[TimH]

I was looking at a Bushmaster today. The receiver is stamped .223 - 5.56. I thought these 2 cartridges were very simlilar but not interchangable. I have read this http://www.ammo-oracle.com/#diff and that is the opinion I have come away with. So why is the Bushmater stamped this way. Thanks TimH

[Jim Watson]

Because the difference is so small that unless you have a minimum .223 commercial chamber and some real junky maximum dimensions, poor bullet quality 5.56 military, they are pretty well interchangeable.

[cookhj]

if you know that you're going to be shooting surplus ammo in your rifle, it's better to use a 5.56 chamber. if you 're going to be shooting for competition or shooting only commercial loads, a .223 chamber will work fine. the 5.56 chamber is used because it'll shoot anything.

[TimH]

AR magazines will take either round....right?

[cordex]

AR magazines will take either round....right?
Yup. And the lower will accomodate half a dozen or so other cartridges too.

[ARperson]

I've heard the biggest difference between them is the pressure difference between the 5.56 and the .223.

SAAMI says that you can use .223 in a firearm chambered for 5.56, but not the other way around.

See THIS LINK (http://www.saami.org/unsafe3.htm) for this and other unsafe combinations.

[TimH]

What I don't understand why is the receiver stamped with " .223 - 5.56" Since there is a difference between the 2 cartridges you would think it would be stamped with either .223 or 5.56 not both.

So which cartridge would you use.

[Art Eatman]

For a rifle marked for both varieties of cartridge, the leade should be longer, as in the military rifle. That way, you don't wind up with a bullet that is longer or that has a more rounded ogive, locked to the lands.

It has been 30 years since I shot GI ammo through a non-military rifle, but it didn't bother my Mini-14 at all.

Art

[Jim K]

For all practical purposes, the rounds are interchangeable. I don't worry about it. Now to that question about dancing angels and heads of pins...

Jim

[BigG]

The Jims have it - and anybody else who correctly stated that there's not a dime's worth of difference between the two. If you have a super accurate benchrest rifle with a minimum 223 chamber, I guess you wouldn't want to put any GI ammo thru it anyway. Otherwise, have at it!

[355sigfan]

With the exception of some minor internal dimensions and the difference in barrel leade in some military weapons the two rounds are identical. Take a look at a sammi case gauge for the 223 then look at one for te 556 they are the same gauge.
Pat

[Ironbarr]

I chose the 5.56 stamped AR for general ammo availability since the two are close. The SAAMI specs, I thought, might limit availability or create a hardware problem with heavy use.

It always boils down to "What do want the rifle to do for you". I want flexibility. I'd hate to be in an ammo dump with cases of 5.56 and a SAAMI .223 rifle. Just wouldn't be comfortable.

MHD (My humble decision).

-Andy

[cordex]

I chose the 5.56 stamped AR for general ammo availability since the two are close.
Er ... you realize what is stamped on the lower is essentially meaningless, don't you? You could have anything stamped on your lower and it won't affect what kind of upper you put on the gun (assuming the lower is sufficiently to spec).

[Jhaislet]

I've got 5.56mm stamped on my lower too, but the .50BMG upper works just fine...Go figure ;)

[Ironbarr]

in my case - when I ordered the thing new from dealer and waited for two weeks for it to arrive from factory - I expected it to be a matching upper/lower in 5.56 (.223 useable) - as advertised.

It was - still is.

Of course, other sales could be different, huh??

-Andy

[LIProgun]

Some may find this link of interest:

http://www.thegunzone.com/556v223.html

[ny32182]

The chamber dimensions and pressure ratings are different.

All the non-specialty bushmaster barrels are chambered for 5.56, i.e., mil-spec. I don't know why they are stamped .223 as well, except maybe to alert the novice that .223 commercial ammo is fine in them.

The 5.56 military chamber is slightly more loose than a commercial .223 chamber for more reliable extraction under extended fire, and can also handle higher pressure military rounds, whereas the .223 commercial chamber is not supposed to do so.

Unless you are going to be using the rifle exclusively for long range, benchrest, slow fire accuracy, the 5.56 chamber is highly recommended.

[TimH]

Thanks!

[Art Eatman]

ttbadboy, next time you have a chance, compare the bolt's locking lugs of a bolt-action .223 rifle with those of an AR. Then, think about your comment, "...and can also handle higher pressure military rounds, whereas the .223 commercial chamber is not supposed to do so."

I really doubt that Ruger Remchester is using crappy steel in their bolts and receivers. My own view is that the bolt-action is the stronger of the two.

:), Art

[ny32182]

Well, I'm sure that some .223 rifles are overbuilt. When in doubt, its probably generally safest to adhere to SAMMI guidelines. It was not my intention to insult anyone's Rugers.:)