Home Forums Hunting & Shooting AR and Tactical Rifles 223-5.6 Difference?

I have several prints and only see freebore as the difference.

The pressure is read differently, I've read, with the 5.56 taken further forward. If I can remember where I saw it, I can elaborate a bit if it would help.

Basic rule is supposedly .223 is safe in 5.56 chamber, but not always conversely because of that throating difference. The Wilde chamber is a compromise.

Generally that's what I've read. Throat dimensions for the 5.56 and the pressures. 223 rem 55k psi. 5.56mm 60 something psi. It's on Ramshot's load data.

5.56 pressure is 62,350 psi as per Ramshot load data. http://www.accuratepowder.com/wp-content/uploads/2018/11/WPHandloading-Guide-7.0-Web-REV.pdf

Freebore is the big difference, but throat diameter is usually a little larger on the 5.56 spec, as well as slightly looser neck and chamber dimensions. (there are exceptions, "usually" being the key word). The Wylde chamber combines the long freebore (enabling hotter loads, much like Weatherby Magnum chambers) with the tighter throat diameter for better accuracy.

I guess it really doesn't matter as I'm doing a bolt rifle I guess.

it's not about the type of action, it's about the bullets you want to use. The old 223 Rem chamber is more suited to light varmint bullets, while the Wylde and 5.56 chambers accommodate heavier bullets. In my experience the Wylde chamber shoots the light varmint bullets very well too and can be loaded to a bit higher velocity because of the freebore.

For building my own barrel as you will, the choice for me would never be between a 223 Rem and 5.56 chamber, it'd be between 223 Rem and 223 Wylde, with my choice in most situations going to the Wylde. Your choice may differ.

Of course there are a number of other match chambers one could choose from as well.

Maybe this is a good time to bring up something I have been puzzling over for quite some time. I've looked over a lot of stuff I've been able to locate on-line regarding the differences between 5.56 and .223 Remington. Some of my observations:

- SAAMI limits .223 Rem to 55000 psi

- the US military utilizes a standard they call SCATP, which includes pressure testing identical to the SAAMI method

- the highest published SCATP pressure figure I have found for 5.56 in US Army documents was a touch over 58000 psi, IIRC

My conclusion for the moment is that the highest pressure American 5.56 ammo would register a little over 58000 psi ala SAAMI. I know there is or was a new M855A1 round loaded hot, but as far as I know the pressure spec was never made public. Based on this, I would assume that an AR15 with 5.56 chamber can handle 58000 [SAAMI] psi, no sweat. On the other hand...

- NATO follows a standard they call EPVAT for 5.56 ammo testing

- EPVAT allows pressures of about 62000 psi

- EPVAT pressure measurement is similar to CIP methods, but not identical

- the CIP pressure limit for .223 Remington seems to be about 62000 psi also

Now...maybe my assumption that European .223 Remington ammo would register 55000 psi if tested to SAAMI methods is faulty. I kinda doubt it though. But here's the problem as I see it: published 5.56 data in American loading manuals lists pressures up to 62000 psi. Comparing it to .223 data in the same manual shows the 5.56 data is considerably hotter, so I would assume that the 5.56 data as published would actually mean pressures measured via SAAMI methods (but I never see this specified, IIRC). The thing is, if they're publishing data that would yield 62000 psi when measure ala SAAMI, what would CIP methods show on that same ammo? I think it would be waaaay over 62000 psi.

The whole thing does not smell right to me. Where is the error in my perspective? What am I not seeing?

Fortunately I have several reamers available and 2 barrels, an 8 twist and a 12 twist. I will be using a Stiller TAC 30 receiver that I picked up at the Shilen Swap Meet. I will set up the 12T for 52-60 grain bullets and 77grn in the 8 twist.
Thanks for the help.

Dimensions from several sources, according to their reamers.

MM

It'll only come as a "surprise" to Texans,that a single RPM and a smidge sense tossed at freebore...will simply do it all and then some.

Someone ask her how she's gonna feed it and at what COAL,because THAT will be just as fhuqking FUNNY.

Hint.................

The original military load for the M193 was very hot, either 28 or 28.5gr of WC844 (aka H335)

YIKES! That would definitely be a hot load. I wonder what the thinking was behind that. Can you provide a link or reference for that info? I'd like to add it to my files if possible.

I wish I had bookmarked all the documents I found and looked at...I did download them, but I don't know how I'd make them available to any interested.

MIL-C-63989C (AR) AMENDMENT 4, 30 January 2001 shows the following change to the previous amendment pertaining to M193:

"3.7 Chamber pressure. The average chamber pressure of the sample cartridges, conditioned at 70 degrees plus or minus 2 degrees F, shall not exceed 58,700 psi. Neither the chamber pressure of an individual sample test cartridge nor the average chamber pressure plus three standard deviations of chamber pressure shall not exceed 64,700 psi."

MIL-C-70460A (AR) AMENDMENT 2, 15 October 1999 shows an almost identical revision for the M855 round.

That is the highest average chamber pressure figure I have ever located in any American military document. I'm not saying there ISN'T a pressure revision document, but if there is I am not aware of it. If it exists, I'd like a copy of it.

I would never use a Wylde in a bolt gun.

I would use the tighter .223 Match or at the loosest, the CLE.

What reamers do you have? Are these going to be mag fed?

TM 43-0001-27
ARMY AMMUNITION DATA SHEETS
SMALL CALIBER AMMUNITION
FSC 1305

Chapter 10, page 3.

http://pdf.textfiles.com/manuals/MILITARY/united_states_army_tm_43-0001-27%20-%2029_april_1994.pdf


Yea, it's hot.

I've loaded 28.5gr of Mil Surpluss WC844 behind 50-55gr bullets before.
In a 5.56 change pressures are fine with Noslers BT, CC etc, not so much with Hornady Vmax....

And don't accidentally drop one into a semi-auto .223 chamber, unless you like picking primers out of your trigger group.

Thanks AS...I do already have that document. They do show a 28.5 grain charge, but they also show a pressure of 52000 psi.

Butch, I hope you are not feeling like I've derailed your thread. I kinda suspect you were thinking more along the lines of chambering reamers when you posted your question, but once the pressure aspect was brought into play I just had to ask my own question. Maybe it should have its own thread, but to be honest I hate to think of how many pissing contests will start if I do post a new thread. We're kinda flying under the radar here, I think.

Although I provide a link to the 1994 version of the TM, the data sheet's the same in the 1967 version. Knowing how much we've learned since 1967, and having loaded it with actual Mil surplus powder (not the commercial equivalent), and comparing it with commercial load data, I'm pretty skeptical of the 52k PSI number.

I'm enjoying it! You know, you kinda pick the fruit out of the chaff.

MM,
What really amazed me, is just how small the differences really are, and how much discussion they generate.

Couple thousands there, couple 10's of thousands there.....How many uses does it take for a reamer to loose a couple thousands, or how many rounds until you .223 chambers wore out to 5.56 dimensions?