AR-15 Ammo question

[riderrick65]

Another new-b question. What is the difference between 5.56x45mm rd. and a 5.56 NATO rd.?

 

[HotRoderX]

nothing its just a diffrent way of saying 5.56 nato.

Kinda like 9mm is also known as 9x19

 

[Gunslinger808]

Actually there is a difference.
5.56 NATO has specific standards that it must be loaded to, the most notable is velocity.
It must be loaded to a certain velocity or higher (Mil-Spec) in order to be approved for military use.
NATO 5.56 has a circle/cross headstamp to show that it's approved.
Some commercial 5.56 is not accepted, and back in the good old days you'd find it sold loose packed with a warning on the side of the box that said "for training use only".

 

[HotRoderX]

I thought the 5.56 was designed by "NATO" (Military) so it was all 5.56 was loaded the same specs.

 

[rojodiablo]

I thought the 5.56 was designed by "NATO" (Military) so it was all 5.56 was loaded the same specs.

Well, while there ARE differences between true NATO ammo, and standard xm855 or xm193, the 5.56 IS loaded to the same specs.
( I will use Lake City made Federal ammo as an example for this, and leave out the dozen or so other ammo that is out there that may wind up as NATO in another country)- The primary differences between say xm855 and NATO xm855 are the tests done. WHile all ammo is tested to some degree, the ammo labeled as NATO will be batch tested, and random lot tested, and the tests are pretty stringent. The criteria of the test would be not limited to.... but would include: Velocity. Waterproof testing. Accuracy testing. Bullet weight, and construction tests- visual, cutaway and destructive. Cycling tests would be done.
The xm855 you buy is the same stuff, minus the tests. Sometimes, you will actually wind up with ammo that will have a 'REJECT' on the box, and sometimes it will say something to the effect of 'Not for deployment/ Not for combat issue/ Range ammo only/ training ammo only'.
Understand that NONE of these mark ups means the ammo is anything less. If the .mil takes in a busload of xm855 for training (And they do) the extra tests of the ammo to qualify as true NATO ammo add some cost to the ammo. So, they save money by using the regular stuff in droves.

More importantly than worrying about whether your ammo is equal to true NATO ammo, worry that your rifle will sufficiently cycle the top 10 types of ammo you might wind up with in your ammo can itself.
It does no good whatsoever to have a rifle that will not function flawlessly with the 'cheaper' ammo......... when all you can get is the cheap stuff. Or, the cost of the 'good stuff' is simply too much to bear.

 

[riderrick65]

Ok thnx every one for the great response, this answers my question to a T. I had just purchased 200 rds. of Independence 5.56 55gr FMJ XM1931 and wanted to make sure I had the right ammo.

 

[Monte C]

I'm glad you asked I got the same ammo at Cabelas last week and was wondering the same.

 

[TunaFisherman]

If your rifle is marked 5.56 (chambered for 5.56) you can also shoot .223.
But if your rifle is marked .223 DO NOT SHOOT 5.56 thru it!

 

[Mr. P]

good information -- I'm glad I check in here

Mr. P

 

[garyd54]

where is it marked on the weapon, I don't see it anywhere unless it's under the forend hand guard

 

[oneyeopn]

it depends upon the brand. S&W's are marked on top of the barrel, forward of the gas block. The Colts I have seen are the same just further out.

 

[Desert Five-0]

Go off the barrel marking. On my AR, it it under the hand guard. Do not go off what it says on the lower receiver since a 5.56 lower could be mounted to a .223 upper. Should not be different on a factory made rifle.

 

[oneyeopn]

My Sports dont have a caliber marked on the lower, I didnt think any of the S&W M&P15's have a caliber on the lower.