7.62 NATO vs .308 Win brass

[am44mag]

So, I have not been able to find a definitive answer on this. Is there really a difference in 7.62 NATO and .308 Win brass, or for all intents and purposes, are they the same? I've read claims that the 7.62 brass is thicker and will need to be downloaded, and I've read claims that the difference in thickness is negligible. The internet being what it is, people love to pass along myths and hearsay, so I was wondering what the truth is on this.

I have a pile of .308/7.62 brass and since this is not going to be for anything even resembling a precision rifle, I'm wondering if I should even bother sorting and separating the brass. I'm going to be reloading to 7.62 NATO specs, so I'm thinking that if I do my load development in 7.62 cases, the worse case scenario at that point would be the loads in the 308 cases having slightly less pressure and a slight POI change.

[Hickory]

If I remember correctly, and my memory has been hit & miss lately, the 7.62 is loaded at a slightly lower pressure than the 308.

[Winger Ed.]

In the old Sierra loading book, they said to reduce all their data by 1 grain to compensate for the thicker GI
brass, and its influence on case volume and pressure for the same charge in a civilian case.

They had this warning on all sections that covered popular sizes of GI rifle brass.
I never chronoed any to check if it made a difference or not- I just took their word for it.

Some other older manual had that too, but I forget which one it was.
Maybe the old Hornady book, but I'm not sure.

A quick way to maybe answer your question is to take a couple, size & trim, then weigh 'em.

[kungfustyle]

Yes, separate the brass, at least for me. I bought my first 308 about 5 years ago and got some 7.62 brass from a CB member. Wow, were they hard to get sized properly to chamber in my rifle. From data in Hodgdon's reloading I started showing signs of pressure two grains before max. I know some loads from Hodgon are over pressured, several threads on this on this site, so yes, sort your brass and start at the minimum and work up. Try your own tests, load a handful of each and fire them and see what you get. Now if you are going to shoot just cast with 5 or 6 grains of some pistol powder, I don't think it would make much difference.

[Smallbore]

I had the same experience.
Lots of Lake City GI brass that is around has been fired in machine guns. Lots of headspace.
Lake City Match brass is another story and is more consistent in weight. Mine goes 177 to 179 grains.
It still needs a reduction in powder.
Smallbore

[Neverhome]

Unless you do what Winger Ed says, everything else is just internet chatter. You could even take it a step farther and check volume with water. True measurements are the only way to prove what YOU have.

[Petrol & Powder]

OK, no internet lore here, personal experience from the mid 1990's.

I had commercial Winchester cases and Lake City cases side by side. After trimming and de-priming, I noticed the brass at the case mouth appeared thicker on the Lake City. I thought that must be some type of illusion, the difference in thickness isn't going to be great enough to actually see. So I put the casings on the scale. Sure enough, the Winchester cases weighed X and the LC cases weighed X + something.
The casings were identical externally but the LC brass was heavier.

Now, the difference wasn't huge but I would be cautious if I was loading at or near max levels with NATO brass. The flip side of that coin was the LC brass was heavier but it was also far more consistent in terms of weight. I have no idea why the commercial brass would vary in weight.

And as a side note, I agree with smallbore, A lot of that LC brass was fired in machineguns. Those cases were very bad on the first reloading cycle. They needed to be full length resized to chamber and until they were fire formed in my rifle's chamber, they weren't all that great. After that first cycle, and if confined to only one rifle - it was very good brass.

[30calflash]

Win brass was some of the lightest with more case capacity than others. It was preferred for long range shooting as more powder could be used safely. Win 308 brass weighed around 155 grains iirc.

Military brass meant for use in semi and full auto rifles had a thicker/stronger case head that made the capacity less than most commercial cases. Some LC late 60's match brass weighed 177-180 grains.

Recommendations I have read were to drop the powder charge .5 grain for every 5 grain increase in case weight. I believe the info was provided by the NRA when they had a technical staff.

[dragon813gt]

To the OP, check case capacity of the cases you have. Case weight and thickness don’t matter. It’s how much each case can hold. Capacity is easy to check.

[redhawk0]

size them...then weigh each. If the GI brass is heavier...it MUST be thicker. Reduced internal volume will require a slightly reduced powder load to achieve the same pressure.

If you're not shooting at Max....its probably not worth worrying about. I relegated all my GI brass for Lead only...I use commercial brass for hunting loads.

redhawk

[popper]

You are not going to run at full load so who cares. I use LC and Win/FC all the time in ar10, SIZED correctly, no problem. Sizing as chamber is slightly different! Results @ 50, near top load with ARComp 168gr Amax, ~40 rnds. Mixed HS, unknown # firings.

[1hole]

Weighing cases only tells us how much metal each has, sized or unsized, as such, doesn't matter a bit when segregating cases by weight.

Actually, to be worth the trouble of weighing, the cases should first be uniformed. Trim-to lengths, mouths chamfered/deburred, necks reamed/turned, primer crimps removed and flash holes deburred. THEN we can learn how much our prepared cases actually weigh.

I can't believe that going from one case maker to another could cause a KABOOM unless it was already loaded to the ragged edge of loosing its togetherness. I reload but I don't run a hot-rod shop so military cases have never been a safety issue for me.

I believe the printed cautions about using GI cases are worth remembering but I suspect the real reason some manuals give those warnings is legal liability protection. No one wants to be sued by some dufus searching for reasons other than his own reloading screw-ups for blowing his rifle - plus a few fingers and eyes - from together. So, the company's lawyers (wisely) insist on a few legal boilerplate warnings that will hopefully sound good in some future tort court.

[Petrol & Powder]

"loosing its togetherness" - there's a phase I need to remember

I've seen some engine blocks that "lost their togetherness" !

[ulav8r]

I have 46 or 47 308 loads in military cases. The 3 or 4 emptys have severely flattened primers and a bright spot where the ejector hole in the bolt is located. I foolishly used the same load I had been using in commercial brass. Had to hammer the bolt open. When I get time to get back to them, I will pull the bullets and reduce the powder charge.

[Drm50]

Many years ago I used a hypodermic syringe and checked volume of 7.62 vs 308 and 5.56 vs 223.
Both militaries had less case capacity due to heavier brass. I’m not crazy about loading military 5.56. But I load 7.62 match brass for my m70fw 308. I think you would have to be loading red line 308 in 7.62 cases to see any effect. I’ve been doing it for 50yrs. I shot 150gr for about 10yrs at around 2900fps. Then switched to 130gr at approx 3000fps and have had to problems with hundreds if not thousands of rounds.

[HangFireW8]

I don't full length size MG fired 7.62 LC brass. I set the shoulder back with a Redding body die, without the expander ball that causes so much case stretch and eccentricity, then treat it like normal fired brass.

How I treat normal fired brass is another topic.

I like LC brass, a tiny bit more efficient, and after extensive first time processing, and some culling, just as accurate in anything but a full up competition rifle.

[oconeedan]

Nobody mentioned, so I will...you will have to remove the primer crimp by reamer or swager on all military brass the first time you reload it.

[Wolverine19D]

Actually the 5.56 military brass will hold more powder then 223 brass on average. At least that is the case for Lake City 5.56 over standard 223 loads. But for 7.62x51 it is the opposite and the 308 brass has more case capacity. I have heard many people say to down load by 1-2 grn of powder.

Since I haven't actually loaded any 308 yet I am curious how much more velocity you can push from the 308 brass over 7.62 Nato brass? I figure some loads the NATO brass is pretty close to the same velocity with less powder but most of the time at max pressure the 308 brass will have a little more velocity? I'm mainly asking out of curiosity for building an AR10 for long range shooting where the velocity increase could be noticeable.

[am44mag]

I plan on loading to roughly M80 specs with either BL-C(2) or H4895. I have no reason to want to push this round hard, I have other guns that will do that far better. I think what I'll do is do my load development in the 7.62 cases and see how those loads perform in the 308 cases afterwards. If they're not to my liking, I'm keep the cases separated and work up a load for them that is close to the 7.62 load.

I just got a Lyman large primer pocket reamer in the mail, so that will make dealing with the 7.62 brass easier. I usually just chuck it up in my lathe and set the speed pretty low. I've done that before with 5.56, and I can go through a pile of brass pretty quick like that.

Thanks fellas.

[popper]

I processed ~ 150 308 Win/LC/FC yesterday. Neck on Win/Fc is just a tad shorter (LC is mixed year MG stuff). It will make NO difference unless you shoot really long range! I did ~moa @ 200 with HV cast, mixed brass, no weighing bullets. brass or trickling powder. Hodgdon shows 308W and 308Win service rifle(762 NATO?), notice the 308W just has a wider spread of charge. How much difference will there be for 92 vs 94% fill? Or 84 vs 82%? None unless you get close to 100%. Neck tension will make more difference! Load mixed, shoot and look at HS after the shot. You won't see a difference.

edit: 'service' rifle rating is by the Mil to make their rifles work (op rod operated) and cycle - reliability. Unless you are shooting service rifle (tanker rifle or or class competition), why worry? M80 pulls aren't that accurate anyway. You can always tinker with the load to get POI the same.