i found this email reply to a guy with a dpms rifle on another forum. what do you make of it? every bit of info i have ever seen say the exact opposite.
RE: Panther Bull Sweet Sixteen (Model: RFA2-B16)Monday, December 15, 2008 1:53 PM
From: “DPMS Firearms” <dpms@dpmsinc.com>Add sender to Contacts To: "XXXXXXXXXXXXXXXXXXXXXXXXX
I am glad to set the record straight. The barrels that are stamped .223 are exactly that, and officially 5.56 will fire through it. However you will see excessive throat and bore erosion. So eventually you will turn your .223 into a 5.56 anyway. We suggest that if you have a .223 that you only shoot .223 Rem ammo. If there are any further concerns please feel free to contact me.
There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.
The cartridge casings for both calibers have basically the same length and exterior dimensions.
The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the “Leade”. Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for. Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.
Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges. Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy. However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.
Wow, I can’t imagine DPMS saying this. Of course they will say crap like this. If they didn’t then their sales would be potentially impacted when more educated people don’t buy their crap.
I’m not sure why anyone bothers with .223 in a carbine anyway. I can see varmint hunters, and true target shooters using it but for carbines I don’t know why they aren’t all 5.56. The reamers can’t cost anymore.
From what I have read one of the differences between .223 Rem SAAMI spec barrels and 5.56 NATO barrels beyond the dimensions is the pressure as has been mentioned earlier. The pressures are measured differently for each standard. 5.56 NATO is measured at the throat while SAAMI is measured at the muzzle. The 5.56 NATO standard if measured as per SAAMI would be about 20,000 psi higher. So the NATO spec of approximately 58,000 psi is equivalent to a SAAMI measurement of 78,000psi. The requirement for SAAMI proof loads is 78,500psi so every round of 5.56 through a SAAMI spec barrel/chamber is roughly equivalent to firing a proof load. This is what can lead to blown primers and other overpressure maladies.
This is all based off of the information I have found on the T&E methods and standards, if any of my information is wrong please let me know.
SAAMI pressures are not measured at the muzzle (there would be little pressure to measure at that point.) They are measured at the mid-case position.
This statement is patently false. The military method of measurement at the case mouth differs from the SAAMI method of measurement at the mid-case position and to quote Jeff Hoffman of Black Hills, the two methods are “not directly comparable.”
I dont get it? everywhere I look it is labeled .223 Rem (5.56) how the hell can I get 5.56 and not .223? Or is it ok to run .223 in my 5.56 since the pressure is lower?
