7.62 and 5.56 brass vs 308 and 223

[doctor_meltdown]

I recently bought the setup to start reloading but won't have a chance to start using it for a while. I'm basically just saving my spent commercial brass for future use.
A short while back I bought quite a bit of ammo from Rampart (who seems to no longer be a sponsor) which had some Aguila 5.56 and 7.62x51. I usually shoot them out of a bolt action for plinking. Generally I have been discarding the 5.56 brass that I shoot through my benelli MR1, but with the recent increase in prices in 223 ammo maybe I should start keeping them...

I'm wondering if I should I keep the 7.62 and 5.56 casings separate from .308 win and .223 rem casings for future reloading ?

 

[Gatehouse]

Yes, the internal case capacity may be quite different.

 

[doctor_meltdown]

Yes, the internal case capacity may be quite different.

thanks. So essentially I'd work up a load using the 7.62 brass and another using the .308 brass ?

 

[BattleRife]

thanks. So essentially I'd work up a load using the 7.62 brass and another using the .308 brass ?

This would be the safe approach.

However, here is something to chew on: the very common warning that military brass has less capacity than commercial arose when the most common milsurp brass on the market was .30-06. The difference then was very significant. By the time 7.62 NATO brass started to get into civilian hands the difference between it and .308 Win was less pronounced. And when the same point was reached with 5.56mm / .223 it was almost non-existant. I seem to recall one survey that found that while you might find differently with foreign makes, made-in-USA brass was likely to be identical whether it was .233 or 5.56mm.

Also keep in mind that some brass will have crimped in primers. This must be identified and removed thoroughly or you will have trouble seating new ones. Given the widespread nature of the AR-15 in the USA some ammo companies crimp even their .223 ammo, so you may already be aware of this.

 

[Maple57]

The whole 223vs556 and 308vs762 is an overblown point, but there are minor differences.

As for outside case dimensions, that goes away once fired in your rifle regardless of where you stand on the whole 556 vs 223 too hot for what rifle argument... A debate for those who flunked physics.

The only legitimate concern from a reloading point of view is basically case weight. A heavy case has less case capacity than a light case. Since military brass tends to be heavier, it will by default have a lower capacity and loads should be dialed back accordingly. Not much mind you, but a little.

But the real point here is not a debate between military brass or civilian brass, its really just due diligence that any reloader should exercise and its really about mixing head stamps of any kind.

For example... Lapua cases are heavy and Winchester cases are light. If you were to develop a load for Winchester brass and then use it with Lapua, you can expect the load to be hot, just as though you did the same with 556 or 762 brass.

What's your takeaway? Don't mix head stamps.

If you want to mix head stamps for any reason, then work up the load with the heaviest brass and then it will be safe with the lighter cases.

 

[Gatehouse]

thanks. So essentially I'd work up a load using the 7.62 brass and another using the .308 brass ?

Yes, just like you would for 2 different brands of brass. Assuming you want full potential loads with velocity and accuracy.

 

[TheNatural21]

You should treat every headstamp differently. I have milsurp brass that is light (Hirtenburger) and commercial brass that is heavy (Lapua) in 308/7.62. The trend is usually the opposite. I used to just drop a grain of powder for loading milsurp brass, but rules of thumb like that always have exceptions and in this case they can be dangerous. After seeing some wild velocity changes with different headstamps I work up a load for each, doesn't matter if it's 308 or 7.62x51.

I don't shoot much 223/5.56, but I imagine the same logic would apply.

 

[jparent]

The whole 223vs556 and 308vs762 is an overblown point, but there are minor differences.

As for outside case dimensions, that goes away once fired in your rifle regardless of where you stand on the whole 556 vs 223 too hot for what rifle argument... A debate for those who flunked physics.

The only legitimate concern from a reloading point of view is basically case weight. A heavy case has less case capacity than a light case. Since military brass tends to be heavier, it will by default have a lower capacity and loads should be dialed back accordingly. Not much mind you, but a little.

But the real point here is not a debate between military brass or civilian brass, its really just due diligence that any reloader should exercise and its really about mixing head stamps of any kind.

For example... Lapua cases are heavy and Winchester cases are light. If you were to develop a load for Winchester brass and then use it with Lapua, you can expect the load to be hot, just as though you did the same with 556 or 762 brass.

What's your takeaway? Don't mix head stamps.

If you want to mix head stamps for any reason, then work up the load with the heaviest brass and then it will be safe with the lighter cases.

Hardly an overblown point... at least pertaining to 223/5.56 5.56 chamber has a different free bore and throat angle and ammunition is loaded to higher pressure. Aside from the advice regarding brass processing, handling and mixing head stamps (all good advice). Firing a 5.56 pressure load in a 223 chamber is risking damage to the gun and operator (especially that aquila crap, it's loaded to max 5.56 pressure). As well, If you are reloading in bulk for a semi auto, your mixed headstamp may not all cycle your action if you are trying to find a "middle of the road" load that's safe for everything.

Im a brass whore so i keep everything, certain headstamps get pulled for certain loads, and others go in the bulk pile. Really just depends on what i am reloading for.

 

[KRJ]

Hardly an overblown point... at least pertaining to 223/5.56 5.56 chamber has a different free bore and throat angle and ammunition is loaded to higher pressure. Aside from the advice regarding brass processing, handling and mixing head stamps (all good advice). Firing a 5.56 pressure load in a 223 chamber is risking damage to the gun and operator (especially that aquila crap, it's loaded to max 5.56 pressure). As well, If you are reloading in bulk for a semi auto, your mixed headstamp may not all cycle your action if you are trying to find a "middle of the road" load that's safe for everything.

Im a brass whore so i keep everything, certain headstamps get pulled for certain loads, and others go in the bulk pile. Really just depends on what i am reloading for.

See I have to disagree with your point. SAAMI states that it isn't safe to do what you say. It's only really tracer ammo that's a concern(if you read their reasoning). C.I.P. consider 5.56 & 223 as equivalent. So anything imported from Europe or exported to Europe is safe to use either or.

SAAMI is not the be all end all. However to be exceedingly careful you should likely match the ammo to your barrel stamp.

However if you walk into a store today and buy a new common rifle chambered in 223. Nothing bad will happen if you shoot 62 gr 5.56 ammo through it.

 

[Maple57]

Hardly an overblown point... at least pertaining to 223/5.56 5.56 chamber has a different free bore and throat angle and ammunition is loaded to higher pressure. .

I feel like a conservative arguing with a liberal who has an opinion that is not based upon actual fact.

Higher pressure is a misnomer much like saying 1000 yards is farther than 914.4 meters. You see a bigger number and don't realize its a completely different measuring system.

Even if pressure were measured using the same method for both and even if there is a different pressure, in both cases the loads will be deemed safe. The brass would be blowing primers and showing signs of pressure regardless of the rifle it is fired in.

As for shoulder angle... seriously? Meaningless.

I've been hand loading for 40 years, designed several chambering reamers and loaded for F Class for more than 20 years, and I've heard some really crazy things over the years, but this one is the most absurd.

I know there are people in this world who are just like parrots and just repeat what they hear without giving it a thought, and this argument is clearly a debate between people who actually think and people who regurgitate.

 

[TheNatural21]

Fellas.. the question was about the difference in the brass cases for reloading, not loaded ammunition.

A different freebore can make a difference in pressure for sure. But it has little to do with the brass. Just this season I loaded up some 308 with 155 grain Hornady BTHP Match projectiles at mag length (2.800"). I was unplesantly surprised when they were crammed into the lands so hard that they were very difficult to get out of the chamber without firing them. Turns out the bullets hit the lands at 2.750" OAL. Cramming them into a smaller space pushes the bullet into the case, reducing capacity and increasing pressure. It also takes a little longer for pressure to build enough to start moving the bullet which can also increase peak pressure. I believe this is the concern with 5.56 in a 223 chamber. In my case I saw some pretty flat primers with a load that was well under max in my manual. 2.800" was the suggested OAL according to that same Hornady loading manual, so I wasn't deviating from the book. I don't recall if I was using 7.62 or 308 headstamps, but it would have been the same thing either way. From my rather limited knowledge on the topic, I believe this is only an issue with factory 5.56 tracer rounds which may be why people have no problems with 5.56 in a 223 chamber even though it is not recommended. For reloads, just make sure your loads are worked up in your rifle to avoid any of these issues regardless of what the headstamp says.

 

[maynard]

My application for brass use may be a little different than most. I always use brass from the same lot and weight sort it. .308 brass is sorted to .5 gr and .223 brass is sorted to .3 gr.
The .308/7.62 and .223/5.56 debate will go in forever. However from my experience they are interchangeable. To say shooting 7.62 out of a .308 chamber rifle or shooting 5.56 out of a .223 chambered rifle will damage your rifle and could harm the shooter, prove it to me. There must be some pictures somewhere on the WWW that you could link to this thread. The reason you read about mil-spec ammo having higher pressures is the wide range of manufacturers and quality control. I remember years ago making Mexican match out of IVI ammo. Pulling the bullet, reweighing the powder the seating a match bullet. Rounds out of the same lot, same box, same stripper clip, some had stick powder, some had ball powder. No wonder it shot 2.5 MOA.

As for the OP, at minimum sort by headstamp and develop a load the works with the heaviest brass and you shouldn't have problems with the same load in lighter brass.

 

[jparent]

I feel like a conservative arguing with a liberal who has an opinion that is not based upon actual fact.

Higher pressure is a misnomer much like saying 1000 yards is farther than 914.4 meters. You see a bigger number and don't realize its a completely different measuring system.

Even if pressure were measured using the same method for both and even if there is a different pressure, in both cases the loads will be deemed safe. The brass would be blowing primers and showing signs of pressure regardless of the rifle it is fired in.

As for shoulder angle... seriously? Meaningless.

I've been hand loading for 40 years, designed several chambering reamers and loaded for F Class for more than 20 years, and I've heard some really crazy things over the years, but this one is the most absurd.

I know there are people in this world who are just like parrots and just repeat what they hear without giving it a thought, and this argument is clearly a debate between people who actually think and people who regurgitate.

If they are so the same why do companies such as Nosler publish 5.56x45mm specific load data, and ammo manufacturers have specific 5.56mm loadings. Instead of being a typical Liberal and saying "Im right, listen to me" why don't you educate us?

 

[Potashminer]

Just a wild guess - no experience at this at all - but I think the military loads might be different from the "civilian" loads to create an appropriate range of "pulse" or "pressure" or whatever to allow the milsurp semi and full auto to function properly. Not an issue with a bolt gun. But, what do I know - I have never loaded for a semi or full auto military rifle...

 

[Ganderite]

Just a wild guess - no experience at this at all - but I think the military loads might be different from the "civilian" loads to create an appropriate range of "pulse" or "pressure" or whatever to allow the milsurp semi and full auto to function properly. Not an issue with a bolt gun. But, what do I know - I have never loaded for a semi or full auto military rifle...

Yes, this is a small issue. The military spec has a max chamber pressure and a max-min pressure at the gas port. The gas port pressure requirement has a limiting effect on suitable powders.

 

[Maple57]

If they are so the same why do companies such as Nosler publish 5.56x45mm specific load data, and ammo manufacturers have specific 5.56mm loadings. Instead of being a typical Liberal and saying "Im right, listen to me" why don't you educate us?

Oh Oh... I know this one!

For guys like YOU!

Sorry, couldn't resist.

 

[bigedp51]

The throat length effects chamber pressure, and the .223 rifles with a 1in12 or 1in14 twist rate will have the shorter throats. My Savage .223 with a 1in9 twist has a throat longer than my AR15 rifles. The SAAMI interchangeability warning for the .223 and 5.56 came out in 1980 when the M885 round was adopted. The throat was lengthened and the twist rate was changed to 1in7 and the chamber pressure increased to over 57,000 psi. Bottom line you do not want to fire M885 5.56 ammo in a short throated .223 because the chamber pressure will be 5,000 psi over max .223 pressure. And the .223 and M193 ammo are both loaded to 55,000 psi and the older M16 rifles had the shorter throat.

Below case weight and capacity of .223/5.56 brass. NOTE Lake City 5.56 cases are made of harder and not thicker brass.

If you take the top Lake City case at 30.6 capacity and the bottom Lapua case at 28.0 capacity the Lapua case with the same powder charge would be 5,000 psi higher.

Below the Lake City cases are above average compared to Remington or Winchester in quality and case weight variations.

Below case weight and capacity of .308/7.62 brass. NOTE Lake City 7.62 cases are made of harder and not thicker brass.

Bottom line, I'm a cheap bastard and I buy bulk once fired Lake City 5.56 and 7.62 brass. That way all my brass is the same, and I dont have to mess with mixed brass.

 

[Maple57]

There is absolutely no correlation between barrel twist rate and freebore.

There is no rule somewhere that states that manufactures must use a particular freebore because of a certain barrel twist rate. It is however sensible to have a short freebore for a slow twist only in the sense that a slow twist is for light short bullets, but that does not mean a longer freebore could not or would not ever be used.

A short freebore would only cause increased chamber pressure if the bullet was seated so long that the freebore seated the bullet down into the case when a round is chambered, and by a fairly significant amount. And any reasonable person would likely feel the resistance if it were the case. Very unlikely with factory ammo but possible with improper hand loads.

There are certainly differences in freebore between various rifles and manufactures are free to deviate from the drawings provided. The RPR is a perfect example of that which uses the 223 Wylde chambering.

A long freebore does not reduce chamber pressure for a load that was developed for a short freebore. The pressures will be virtually identical.

A handloader would be foolhardy to develop a load for a rifle with a long freebore and then attempt to fire it in a rifle with a short freebore, but I challenge anyone to find a factory load that is seated longer than the shortest interpretation of the SAMMI chamber.

Determining case volume by water is meaningless, although in the table above it correlates to case weight which is all that matters. A fired round expands to the chamber side walls and the limit of expansion (chamber size) is what determines pressure, more than how small the case was sized to. Yes there is a slight difference in max powder charge between a full length resized case and a fire formed neck sized case, but factory ammo would compensate for that, always to the conservative side.

The only meaningful difference between cases is the empty case weight, not how much water it holds. How much water it holds is determined by how small it was sized, which changes when its fired.

Lake city is in fact harder, on that we can agree, but it is also heavier than most other cases and therefore thicker somewhere, but mid range in the chart above. So Lake City is lighter than Lapua but heavier than Winchester... Hmmm. Does that little clue mean anything? The 556 is in between a heavy 223 and a light 223 case... So how that's a problem.

 

[bigedp51]

With Quickload one of the first things it tells you to do is measure the case capacity of a fired case. This is done to get more accurate chamber pressure readings.

Quickload defaults to the lowest case capacity of 28.0 for the .223, and the Lake City case at 30.6 capacity is 5,000 psi lower in chamber pressure.

Bottom line, case capacity affects chamber pressure and not case weight. And the design of the throat/leade will affect chamber pressure.

Ballistic Tools
https://ballistictools.com/articles/5.56-vs-.223-myths-and-facts.php
5.56MM VS .223 REMINGTON: MYTHS AND FACTS

While the specified pressures of 5.56 and .223 are the same, the pressures are measured when they are fired from the correct chamber. 5.56 can indeed be "hotter" than .223, because the leade of the chamber is designed to allow "hotter" loads with lower pressures. Pressures in any gun are affected a great deal by the throat and leade geometry, how close the projectile is to the rifling, and how tapered the beginning of the rifling is (called the leade). All of these chamber differences are further forward than any part of the chamber that the brass touches, however, which is why the brass is exactly the same.
The worst case scenario would be a full power 5.56 load, with a long bullet, fired from a brand-new .223 chamber that was cut to tight dimensions, with very little freebore, fired on a hot day, from brass with a lot of neck tension. Such a tight chamber is common on accurized match bolt-action .223 rifles. In such worst case conditions, pressures above 70,000 PSI have been reported. This is close to the proof pressure for .223, so there is potential danger firing 5.56 from a gun with a .223 chamber.

More typically, 5.56 fired from a .223 chamber exhibits classic signs of overpressure, such as excessive brass flow, expanded primer pockets, cracked case necks, stuck cases, hard extraction, and flattened primers. Since not all .223 chambers are the same, some might show overpressure signs with 5.56 while others may not. All these things happen because the brass is indeed no stronger or thicker in 5.56 than it is in .223. It's rated to take the same 55,000 PSI or so, and that's it.


Faqs – SAAMI
https://saami.org/faqs/

Can I use 5.56x45mm, 5.56 or 5.56 NATO ammunition in a firearm chambered for 223 Remington (223 Rem)?

It is not safe to shoot “5.56” “5.56 NATO” or “5.56x45mm” (“5.56”) ammunition in a firearm with barrel marked as being chambered in 223 Remington for a number of reasons. The main reason being that a barrel marked as chambered in 223 Remington will have a shorter throat into the rifling than a “5.56” barrel which may cause increased pressure when the “5.56” ammunition is fired in it. This can result in serious injury or death to the user and/or bystanders, as well as damage to the firearm.

 

[Maple57]

With Quickload one of the first things it tells you to do is measure the case capacity of a fired case. This is done to get more accurate chamber pressure readings.

Quickload defaults to the lowest case capacity of 28.0 for the .223, and the Lake City case at 30.6 capacity is 5,000 psi lower in chamber pressure.

Bottom line, case capacity affects chamber pressure and not case weight. And the design of the throat/leade will affect chamber pressure.

Ballistic Tools
https://ballistictools.com/articles/5.56-vs-.223-myths-and-facts.php

As they say... It's easier to fool someone than it is to convince them that they have been fooled.

For the purposes of quickload which is a ball parking tool, water capacity is a common unit of measurement to help understand the area inside a case. Clearly, water capacity would differentiate between a 223 case volume and a 308 case volume for example.

But... The water capacity measurement is far too crude to be used to reliably evaluate differences between head stamps of the same cartridge. A variation of the smallest drop is greater than the difference between two cases, not to mention the weight variance created by air bubbles.

Even if the water capacity was a precise method, it does not serve to support an argument for or against the differences between 556 and 223, and it's completely meaningless for reloading purposes. Even factory produced ammo will have slight variations, and loads for each would have been developed accordingly. Factories do not arbitrarily put the same load in any case regardless of case weight. Factories also use strain gages to measure the amount of pressure to confirm they are within a stress range that is deemed safe, under any weather condition such as when the round and chamber is wet, like in the pouring rain. That in and of itself is grounds to mitigate the need for concern.

Yes, I would whole heartedly agree that it is not safe to jam a round into the chamber where the load is developed for a longer seating depth than the chamber can accommodate. This point applies primarily to the hand loader as is not in support of any claim that factory produced 223 or 556 deviate in jam length to a point that warrants interchangeability concern.

As for leade angles affecting chamber pressure... This is where a little knowledge is a dangerous thing. The point is valid, in a minor way, but assumes anyone involved in load development in factories is unaware of the point and would not have adjusted for the possibility.

You can regurgitate the legal disclaimer BS all you want. Many parrots have done the same before you came along.