curious on 5.56 and .223

[SHAWNthePATRIOT]

I've posted a crap load of post this week...im really trying to get all the help and knowledge i possibly can before i purchase my AR. The Colt LE6920MP with magpul furniture is what im going with. I had a really important question because im constantly hearing something different on the subject. The colt LE6920 says, chambered in 5.56. Now can the rifle shoot .223 as well. Im hearing they're completely different in some way. any help is much appreciated thanks...

SHAWNthePATRIOT

[Clem]

I've posted a crap load of post this week...im really trying to get all the help and knowledge i possibly can before i purchase my AR. The Colt LE6920MP with magpul furniture is what im going with. I had a really important question because im constantly hearing something different on the subject. The colt LE6920 says, chambered in 5.56. Now can the rifle shoot .223 as well. Im hearing they're completely different in some way. any help is much appreciated thanks...

SHAWNthePATRIOT

The short answer is:
You can shoot .223 out of a 5.56 chamber.
You cannot shoot 5.56 out of a .223 chamber.
5.56 ammo has higher pressure, and the .223 chamber will not be able to handle it.

[AKDoug]

There is a shit pile of information on the subject if you search.

Short answer: You can fire a .223 out of a 5.56 chamber with no problems. The problem comes with some guns not cycling properly with .223 ammunition because the gas pressures are not right since they are set up for the higher pressure 5.56 round.

That said, my Daniel Defense runs on cheap UMC .223 just fine and I bet the Colt will too.

[OkieOutlaw]

I can quarantee that your new 6920 will cycle .223 flawlessly. Mine has at least. I have shot a wide variety of .223 ammo from various makers without a single hiccup. No to mention my handloads that use 20.3 gr. of IMR 4198 powder for a quesstimated MV of approximately 2826fps which is well below .556 pressures and velocities, and funtion just fine out of my gun.

[MistWolf]

The short answer is:
You can shoot .223 out of a 5.56 chamber.
You cannot shoot 5.56 out of a .223 chamber.
5.56 ammo has higher pressure, and the .223 chamber will not be able to handle it.

5.56 ammo does generate a little more pressure, but that's not why it should not be fired in a SAAMI spec chamber.

223 Remington ammo is made to generate full pressure in a SAAMI 223 Remington chamber which has a shorter throat. 5.56 ammo is made to generate full pressure in the 5.56 chamber which has a longer throat.

223 ammo made to fit the shorter throat of the SAAMI chamber loaded to the same pressure as the 5.56 ammo is loaded to, will be safe to fire in a SAAMI chamber. It will be a bit higher than SAAMI pressures but still well within safe limits of the brass and barrel.

Where the trouble starts is when shooting 5.56 ammo in SAAMI chambers with short throats. The shorter throat will cause the pressure of 5.56 ammo to be much much higher than it would be if shot in a 5.56 chamber.

223 Remington ammo loses performance when fired in a 5.56 chamber because the throat is long and does not allow 223 ammo to reach it's full pressure

[polymorpheous]

I've posted a crap load of post this week...

Post less, read more.
The information you seek is there.
Look for it.

[GRWolverineFan]

http://vuurwapenblog.com/2012/06/23/hard-data-on-5-56-vs-223-chamber-pressures/

http://www.luckygunner.com/labs/5-56-vs-223/

[wrecks30]

99% of what i shoot is .223 from my M&P. I dont even look at 5.56 unless I get a deal on it.