resizing 5.56 brass for .223 chamber

Miata Mike · May 22, 2011, 11:13 PM

Am I correct in assuming that if I resize and trim 5.56 brass using .223 dies, it would be OK to use in say a bolt action rifle chambered in .223? Being military NATO spec brass I also assume the case capacity should be less and that I should not load hot.

I would not be buying any factory ammo, only my reloads.

I have a 55 grain FMJ round worked up using H335 and mixed brass that works very well in a 1:9 twist M&P15 which is obviously chambered as 5.56.

I am torn between buying something in the AR platform or a Savage bolt action rifle hence my questions.

medalguy · May 22, 2011, 11:50 PM

As far as I know, no one makes a 5.56mm die so your only choice in dies is .223. I reload only milsurp brass for an M-16, two AR15's, a Mini 14, and a NEF .223 single shot rifle. All loads are from the same set of dies.

Don't assume military brass is thicker than commercial. I've tried all kinds of brass and found considerable variances in all of them. Some mil is smaller than some commercial and some mil is larger than some commercial.

Volucris · May 22, 2011, 11:56 PM

AFAIK the M&P series AR15s are chambered in a 223 Wylde chamber which is meant to accomodate 223 Remington and 5.56 NATO safely.
Check this information link out:
http://ammo.ar15.com/ammo/project/hist_diff.html

Once you full length resize it there is little to no difference. Lake City 5.56 NATO brass is some of the most common out there and people readily resize it and use it in everything from benchrest bolt guns to their loose tolerance mil-spec barrels in M4 and M16 uppers.

You are correct in thinking case capacity will have some differences notable from commercial 223 brass to 5.56 surplus. As always, separate cases by make and headstamp and work up your loads. That's just standard fair for any caliber you're reloading. If you want it really uniform then sort brass by weight after an ultrasonic clean.

steve4102 · May 23, 2011, 07:19 AM

5.56 and 223 ammo share the same external dimensions, it's the rifle chambers that are a little different. As stated above, there are no 5.56 dies.
It is an Internet myth that 5.56 brass has less case capacity than 223 brass, in fact in most instances just the opposite is true.

http://www.6mmbr.com/223rem.html

Miata Mike · May 23, 2011, 08:24 AM

All excellent replies!

I found the last link a very good read and will read the others right now. From all I have read, I didn't think using resized military brass in a .223 chamber would be a problem, but I could not find clear answers.

bullspotter · May 23, 2011, 09:51 AM

resized mil brass is about all i use in my 223 bolt guns, No problems, but i did rework up my loads.

**Unclenick** · May 23, 2011, 12:23 PM

As stated earlier, the new brass has the same external dimensions. The same is true with .308 vs. 7.62 NATO. The .223 and .308 are just civilian versions. The NATO chambers in both cartridges are a little longer and have more freebore. Since peak pressure is dependent on how much space the powder has to burn in after the case has expanded to fill the chamber and the bullet has met the throat, the NATO chambers will normally get somewhat lower peak pressures than civilian chambers do when firing the same exact load, but the difference isn't big. I calculated 1,600 psi difference for one such combination, but I suppose it could get to 5% of peak in some extreme instances. Certainly not a gun buster.

Note that the difference in weight on the list from highest to lowest load in the list Steve4102 copied is only 1.2 grains of water capacity. Typically, the change in powder charge needed for constant pressure in two different capacity cases using the same powder and bullet, is equal to roughly the square root of the difference in water capacities. That means, for a 25 grain charge, something on the order of half a grain charge difference from the smallest to the largest case on the list. Not nothing, but also not a gun buster difference in most instances.

(Steve4102, you might want to read the board policy on posting copyrighted materials, here.)

chris in va · May 23, 2011, 09:30 PM

Quote:

AFAIK the M&P series AR15s are chambered in a 223 Wylde chamber

The new M&P Sport I bought says '5.56 NATO' on it.

Eagle0711 · May 23, 2011, 10:29 PM

It's my understanding that the chamber thru the neck is the same. The NATO chamber has about .154" of freebore to handle the higher NATO pressure.

Don't shoot NATO ammo in a 223 chamber, because it doesn't have the leade or freebore to handle the hotter NATO round. If it's marked NATO you can safely shoot either.

May 22, 2011, 11:13 PM	#1
Miata Mike Senior Member Join Date: May 22, 2010 Location: North East WI Posts: 418	resizing 5.56 brass for .223 chamber Am I correct in assuming that if I resize and trim 5.56 brass using .223 dies, it would be OK to use in say a bolt action rifle chambered in .223? Being military NATO spec brass I also assume the case capacity should be less and that I should not load hot. *I would not be buying any factory ammo, only my reloads.* I have a 55 grain FMJ round worked up using H335 and mixed brass that works very well in a 1:9 twist M&P15 which is obviously chambered as 5.56. I am torn between buying something in the AR platform or a Savage bolt action rifle hence my questions. Last edited by Miata Mike; May 24, 2011 at 05:04 AM. Reason: I would not be buying any factory ammo, only my reloads.

May 22, 2011, 11:56 PM	#3
Volucris Senior Member Join Date: January 30, 2009 Posts: 293	AFAIK the M&P series AR15s are chambered in a 223 Wylde chamber which is meant to accomodate 223 Remington and 5.56 NATO safely. Check this information link out: http://ammo.ar15.com/ammo/project/hist_diff.html Once you full length resize it there is little to no difference. Lake City 5.56 NATO brass is some of the most common out there and people readily resize it and use it in everything from benchrest bolt guns to their loose tolerance mil-spec barrels in M4 and M16 uppers. You are correct in thinking case capacity will have some differences notable from commercial 223 brass to 5.56 surplus. As always, separate cases by make and headstamp and work up your loads. That's just standard fair for any caliber you're reloading. If you want it really uniform then sort brass by weight after an ultrasonic clean. __________________ "From my cold, dead hands!" - Charlton Heston

May 23, 2011, 07:19 AM	#4
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	5.56 and 223 ammo share the same external dimensions, it's the rifle chambers that are a little different. As stated above, there are no 5.56 dies. It is an Internet myth that 5.56 brass has less case capacity than 223 brass, in fact in most instances just the opposite is true. http://www.6mmbr.com/223rem.html Last edited by steve4102; May 23, 2011 at 04:52 PM.

May 23, 2011, 12:23 PM	#7
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	As stated earlier, the new brass has the same external dimensions. The same is true with .308 vs. 7.62 NATO. The .223 and .308 are just civilian versions. The NATO chambers in both cartridges are a little longer and have more freebore. Since peak pressure is dependent on how much space the powder has to burn in after the case has expanded to fill the chamber and the bullet has met the throat, the NATO chambers will normally get somewhat lower peak pressures than civilian chambers do when firing the same exact load, but the difference isn't big. I calculated 1,600 psi difference for one such combination, but I suppose it could get to 5% of peak in some extreme instances. Certainly not a gun buster. Note that the difference in weight on the list from highest to lowest load in the list Steve4102 copied is only 1.2 grains of water capacity. Typically, the change in powder charge needed for constant pressure in two different capacity cases using the same powder and bullet, is equal to roughly the square root of the difference in water capacities. That means, for a 25 grain charge, something on the order of half a grain charge difference from the smallest to the largest case on the list. Not nothing, but also not a gun buster difference in most instances. (Steve4102, you might want to read the board policy on posting copyrighted materials, here.) __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 22, 2011, 11:50 PM	#2
medalguy Senior Member Join Date: August 31, 2009 Location: New Mexico Posts: 1,033	As far as I know, no one makes a 5.56mm die so your only choice in dies is .223. I reload only milsurp brass for an M-16, two AR15's, a Mini 14, and a NEF .223 single shot rifle. All loads are from the same set of dies. Don't assume military brass is thicker than commercial. I've tried all kinds of brass and found considerable variances in all of them. Some mil is smaller than some commercial and some mil is larger than some commercial.

May 23, 2011, 08:24 AM	#5
Miata Mike Senior Member Join Date: May 22, 2010 Location: North East WI Posts: 418	All excellent replies! I found the last link a very good read and will read the others right now. From all I have read, I didn't think using resized military brass in a .223 chamber would be a problem, but I could not find clear answers.

May 23, 2011, 09:51 AM	#6
bullspotter Senior Member Join Date: November 2, 2008 Location: Montana Posts: 308	resized mil brass is about all i use in my 223 bolt guns, No problems, but i did rework up my loads.

May 23, 2011, 10:29 PM	#9
Eagle0711 Senior Member Join Date: August 25, 2010 Posts: 782	It's my understanding that the chamber thru the neck is the same. The NATO chamber has about .154" of freebore to handle the higher NATO pressure. Don't shoot NATO ammo in a 223 chamber, because it doesn't have the leade or freebore to handle the hotter NATO round. If it's marked NATO you can safely shoot either.