.223 to 5.56

Discussion about 5.56mm ARs

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rlandry6
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.223 to 5.56

Post by rlandry6 » Tue Sep 18, 2018 10:01 pm

My latest build is a DPMS upper chambered for 223 REM. Can this chamber be reamed to allow me to shoot 5.56? My other AR is a 5.56 and it would be great to be able to run the same loads in each rifle.
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Re: .223 to 5.56

Post by Omega » Wed Sep 19, 2018 12:13 am

rlandry6 wrote:My latest build is a DPMS upper chambered for 223 REM. Can this chamber be reamed to allow me to shoot 5.56? My other AR is a 5.56 and it would be great to be able to run the same loads in each rifle.
Just shoot 223 in both, problem solved. If you buy MILSURP 5.56, just shoot it in the 5.56 not the 223, and if you reload stay with the 223 pressures and you'll be fine.
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Re: .223 to 5.56

Post by rlandry6 » Wed Sep 19, 2018 7:20 am

I'm aware of that. Thanks for the response, however, that wasn't the question I asked.
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Re: .223 to 5.56

Post by Flatliner » Wed Sep 19, 2018 8:33 am

While there are always 'caveats' that an internet mall ninja will be sure to point out, the direct answer to your question is yes. A reputable gunsmith should be able to assist you. Here is the link to a company I found with a quick google search that will do it for $30.

https://adcofirearms.com/shop/gunsmithi ... amber-556/

I have no experience with them so I can't vouch for their quality, turn around time etc, just wanted to give you an idea what you should expect to have to pay.

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Re: .223 to 5.56

Post by dellet » Wed Sep 19, 2018 8:53 am

Just a thought.

First find out what length the same bullet jams in both chambers. First in the 556 and than how much you have to shorten it to fit the 223.

Then compare fired cases. The base and shoulder numbers may surprise you, or not.

It would not surprise me to find that the 223 chamber is cut a bit on the long side, and the two chambers might be much closer than you think. If that’s the case it might be worth casting both chambers for actual comparison.

The throat length is the big difference between the two chambers, but true NATO chambers will be slightly larger diameter. Part of the reason people have trouble sizing military brass to convert.

The reason for going through this is there have been more than one rumor of commercial 223 barrels being cut closer to 556 to keep from having issues with people using the wrong ammo.
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Re: .223 to 5.56

Post by Flatliner » Wed Sep 19, 2018 9:30 am

dellet wrote:Just a thought.

First find out what length the same bullet jams in both chambers. First in the 556 and than how much you have to shorten it to fit the 223.

Then compare fired cases. The base and shoulder numbers may surprise you, or not.

It would not surprise me to find that the 223 chamber is cut a bit on the long side, and the two chambers might be much closer than you think. If that’s the case it might be worth casting both chambers for actual comparison.

The throat length is the big difference between the two chambers, but true NATO chambers will be slightly larger diameter. Part of the reason people have trouble sizing military brass to convert.

The reason for going through this is there have been more than one rumor of commercial 223 barrels being cut closer to 556 to keep from having issues with people using the wrong ammo.
VERY solid advice

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Re: .223 to 5.56

Post by Omega » Wed Sep 19, 2018 9:32 am

If you really want to, I don't see a reason why you couldn't, but my answer above still stands. I've shot .223 and 5.56 interchangeably for years with no regard to what was actually stamped on the barrel as far as .223 or 5.56. And, if you really come down to it 223 is SAAMI while 5.56 is not, so all data for reloading is probably for .223 not 5.56. Pressure is the primary reason why it is cautioned not to shoot 5.56 out of .223, but I've never heard of any serious issues happening, and with the internet, you'd think this would be reported far and wide if it was happening as is reported when a 300Blk is fired in a 223/5.56.

https://www.luckygunner.com/labs/5-56-vs-223/
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Re: .223 to 5.56

Post by Mike7.62 » Wed Sep 19, 2018 11:39 am

rlandry6 wrote:My latest build is a DPMS upper chambered for 223 REM. Can this chamber be reamed to allow me to shoot 5.56? My other AR is a 5.56 and it would be great to be able to run the same loads in each rifle.
The only problem that I see in doing so would be if the chamber is chrome plated. Two reasons, one being that chrome is harder to cut through, and damage to the reamer might occur, and the 'smith may not want to do this; the second is that by reaming and removing the plating you are eliminating one of the best features for reliability under harsh conditions. Of course if this is just a plinker that won't be used in this environment, or for serious social use, then have at it.

I will say that the advice given by Dellet is very good, and knowing your chamber dimensions is the first step prior to cutting anything.

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Re: .223 to 5.56

Post by drayks » Wed Dec 23, 2020 12:38 pm

Resurrecting an old post. In regards to converting a .223REM chamber to 5.56NATO chamber---Ned Christiansen of MICHIGUNS sells a Neck and Throat Reamer that does NOT change HEADSPACE, but cuts neck and leade if they are .223 REM to 5.56NATO. Will work on steel, SS and used chrome chambers, but not on MELONITE. Total cost is $260. I would like to purchase one, but am looking to see if others are interested in throating or checking their existing chamber dimensions. I have an old SAKO that I would like to convert, but can't justify a one time use and check of my 5.56 ARs. Let me know if you are interested in a rental if I make the purchase. Read up on Ned's site if there are any other questions. drayks

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