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.223 rem to 5.56 Nato

This is a discussion on .223 rem to 5.56 Nato within the Reloading forums, part of the Firearm Forum category; PaddyD55, I don't know where you got your information but most of it is totally bogus. The difference in case capacity between a civilian 223 ...


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Old November 22nd, 2016, 08:46 AM   #31
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PaddyD55, I don't know where you got your information but most of it is totally bogus. The difference in case capacity between a civilian 223 Rem and a NATO 5.56 is about 1% less in a NATO case. Yes, this will increase chamber pressure but not by more than 1k psi. The rest of your post has absolutely no merit .... just a bunch of crap made up for the Internet.

Just for the record .... Military M-16s and AR-15s first had exactly the same chamber as a civilian 223 Rem. Later DoD found accuracy after about 250 yards really sucked with the 55gr FMJs so they designed a new slightly heavier bullet with a much higher ballistic coefficient. This new 62gr bullet maintained decent accuracy out to 500 yards in a 20" barreled M-16 with a 1:9 twist rate. However to get the ballistic coefficient higher, the ogive had to be moved forward about .040". The ogive is the place on the bullet where the diameter is the same as the distance between lands in the bore .... or about .219" in a .224" bore. If the ogive on the bullet is pressed against the lands, chamber pressure will elevate so a decision was made many years ago to increase the M-16/AR-15 chamber leade by .040". The OAL of the old 55gr USGI and newer 62gr NATO cartridges are exactly the same (2.260").

Chamber pressure difference in a 223 Rem and a 5.56 NATO is grossly overstated. First of all, there are three popular types of pressure testing .... SAAMI for US made civilian cartridges, CIP for European made civilian cartridges, and EPVAT for US military and NATO cartridges. EPVAT and CIP pressure testing is nearly identical. SAAMI pressure tests are conducted at mid-body of the cartridge where max pressure is rated at 55,000 psi. 5.56 NATO cartridges (EPVAT) are pressure tested at the case mouth where the max pressure is rated at 62,366 psi. If a 5.56 NATO cartridge was tested the same way as a SAAMI cartridge, chamber pressure would be nearly identical .... about 1k psi higher in a 5.56 NATO due to the slightly smaller case capacity. So ... the myth about a 5.56 having much higher chamber pressure is just a difference in measuring techniques .... not an actual pressure difference. Back to reinforce the previous paragraph .... if 5.56 NATO ammo is fired in a 223 Rem chamber, chamber pressure will indeed increase ... possibly enough to damage the rifle. This is strictly because the ogive is .040" farther forward .... not because the 5.56 NATO cartridge is loaded hotter.

It's really too bad all this misinformation about 223 Rem versus 5.56 NATO has been spread throughout the Internet. People just don't know what is fact and what is fiction. A good example is in PaddyD55's post concerning "The military needed to downsize the ammunition for logistical purposes......" This is true but it relates to converting from the M-14 (7.62 NATO) rifle to the M-16 (5.56 NATO) rifle and has absolutely nothing to do with the 5.56 NATO cartridge itself. There is no such thing as a "power factor" ....only a standard that other NATO countries are supposed to adhere to. "Yaw" doesn't happen until the bullet is traveling down range and is totally unrelated to chambers. So much garbage and so little facts.



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Old April 15th, 2017, 01:09 PM   #32
 
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Reloaded brass 223 & Nato

Ok. I can only imagine how many of you guys are going to slap your forehead or totally ignore me.. I've to understand , but keep falling short! I have a Rem 700 PS 223 I can reload any brass I want, non-Nato or Nato brass with a 64gr Nosler BSB on top of 25 grains of Varget and shoot sub 1" MOA at 100 yds consistently! I have a Ruger American 223 That WILL NOT CHAMBER the exact same round if it is loaded in Nato brass, But will chamber the non-Nato brass and shoot it 1" MOA all day.. WHY?? What is different? the COAL is exactly the same and the OAL is exactly the same. I've been reading as much as possible in my manuals and on line but can't see what I'm missing
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Old April 15th, 2017, 02:15 PM   #33
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28 points, What you are missing is a common issue with spent rifle cases .... especially 223 Rem/5.56 NATO cases. Some chambers are more generous than others and allow fire formed case heads to expand. Once the case head expands, chance are it will NOT chamber in another rifle. RCBS and Redding to the rescue. These companies (and maybe others) make small base dies that are designed to address your very issue. Once brass has been sized with a small base die, it will chamber easily in virtually any chamber 223 Rem or 5.56 NATO rifle. Here's a couple photos of a tool I made .... kind of a go - no go thing. If cases slide through the hole, they will chamber in most any 223 Rem / 5.56 NATO rifle. If cases do not slide through the hole, chances are they will not chamber in most other rifles but will probably chamber in the rifle they were fired from.

The first photo shows a case that is about .001" too fat and won't chamber properly in rifles with a tight chamber.



The second photo shows a factory case that will easily slide through the hole and will chamber in any 223 Rem or 5.56 NATO rifle.
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Old April 15th, 2017, 05:01 PM   #34
 
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Reloaded brass 223 & Nato

Iowegan, that go - no go gauge is a great idea. thank you for explaining the case expansion. So I have to get a small base die in order to use the Nato brass in my Ruger American if I understand you correctly because the chamber in my Ruger is much tighter than the camber in my Rem 700 PS. And by the way this is all range brass I'm reloading.
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Old April 15th, 2017, 05:07 PM   #35
 
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Also I use a RCBS Competition Die set
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Old April 16th, 2017, 07:00 AM   #36
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28points, I had the very same issue only it was my Ruger AR556 that was so fussy. I bought a set of RCBS small base dies. I only needed the small base sizer die but couldn't find one so I ended up buying the 2-die set from Cabela's. What a world of difference!! I picked up a lot of once fired brass .... both 223 Rem and 5.56 NATO. Once it is sized with the small base die, the brass will work just fine in my Rem 700 and my Ruger AR556.
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Old April 16th, 2017, 08:36 AM   #37
 
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Reloaded brass 223 & Nato

Thank you again!! Huge help
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