I have lots of questions.....

[mtrmn]

Thanks for the safety concerns guys, I do know the differences in .223 and 5.56 and from what I have read, the .308 and 7.62 are basically interchangeable as per SAMMI. I have only .223 cases for my .223 and etc.... please keep info coming for me. I search and read here and other places, but as you guys know, sometimes this leads to more questions than answers.....

The CASES are not where the difference comes in. It's all in how hot you load them. The 2 rounds are essentially identical in outside dimensions--the 5.56 is loaded to much higher pressures. The 5.56 CHAMBER is essentially a .223 chamber with a much longer throat area before the bullet meets the rifling, which will handle higher pressures without an undesired event.

Just because you don't put a reloaded 5.56-marked CASE in your .223 does NOT mean that reloaded round is not loaded to 5.56 PRESSURE. A .223 case loaded to 5.56 pressures becomes a 5.56.

After over 30 yrs reloading these things I have never found any reason to load mine to 5.56 pressures because my normal .223-pressure rounds out-perform the 5.56-pressure rounds every time. Just find your accuracy node near the high end of .223 specs and call it a day.

I'm not trying to be harsh here, and I may have jumped to conclusions due to your wording. I just want you to understand now at the beginning and not find out later the hard way. This whole 5.56/.223 issue is confusing enough for those with experience.

 

[Potatohead]

my normal .223-pressure rounds out-perform the 5.56-pressure rounds every time

So, out of curiosity, why do they even load to the 5.56 pressure?

 

[Reloadron]

mtrmn states in part:

The CASES are not where the difference comes in. It's all in how hot you load them. The 2 rounds are essentially identical in outside dimensions--the 5.56 is loaded to much higher pressures. The 5.56 CHAMBER is essentially a .223 chamber with a much longer throat area before the bullet meets the rifling, which will handle higher pressures without an undesired event.

Just because you don't put a reloaded 5.56-marked CASE in your .223 does NOT mean that reloaded round is not loaded to 5.56 PRESSURE. A .223 case loaded to 5.56 pressures becomes a 5.56.

Some good words of wisdom there in my humble little opinion.

Cases loaded to higher pressures result in higher velocities. There is a general 3:1 rule of thumb here in that pressure rises 3% for every 1% rise in velocity.

Interesting reading on that subject can be found here.

I have several rifles chambered in 5.56 NATO including a beefy bolt gun. When developing loads for these rifles I have found that hotter is not always better. In fact that holds true for just about every rifle I own. When working up loads my overall experience has been that I get to a point of accuracy and then higher velocities tend to degrade the accuracy.

This all depends on the powder used and the charge weight but overall I have found that faster is not always better. That has been my experience anyway. You load to a point where a given powder with a given rifle with a given bullet deliver the best accuracy. That being my take anyway.

Ron

 

[Bovice]

So, out of curiosity, why do they even load to the 5.56 pressure?

Depending on what it's used in, it may be advantageous to have that little bit of extra pressure to make sure it cycles the weapon properly in all conditions. Remember, the military is not just shooting 5.56 from M4s and M16s.

 

[Magnum Shooter]

So, out of curiosity, why do they even load to the 5.56 pressure?

US government specifications. Your guess is as good as any as to why the government does what the government does.

 

[HOODLUM]

Mtrmn, that was the first time I have ever heard that. EVERYWHERE and EVERYTHING that I have previously read says that the leade is different and that the cases aren't exactly the same. And that is where the extra pressure comes from. As a way to shoot 5.56 in an AR that is actually chambered for .223 I have read where the chamber is opened up a little. I think it is called a Wylde chamber.... I know I have read it on the Bushmaster website as well as other places. Also, somewhere I read that the actual 5.56 cases have slightly thicker walls resulting in a reduced powder capacity, and could generate higher pressures due to a more filled case with the same amount of powder.

 

[warhwkbb]

Mtrmn, that was the first time I have ever heard that. EVERYWHERE and EVERYTHING that I have previously read says that the leade is different and that the cases aren't exactly the same. And that is where the extra pressure comes from. As a way to shoot 5.56 in an AR that is actually chambered for .223 I have read where the chamber is opened up a little. I think it is called a Wylde chamber.... I know I have read it on the Bushmaster website as well as other places. Also, somewhere I read that the actual 5.56 cases have slightly thicker walls resulting in a reduced powder capacity, and could generate higher pressures due to a more filled case with the same amount of powder.

Military 7.62 cases have thicker cases than commercial .308 Win, 5.56 not so much, many commercial 223 cases are thicker and have less capacity than Lake City 5.56 Brass. A 5.56 chamber will have a longer lead before the rifling starts. I keep the reloads for my AR-15 to 223 spec's to extend the case life.

 

[mtrmn]

Mtrmn, that was the first time I have ever heard that. EVERYWHERE and EVERYTHING that I have previously read says that the leade is different and that the cases aren't exactly the same. And that is where the extra pressure comes from. As a way to shoot 5.56 in an AR that is actually chambered for .223 I have read where the chamber is opened up a little. I think it is called a Wylde chamber.... I know I have read it on the Bushmaster website as well as other places. Also, somewhere I read that the actual 5.56 cases have slightly thicker walls resulting in a reduced powder capacity, and could generate higher pressures due to a more filled case with the same amount of powder.

Cases vary in volume, and many commercial cases may prove to actually be thicker than the mil versions. The only reliable way to find out is do your own volume testing on your brass. I'm sure benchrest shooters etc do this on a regular basis, but I don't get that anal.

In my experience, each gun seems to have 2 pressure levels/accuracy nodes where the results on target are the most consistent (accurate.) I begin finding those nodes by first choosing a set of components to test. 90% percent of my loads are military brass and bulk bullets, usually FMJ's. My seating depth is usually determined by the fact that I'll be using the rounds in a semi-auto, so I just load to maximum length that will reliably function in my magazines. Since all this is already decided, the only variable I'll change will be the powder charge.

I load like 10 rds of the starting load, jump the powder charge up 0.5gr and load 10 more, jump 0.5 gr and so forth until I reach max. Then I go to the range and fire test groups of 5 each at 100 yds. Out of these, I will pick out the best groups, usually one light load and one somewhere just short of the max. Most of the time I will opt for the hotter one as long as there are no signs of pressure.

Starting with the hotter most accurate load, I will vary the powder charge by .2 or .3 gr on both sides of that load and determine which direction I need to go to achieve better accuracy. I continue to narrow it down until I'm happy with the performance and this becomes "my load" with this particular set of components. The results go in my notebook.
Sometimes I run across a set of components that just don't like each other, so I grab another type of powder and try again.

Every AR15 I've owned over the years has been able to achieve at least 1.5 MOA at 100 yds with bulk components, and normally better than that. (My old Mini14 I used to own was the only exception I've seen. I don't think it HAD an accuracy node. But that's not the subject here.)

NEVER. Not once, have I found an accuracy node that was hotter than max .223 levels. Therefore I have completely dismissed the quest for hyper-velocity from my list of things to do. That rules out for me any 5.56 data.

I'll write another book about the 5.56 soon as I have more time. Stay tuned.

 

[mtrmn]

5.56:
I've read a lot of articles about the trials for the M16 on the net. (Sorry I don't have any references) But the most believable (to me) story kinda goes like this:
It seems there were a lot of arguments over whether the M16 and it's puny .223 cartridge were fit for adoption by the military. There was one stipulation in particular that required any battle rifle round to be capable of RELIABLY penetrating a military helmet at 500 meters. The .223 just didn't have enough oomph to consistently get the job done, so it's proponents simply decided to keep adding powder until it would meet this requirement. They compensated for the over-pressure condition by extending the throat/leade in the barrel. This allows the bullet a bit more free time before it meets the resistance involved in engaging the rifling.

Once all this R&D was done, they had to re-designate the round to distinguish the high pressure round from the normal pressure .223, so the 5.56mm was born.

If you own a 5.56-chambered rifle, go buy some factory-loaded LC (Federal) 5.56 milspec ammo and shoot some groups with it. I figure it will be mediocre at best in the accuracy dept. The military accuracy standards, although adequate for their purposes, aren't anywhere near mine.
5.56's less-than-stellar accuracy, in my opinion, is due to it being far hotter than the given gun's accuracy node and barrel harmonics.

The lack of accurate performance is why I do not condone the pursuit of extreme velocity in reloading and therefore I never load my ammo to 5.56 pressure levels. All my accuracy nodes are within .223 limits.

IMO, my rifle will never be able to reliably penetrate that 500 meter helmet if I cannot reliably HIT that 500 meter helmet. In other words, a slow accurate bullet on target is better than a screaming fast miss every time.