Discussion in 'Small Stuff--22s, 20s, and 17s' started by wboggs, Nov 24, 2012.
Are these rounds interchangeable or do differences exist?
The cases are the same.The difference is the chamber.The 5.56 has a longer leade for different standards of ammo by makers.
No differance other than the chamber specs. Adam
The .223 Remington has a peak pressure of 50,000 psi while the 5.56 NATO has a peak pressure of 62,000 psi. Depending on the rifle and the lot of 5.56 NATO cartridges, the difference could be major. Also, as stated above, the throats are different. Military brass is heavier walled in order to handle the higher pressure of the 5.56 NATO cartridge. So, while the external dimensions of the two cases are identical, the internal dimensions are not the same and the pressure differences caused by mixing the cases can cause major problems. A safe load in a .223 Remington case may be unsafe in a 5.56 NATO case due to the smaller internal dimensions of the 5.56 NATO case. It is safe to shoot both .223 Remington and 5.56 NATO in a 5.56 NATO chamber but not the reverse. There are also a couple of proprietary chambers (e.g. the .223 Wylde used by Rock River) that can safely fire both cartridges
Here we go......
Cort I agree some with what you discribe of the two chambers, but this part above is very incorrect. I have done EXTENSIVE research on this and this is one of those gun writer wives tails that keeps getting past down time and time again. 308/7.62 yes but NOT THE 223/556. I have called and discussed this with one of the leading 223 manufactures.. Jeff Hoffman from Black Hills Ammo who Manufactures Varmint 223 ammo Match 223 ammo as well as Mk262 Combat 5.56mm Military ammo. The brass is NOT any thicker than commercial brass and in fact some commercial brass is thicker than some LC, IMI,and WCC brass. There is even a good Article right here about case volume if anyone would care to look at it. ( ill see if I can find the link)
I have to say this is my biggest pet peeve of this being passed around. So please bear with me, i can feel my face turn red and my blood pressure rise just thinking about it.
I bet there are alot of varmint hunters loading there reloads to the higher 60,000 psi chamber pressure as well. But your point is well taken non the less.
I have been getting infomation together to do a article on this very subject because Im tired of the dribble comming from our gun writers.
I see a huge difference between the Lapua brass that I have and I have over 1000 pcs from different lots and LC brass and I have over 1000 pcs of it, from two different years. I can not tell you the difference in thickness of the brass, but I can tell you that for the Lapua brass, I use a .250 bushing to size the neck in order to hold the bullet, with the LC brass it is a .246 bushing. This is on un-neck turned brass.
This is interesting. The story has been around forever so I took it for gospel. I only shoot brass that I purchase new and always work up my loads. Consequently, mixing brass is a non-issue and pressure is a non-issue also since I am looking for pressure signs as I go. I am sure there are folks running above the SAAMI pressure standard of 50,000 psi in their .223's. The difference in freebore is a concern since a jammed bullet generates higher pressure than a jumped bullet.
Randy - I wonder if your experience in neck sizing is universal or just Lapua brass versus military brass?
If I remember right, I was using a .248 bushing back in the day when I was getting R-P brass for free, I mean buckets of it. I don't remember ever using Winchester brass, so I can not say there. If I neck turned my Lapua brass, I was using a .250 bushing and then running them back over the expanding mandrel so that I would get .001 tension.
With the LC brass, It is a whole new ballgame because the brass walls in the necks are thinner.
I am going to have to get some 5.56 NATO and some commercial .223 Remington and cut the cases in half. It sounds as if the NATO brass has thinner necks than commercial. What are the case wall thicknesses of the two? It will also be interesting to see how much H2O each case holds after sizing.
If I can find several different brands, I will post what I measure.
I have already cut a bunch in half. Remington, LC 06, 09, 10, LAPUA NEW, WCC 09, winchester, IMI from about 1998, Hornady 11,
All part of the article I was putting together.... very slowely.
Going Back to the original post from Mr. Boggs before Randy and I got it off course on Brass case capacity and neck thickness.
The question is "can you interchange these loaded rounds" The safe answer is no. As Cort pointed out the MilSpec ammo is loaded to a higher pressure than the factory Varmint ammo from say Hornady, Federal, and Remington ect ect. If for instance you have a factory rifle with the Normal short throat and shoot some Milspec ammo you chance overpressure in the rifle. Because of the loose 5.56 chambers and more importantly the longer Freebore(Throat) allow that 5.56 ammo to shot safely in those chambers. Again like Cort correctly points out there is now a few manufactures creating there chambers to the wyled or also the 5.56 chamber so people can use the surplus ammo.
If you know what your chamber is then you could go forth with shooting the Surplus ammo in your rifle.
Hope this answers your question. And sorry to Highjack your thread.
Hope all is well and shoot straight.
The pressure myth started with the Army TM 43-0001-27 where ALL chamber pressures are listed in PSI with both the copper crusher and transducer method being used.
The military 5.56 has a longer throat for a more gradual buildup of chamber pressure to "REDUCE" bolt thrust under combat conditions, wet or oily chambers, wet bore etc.
The following listed pressures are actually equal to each other but are written differently because of the testing methods.
The following three pressures are the same pressure using diffrent testing methods.
SAAMI 52,000 cup (copper crusher)
SAAMI 55,000 psi (transducer)
European CIP 62,000 psi (transducer method at case mouth)
Cartridge Pressure Standards
I have a Savage .223 bolt action and a AR15, the Savage has a throat "LONGER" than my 5.56 AR15 and I can shoot both military and commercial safely in my Savage. The real problem lies with .223 rifles with a short throat and these rifles will have a higher peak pressure when firing military ammunition.
Please read below, and NOTE that only short throated .223 rifles will be a problem. (see pressure charts at the link below)
5.56 vs .223 â€“ What You Know May Be Wrong
Also note that military 5.56 cases are not thicker like the older 7.62 NATO and the 30-06 LC cases. By mil-spec all 5.56 ammunition MUST have brass that is harder in the base and mid way up the body of the case to function under combat conditions.
The case hardness problem dates back to the original M16 jamming problem in Viet Nam and was just one of the fixes.
Are the .223 and 5.56 NATO the same? The answer is yes and no, a military 5.56 cartridge fired in a long throated M16 develops the same pressure as a commercial .223 fired in a short throated rifle. BUT doing the reverse and firing a military 5.56 in a short throated commercial chamber will increase pressure 10,000 psi over the rated pressure of the .223.
Modern .223 chambers are throated long enough so that a company firearms Lawyer will fit inside the chamber and thus not cause any law suits.
Separate names with a comma.