A new twist on .223 vs 5.56?

Discussion in 'The Ammo & Reloading Forum' started by gdmoody, May 5, 2011.

  1. gdmoody

    gdmoody Moderator Supporting Member

    Sep 7, 2007
    Athens, Georgia
    It was the strangest thing I have ever seen. I woke up about 2:00 this morning thinking about .223 vs 5.56. I haven't loaded any .223 in a couple of months so I don't know why I would think of this in the middle of the night.

    I have an AR15 that I know I can shoot either one in (5.56 or .223). I have a Weatherby chambered for .223 so I know I can't shoot 5.56 in it.

    This is what I woke up thinking about . . . If I take 5.56 brass and load it to .223 specifications, why can't I shoot it through the Weatherby? My answer to myself was . . . yes I can shoot it in the Weatherby.

    What do ya'll think about that??

    I know that this has probably been talked about before but I can't find this specific question.
  2. Double D

    Double D Administrator Staff Member Supporting Member

    Jul 16, 2009
    North Florida
    I am no pro but I would guess that is fine. I have had this discussion with many people and in the end there is always division on what can and cant be done. I know a machine shop / smith guy that says he shoots 556 in his ruger 223 and has done it for years without any problems. So, the debate continues george.....

  3. American Leader

    American Leader Well-Known Member

    Mar 1, 2011
    I actually load that way George. 5.56 brass trimmed and sized .223 and loaded to .223 specs. I have to admit they seem louder and stronger, but they shoot well. My understanding is 5.56 brass is a little heavier which lessens volume creating more pressure etc. Anyway, it works but if it causes any problems with my firearms I don't know yet. I shoot .223 in Ruger Mini 14 and Rem 700. I always read what I can on this subject and have never found loading data for 5.56, only .223? Good luck gd.
  4. steve4102

    steve4102 Former Guest

    Jan 27, 2006
    The Mini-14 (not Target Model) is chambered in 5.56, it does not say this on the rifle, but it does say this in the manual.

    5.56 Brass having less case capacity than 223 brass is an Internet Myth that will not die. It stems from the fact that Military 308 and 30-06 brass has less case capacity that civilian brass, so many think this applies to 5.56 brass as well. When in reality just the opposite is true, in fact most 5.56 Military brass has more case capacity than it's civilian brother.


    From Sierra.

    The conventional wisdom to reduce loads with military brass is familiar to most reloaders and is generally good advice. The rationale here is that the military cases tend to be somewhat thicker and heavier than their civilian counterparts, which in turn reduces capacity and raises pressures. This additional pressure normally requires a one or two grain reduction from the loads shown in most manuals or other data developed with commercial cases. While this is most often the situation with both 308 Winchester and 30-06 cases, it is less true with the 223 brass. We have found that military cases often have significantly more capacity than several brands of commercial brass. Again, take the time to do a side-by-side comparison of the cases you are working with and adjust your load as needed. There may be no need for such a reduction with the 223. Know your components and keep them segregated accordingly.



    There are no 5.56 dies manufactured that I know of. No reason for them as the external dimensions of the 5.56 are identical to the external dimensions of the 223. As you can see 5.56 brass has more case capacity that 223, the dimensions are the same, so size em and load em, they are the same.
  5. myfriendis410

    myfriendis410 Member

    Mar 30, 2011
    Lompoc California
    I've had this topic come up several times. Finally I had to get out our copy of "Cartridges of the World" to prove they're the same.

    You might argue the LOADING for 5.56 is specific (and it is), but exterior dimensions are identical for both cartridges and indeed they are entirely interchangeable.
  6. American Leader

    American Leader Well-Known Member

    Mar 1, 2011
    Thanks for the extra reads Steve. I have loaded maximum loads including compressed in 223 military brass and have experienced no problems as yet. Don't plan on changing, but as George said, this topic comes up alot. Doubt our opinions or experience will allow him to sleep better, but you never know!
  7. polishshooter

    polishshooter Well-Known Member

    Mar 25, 2001
    The question about 5.56 vs .223 is NOT about cases, but DIMENSIONS of the CHAMBERS.

    5.56 Chambers ARE bigger than .223 Chambers. PERIOD. You can MEASURE the difference.

    5.56 NATO chambers are made that way to accomodate the variances that may occur in manufacturing ammo from ANY NATO member supplier, on the theory that ANY NATO member can use ANY other NATO member's AMMO.

    The .223 Remington Chambers are made to SPECIFIC SAAMI specifications, which are a LOT "tighter" than specifications for NATO ammo....

    Any 5.56 chamber can fire ANY NATO or .223 ammo without any problems...

    A .223 chamber MAY fire any .223 or NATO ammo without a problem...BUT there is a chance some NATO ammo will NOT fit A SPECIFIC "tighter" .223 chamber, and produce higher pressures....NOT because NATO ammo is more powerful (most military ammo is NOT loaded to velocities and pressures that the .223 CAN be loaded to...)

    ...but the chance that the NATO round may not FIT in the .223 chamber properly is the problem...

    Bottom line, you want the most accurate AR you can have, and want 1/2" to 3/4" groups, get a .223 Chamber, shoot only civilian .223 Remingtom ammo, or full lengthsize and trim your cases, (NATO or otherwise, it WON'T matter) to .223 specs, and RELOAD to .223 specs....

    You want to shoot beaucoup rounds of the cheapest surplus NATO ammo from any source you can find it, including steel cased Eastern European Stuff....? And with good ammo you will be HAPPY with maybe a little over 1" groups?

    Get a 5.56 chamber....

    Or else get a Rock River chambered in .223 Wylde...an old wildcat just a LITTLE tighter than NATO chambers, but just a LITTLE "looser" than a .223 Remington...

    There is a REASON Rock River spent good money on that chamber...the best of BOTH worlds....

    That's why when I build or buy my "Varmint" upper it will be a Wylde... I want the accuracy, but in a pinch, (ie, Socio-Economic Collapse?) I will want to be able to shoot ANY ammo I can find, even el cheapo steel Wolf or Tulammo rounds through it.....
    Last edited: May 6, 2011
  8. steve4102

    steve4102 Former Guest

    Jan 27, 2006
    My understanding is that the 5.56 chamber is slightly larger for continued reliability in a dirty battlefield situation and has little to do with using out of spec ammo. A tight chambered battle weapon is a recipe for disaster.
  9. kentuckyrifleman

    kentuckyrifleman Member

    Feb 19, 2011
    I have a lot of research on this question (including reading SAAMI publications) and actually comparing the dimensions of the 2 cartridges and I must say that Polishshooter comes the closest to what I found (but he is wrong on one thing).

    1.The cartridge cases are absolutely identical. Check the drawings for yourself.

    2. There is no clear consensis on military brass being thicker (and lower capacity) in this caliber. For everone who says yes, there is someone who says no. I have never checked, so I won't comment.

    3. The difference is entirely in the leade of the chambers. 5.56 chambers have a much longer leade that .223. The leade is the distance the bullet travels after leaving the case and engaging the rifling. This is probably to allow interchangabity between bullet weights and could also aid in reliablity in selfloading guns.

    4. Polish, you got it backwards when you said .223 is higher pressure than the 5.56.

    SAAMI Specs:

    .223 50,000CUP max pressure
    5.56 60,000cup max pressure

    So, my conclusion is:

    .223 in 5.56 chamber is ok (lower pressure, longer leade will not hurt anything except accuracy)

    5.56 in .223 chamber is DANGEROUS (higher pressure round, bullet leade too short)

    Please do no listen to anyone who tells you they are interchnagable both ways. Leade is very important in pressure and 10,000cup is an enormous difference.
  10. permafrost

    permafrost Active Member

    Feb 24, 2010
    Oklahoma, USA
    Totally agree. This has been my findings as well. Apparently the higher pressure 5.56 nato round can actually touch the rifling when chamber in a 223 (shorter leade) chamber. Pressure spike before bullet can begin travel.
  11. davelp

    davelp New Member

    Apr 17, 2011
    I'm really getting a headache from this argument, bottom line for me is that the AR-15 is a rifle designed to be a military arm ( don't give me the m-16/m-4 ain't a Ar-15 speech please) if it can't digest military ammo, throw that receiver in the recycling, and buy one that does, most people are buying AR's for when the proverbial sh*t goes down theory so when that happens, you better have something that will cycle anything you can get. My CMMG says using Wolf ammo voids the warranty, well, I can see that with the lacquer coated stuff, it gets hot and melts in the chamber. but, myself, I PREFER to use brass cased ammo, I plan on shooting some steel cased through it just for a test, if it don't work, I'll replace the receiver with something else.
  12. myfriendis410

    myfriendis410 Member

    Mar 30, 2011
    Lompoc California
    Interesting subject. I don't own or plan to own an AR, but it just points up the idea of doing all of your homework.

    I would theorize that a long leade would allow for lower overall pressures, especially in a hot chamber/barrel of a military weapon. Weatherby is famous (or notorious?) for having a long freebore in their rifles to allow for huge powder charges and very high velocities. Accuracy may suffer as a result. And usually does.....
  13. JLA

    JLA Well-Known Member

    Feb 26, 2007
    Heart Of Texas
    .... but then again weatherby isnt known for making benchrest guns. they are a hunters brand, Where minute of grapefruit is OK. ;)

    I have gotten decent accuracy with Wby chamberings (.224 weatherby mag and .270 weatherby mag) but both required seating heavy as the twist rate allowed bullets run as far out of the case as possible, and accuracy still wasnt quite what a nice tight chambered savage with a normal amount of freebore can do with premium factory ammo.
  14. CampingJosh

    CampingJosh Well-Known Member

    Sep 25, 2007
    CMMG also says that using reloaded ammo voids the warranty, and they sell once-fired brass right from their website. It's all lawyer nonsense.
  15. myfriendis410

    myfriendis410 Member

    Mar 30, 2011
    Lompoc California
    Interestingly the Vanguard is a tighter chamber with much better accuracy potential than the Mk V, but my buddy's .340 Wby mag Mk V shoots 1/4" 200 yard three shot groups using a Barnes TTSX and Norma brass. Really an outstanding shooter, but it took 25 different bullets and as many powders to find that out. It's his 600 yard elk rifle and with it he shot his last bull, a 6 X 6---at 19 yards!
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