsenal ammunition as the respective cases are loaded to MAP specifications regardless of the case weight.

The SAAMI MAP for the .308W is 62,000 PSI (piezo) at 70 - 72 degrees. The MAP for 7.62 NATO (as per US specifications) using the case mouth piezoelectric transducer is; "from 45,000 psi to 65,000 psi, depending on temperature." My tests show that US M80 7.62 NATO ammunition pressures run in the 55 -60,000 psi(M43) range. M118 (both white box and special ball), M852 and M118LR run in the 60 -64, 000 psi(M43) range. Most foreign milsurp M80 ball ammunition runs in the 52 -56 psi(M43) range, especially from those countries that used the FN/FAL rifle. The velocities of the foreign milsurp were correspondingly lower also.

Numerous different brands and bullets weights of US commercial .308W ammunition gave pressures in the 55 - 62,000 psi(M43) range. Overall I have been unable to find any marked difference in the pressures between US Arsenal produced 7.62 NATO ammunition pressures and US commercial produced .308W ammunition. There were variances as expected but all were within the publish SAAMI and US Arsenal specifications.

My .308W/7.62 test barrel has tight bore and groove specifications (.299 x .308), a 10" twist and is chambered with a minimal spec match reamer to minimum headspace.

Larry Gibson

[Adam10mm]

Gunzone and Wikipedia are full of holes for sure.

[Char-Gar]

The 7.62 and .308 Win. rounds are the same, but the rifles are not. A rifle chambered for the 7.62 round has a slightly longer chamber. The headspace gages are not interchangable between the two. Military rifles often have a more generous chamber than their civilian counterparts.

So, if you buy GI fired brass, it will require more sizing to get it down to proper 308 size. If it was fired in a machine gun, it also might take a small base sizing die.

The old saw about GI brass being thicker is certainly true of 30-06 brass. But like others I have weighted and measured 7.62 USGI brass and found it no thicker than some makes of commercial .308 brass. Some years ago I picked up 1K LC 67 - 7.62 Nato brass for two cents each I use it in a number of different .308 rifles and am quite happy with it.

[StarMetal]

When the 5.56 was in it's infancy there were rumors then went around that the brass wasn't designed to be reloaded...that it was a once fire leave on the battlefield. That's certainly not true.

As to whether the 7.62 case is thicker then commercial cases or not I can't really say as I haven't done a scientific test on them. I can say I have some Canadian military brass that BruceB told me was good stuff. He sure wasn't kidding....it's the best 308 brass I've ever owned. I'm firing it from my MAS 49/56 and let me tell you that rifle beats up brass everywhere...meaning the rim during extraction, the dented case mouths, the violent extraction...and I've haven't lost one case nor have any of the primer pockets loosen or the neck thinned.