Rifle caliber 5.56x45mm question


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Gouranga
July 20, 2010, 12:10 PM
alright, I have finally reached a level of confusion here and i need y'all to set me straight. I get VERY confused when I get to smaller calibers (I usually live either at .22lr or in .3 and above).

Assume a semi auto rifle takes 5.56x45mm, is that equivalent with any other caliber. I have had folks tell me that caliber is the same thing as a 223. But here is what bugs me about that:
Look at the DPMS catalog: http://www.dpmsinc.com/firearms/category.aspx?id=4

Those are their rifles for 5.56x45mm, they have an entirely different section for 223. What gives? Are they interchangeable always, sometimes, different names for the same thing? I have heard so much conflicting info from stores where I asked my head hurts.

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RhinoDefense
July 20, 2010, 12:19 PM
The 5.56x45 NATO is a chamber spec for NATO countries.

The .223 Remington is a cartridge spec for SAAMI members.

5.56x45 NATO is very similar to the .223 Remington, but the NATO chamber spec has a longer throat (portion of rifling that's cut away to form the forward part of the chamber).

You can safely fire .223 in a 5.56 chamber, but not conversely.

GRIZ22
July 20, 2010, 12:21 PM
223 and 5.56 are not the same although external dimensions are. It has to do with the chambering. Firing a 5.56 in a 223 could be dangerous resulting in an overpressure situation. You can fire 223s forever in a 5.56 with no problem. You can have a 223 chambered to 5.56.

AR15.com has a good article on this.

Gouranga
July 20, 2010, 01:08 PM
From what I have read though "they" say that a 223 fired out a 5.56 will cost you some accuracy? This true? If so, how severe a loss is it?

briansmithwins
July 20, 2010, 02:03 PM
If you're worried about accuracy in 1/10ths of MOA, be worried. Otherwise, not so much of a problem. BSW

rcmodel
July 20, 2010, 02:42 PM
"they" say that a 223 fired out a 5.56 will cost you some accuracy? This true?I would say just the reverse is true.

Some of the most accurate ammo made is .223 Rem Match & Varmint ammo.

Firing it in a 5.56 NATO chambered rifle will most assuredly improve the rifles accuracy over any & all 5.56 NATO military grade ammo.

rc

Kwanger
July 20, 2010, 03:37 PM
I agree with rc. The variables in the ammo itself are far more of a factor than any theoretical accuracy disadvantage from using 223 in 5.56. Top flight match 223 is better than any 5.56.

Gouranga
July 20, 2010, 03:58 PM
So "they" could be wrong...imagine that, lol.

I agree with rc. The variables in the ammo itself are far more of a factor than any theoretical accuracy disadvantage from using 223 in 5.56. Top flight match 223 is better than any 5.56.

So what you are saying...I should spend hours at the range trying out as much ammo as i can. Sounds like a horrible fate, lol. ;) Thanks guys. Y'all have been a great help.

rcmodel
July 20, 2010, 04:01 PM
You can take it too the bank that FMJ military type ammo will not shoot anywhere near as accurately as .223 Match or Varmint ammo with hollow point or plastic tip bullets.

You don't even need to bother testing it to find out.

rc

Gouranga
July 20, 2010, 06:53 PM
You don't even need to bother testing it to find out.

I appreciate it but where it the fun in that? LOL j/k. I do appreciate the info guys. It is funny, these calibers in that area, I simply have ignored until now. I am picking up a DPMS Classic 16 in 5.56x45 for just fun shooting, and I realized I know jack about that caliber range.

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