5.56 and .223 cases the same?

[Springfield]

I tried to shoot my 300 BLK to day and had some dissappointing results, but my main question is this: Do I need to separate my 5.56 from my.223 brass before I convert it t 300 BLK? Someone told me that today and he is pretty knowledgeable about most things so I didn't want to argue with him. Seems to me just the chambers are different, but he said that the 5.56 military brass is thicker. I am no AR expert, so how about enlightening me. And as to the results, I was trying some Unique in the cases(7,8 and 9 grains with a 175 grain bullet) and most of the time the bolt would start to unlock and then jam, enough so that it was very difficult pull the bolt back to extract the brass. Another guy said I needed WAY more lube on the bolt, what do I know, I was taught to lightly lube things, not drench it. Maybe that doesn't work on AR's. The bolt goes forwards and locks easily enough empty and when single loaded. And the cartridges drop into the chamber just fine when single loaded. Bad choice of powder? Turn up the adjustable gas port more? Just needs to break in? All the bullets hit a 8" plate at 50 yards just fine, at least no shotgun patterns.

[GRUMPA]

The main important factor when converting those is the head stamp. I make those all the time and foreign garbage goes in the garbage. Other than your loads you should be good to go.

[WILCO]

Seems to me just the chambers are different, but he said that the 5.56 military brass is thicker.

http://www.luckygunner.com/labs/5-56-vs-223/

[mac1911]

the chambers are different....as for the rounds. From all I have come to understand is 5.56 NATO cartridges are loaded to a higher preasure than saami 223 reminton. When this comes into play is when the lead or throat is shorter in a particular chamber.
I dont think you will find a substantial difference in the actual case demensions.

http://www.thetruthaboutguns.com/2013/02/foghorn/ask-foghorn-whats-the-difference-between-5-56-and-223/ take it for what its worth.

[nhrifle]

Correct! Chamber pressure measurement (CUP vs. PSI) is the defining factor between .223 Rem and 5.56 NATO, but 5.56 chambers do have a longer leade to allow for the higher pressures achieved with 5.56.

I have converted many brands of brass to 300 AAC and so far the only one that has given me any problem is PMC. It is good brass, but when converted gives thicker necks and resultant chambering issues. I save that for loading .223.

[Gtek]

I am glad to hear that from someone else on the case thickness issue when converting. I chimed in on this a while back and was "informed" that there is not a problem/issue. I had to then just assume my mic's were having a bad day. Thanks nhrifle- Gtek

[Jailer]

Correct! Chamber pressure measurement (CUP vs. PSI) is the defining factor between .223 Rem and 5.56 NATO, but 5.56 chambers do have a longer leade to allow for the higher pressures achieved with 5.56.

I have converted many brands of brass to 300 AAC and so far the only one that has given me any problem is PMC. It is good brass, but when converted gives thicker necks and resultant chambering issues. I save that for loading .223.


I am glad to hear that from someone else on the case thickness issue when converting. I chimed in on this a while back and was "informed" that there is not a problem/issue. I had to then just assume my mic's were having a bad day. Thanks nhrifle- Gtek

Case neck thickness is an issue as others have mentioned. Add PPU to the list of brass not suitable for conversion.


I tried to shoot my 300 BLK to day and had some dissappointing results, but my main question is this: Do I need to separate my 5.56 from my.223 brass before I convert it t 300 BLK? Someone told me that today and he is pretty knowledgeable about most things so I didn't want to argue with him. Seems to me just the chambers are different, but he said that the 5.56 military brass is thicker. I am no AR expert, so how about enlightening me. And as to the results, I was trying some Unique in the cases(7,8 and 9 grains with a 175 grain bullet) and most of the time the bolt would start to unlock and then jam, enough so that it was very difficult pull the bolt back to extract the brass. Another guy said I needed WAY more lube on the bolt, what do I know, I was taught to lightly lube things, not drench it. Maybe that doesn't work on AR's. The bolt goes forwards and locks easily enough empty and when single loaded. And the cartridges drop into the chamber just fine when single loaded. Bad choice of powder? Turn up the adjustable gas port more? Just needs to break in? All the bullets hit a 8" plate at 50 yards just fine, at least no shotgun patterns.

First off, no difference in 223 and 5.56 brass. All brass will have slightly different case capacities but there isn't a "separate" 5.56 spec brass.

As previously mentioned, brass manufacturer does matter when converting 223 brass to 300 blk. Neck thickness on the final product is the issue and can cause chambering issues and high pressures if the necks are too thick.

Unique is a great powder but a lousy choice for an AR. You need to use a powder in the burn range for the cartridge if you want the action to cycle properly. LilGun, H110/296, 4227, 300MP, 4198, 1680 and RL7 are some of your choices. You'll have to experiment to see what works best in your gun with your gas system (carbine or pistol).

Good luck.

[uscra112]

.223 and 5.56mm brass same?
NO,
simple test for you ---- weigh the differant cases notice the weigt differance. Then weigh the case zero your scale fill with H2O to the top of the necks notice the differance in volume. The 5.56mm should be less water meaning less internal volume which equals higher pressure. Now some on the errornet have argued with my statement saying that LC cases are not that way. What I am saying here is what I have observed you may observe differant results
Good Luck
Mike

Well, Mike, I actually sorted a large batch (2000+) of range brass a while ago, then did a careful comparison of weights. (Metrology was a large part of my career, and I find it hard to give it up.)

In my samples, LC 5.56 (random years), FC 5.56 and R-P .223, WW .223 commercial, average weights of the four samples varied less than the extreme spread within the samples, which, including outliers, was as much as 4 whole grains.

There were some FOREIGN 5.56 and commercial .223 cases that were a lot heavier, but I had only half a dozen of each so did not record that data.

Did the water-weight test on a few as well, and found that dry weight is very closely correlates to internal capacity. So using dry weight as a sort criterion is valid. This is good, because getting cases filled exactly the same is tedious to say the least!

My conclusion is that, so far as American makers are concerned, there is no difference, and if you really care about case capacity, get out the scale and actually sort what you have, at least to eliminate the outliers.

From my "big bag o'brass", of the four headstamps mentioned, I got 1133 that were within a range of 92 to 93 grains. (All weights are deprimed and after wet-pin tumbling and drying.) Another 450 or so were one grain or less heavier or lighter, (i.e. 91-92 or 93-94 grains) and 107 were real outliers - either lighter or heavier than the middle group by 2 grains. Scrapped the outliers, sold the "light" and "heavy" batches during the famine, kept the 1133.

The remainder of the 2000+ were PMC or foreign makes in such small numbers that I did not tally. I remember one of those foreign ones, (CBC?) was about 97 grains!

p.s.
When I weighed some .30-06 cases, (sample size 20), the LC Match average was actually LIGHTER by 3.6 grains than the sample average of some Federal civilian cases. Min-Max spread and StdDev of the LC batch was slightly better, though.

Don't have any LC 7.62x51 cases, so I can't comment.

[Springfield]

CBC is much thicker in 44-40,45 Colt and 38 special also, so much so that a friend of mine can't even chamber CBC brass in his 38 sp Uberti rifle, as it has a very tight chamber. Doesn't work in some of my 44-40 pistols also, so I toss it whenever I find it. As to powder, I am trying to make some "plinker" loads for my wife to shoot, and I have an adjustable gas port. h110/296 is a bit temperamental about light loads, from what I have read. Need a good midrange powder. I oiled the snot out of the bolt, it works MUCH better now.

[M-Tecs]

Case volume is the same or slightly greater for the 5.56. I have compared numerous years of LC & WCC GI brass to Winchester, Remington, PMC and Federal. It's basically the same with Federal having the least volume.

In the 308 and 3006 I have found that the military brass does have less case volume. I have never found a difference with the .556.

More info here http://www.6mmbr.com/223Rem.html

Good post on the subject.

http://castboolits.gunloads.com/showthread.php?154028-Confusion-over-the-whole-223-vs-5-56-thing…&highlight=Confusion+223+vs.+5.56+thing%85

[uscra112]

Blue Dot / AA#9 / 2400 my choices in order. Blue Dot is faster than the other two. Drop 2 full grains from the 2400 loads you find in manuals. But should work better in reduced loads.

I like B.D. for boolit loads in my Krag and the K-31 Swiss so much that I bought a keg of the stuff. A serious military C.B. target shooter I know tells me that B.D. is the powder of choice for more than a few of his colleagues.

[Springfield]

So it looks like I should weigh all my cases and throw out the big offenders. I don't load for maximum, that is the whole point for me in doing 300BLK, I don't have to strain things to get good results.

[uscra112]

Ok looked at the Data sheets (Technical Manual aka TM for Ammunition) and acually found the answer we are all correct M193 is heavier and less volume than M855 and the approved deviation of the TM known as commercial pack since 2005/2005.

So we're both right, then.

And given the 3-4 grain Min-Max range in any lot, it's worth doing a weight-sort even if you know what you have and they're all the same headstamp.

[nicholst55]

With all that said I know that there was thicker brass made back in the day and unless you weigh every case or read every headstamp for the date I really do suggest that it is treated as less volume.


Interesting, and something that I was not aware of. I have a bag of once-fired brass that dates from the 70s somewhere. I'll have to dig it out and weigh the brass. I have weighed numerous samples of different headstamps of 5.56 and .223 brass before, and reached the conclusion that US-manufactured brass shows very little difference. Foreign-made brass is a whole different story.

CBC 7.62mm brass, FWIW, is extremely thick and notoriously difficult to size. The same with CAVIM 7.62mm brass.

[M-Tecs]

I have both M193 and M855. The M855 is mostly newer starting at 95 with most years to 2010. The M193 starts at 1979 and goes to 2003. I have found all LC .556 brass to be remarkable consistent for both weight and volume. I do have some AA40 5.56mm frangible ammunition from 2004 that is the heaviest and least volume of the bunch. I see more variation between commercial 223 brands than I see with M193/M855 of various years.

I have a couple of questions not related to this and I would love to review the Technical Manual Data sheets. Where can I find this info?

For redline loads for highpower during the 90’s the new LC primed and crimped brass was preferred because it was believed to be harder than commercial. I never tested it so I don’t know if it was true or not. I didn’t really care since I was still shooting my issued M-14. I do know that during the 90’s the Army and Marines were shooting some very “hot” loads on crimped and primed new LC brass. It was not suitable for reloading after one firing.