5.45x45 vs .223 casings

n9096h · November 7, 2011, 06:03 PM

I know this is a worn out, beat up topic. Maybe you all can help clear my confusion on this. I understood that the nato case has thicker walls than commercial .223 cases do, yielding higher pressures for a given charge. What I don't understand is if they do have thicker walls, then why does the Lake City 5.45x45 mil spec brass I just purchased weigh roughly 6% less than the winchester .223 I have?

darkroommike · November 7, 2011, 07:17 PM

Not sure but do you mean the NATO 5.56x45mm cartridge, there is a Soviet 5.45x39mm which would weigh less than a .223.

jepp2 · November 7, 2011, 09:22 PM

Assuming you are talking about 5.56 military brass and comparing that with 223 commercial brass, while common guidance is that the military brass is thicker and you should reduce your starting loads according, the data doesn't necessarily support this.

By weighing your cartridge cases you are being prudent but the attached data shows some commercial is considerably heavier than any military included in the study.

steve4102 · November 8, 2011, 08:20 AM

Quote:

I understood that the nato case has thicker walls than commercial .223 cases do, yielding higher pressures for a given charge. What I don't understand is if they do have thicker walls, then why does the Lake City 5.45x45 mil spec brass I just purchased weigh roughly 6% less than the winchester .223 I have?

Because 5.56 brass is not thicker and does not have less case capacity than 223 brass. As you have found out with your own eyes.
This is a myth that has been around for years and will not die. It's based the the fact that 308 and 30-06 Military brass is thicker with less case capacity than civilian brass. Because it's true for the 308 and 30-06 many assume it is true in the 223.5.56 as well. It is not.

Here is an article by the experts at Sierra. Scroll down to "Brass Preparation"
http://www.exteriorballistics.com/re...sgunreload.cfm

Then there is this. Scroll down to "Case Weight vs Capacity"
http://www.6mmbr.com/223rem.html

Last one.

n9096h · November 8, 2011, 02:49 PM

Thanks for your technical expertise. I suspected as much! Didn't seem to make sense to me that if mil spec brass had thicker walls that they would weigh less than commercial .223 brass. So my next logical question is regarding the chamber pressure differences. What causes the difference? Or is it simply a difference in where they measure the pressure?

saands · November 8, 2011, 03:31 PM

Chamber pressures are different because they are loaded to different specs ... they are very similarly sized cases, but they are not the same.

The situation we have must be very similar to that which they had in the early 1900's with the 8x57 Mauser rounds ... same size and shape, but different loadings, why they didn't just amp up the spec on the 223 when the 5.56x45 was released is a mystery to me ... IIRC, at that point it would have been all bolt actions that could have handled the higher pressures without issue. Now there are way too many chamberings of 223 to make that a possibility.

Saands

chack · November 8, 2011, 05:33 PM

the pressure numbers are different because they're measured in different units.

saands · November 8, 2011, 05:50 PM

Quote:

the pressure numbers are different because they're measured in different units.

This is true, but it is only part of the truth ... not the whole truth. Even if you used the same units there would still be a difference because they are loaded to different pressure specs. The database in my version of QuickLoad (a program that models internal ballistics) lists the SAAMI pressure spec for .223 as 55,000 PSI and the NATO pressure spec for 5.56 as 62,366 psi ... same units, more than 10 percent higher for the NATO rounds.

Saands ...

davery25 · December 21, 2011, 05:39 PM

people assume because of the pressure rating differences. As the OP found out, theres no definitive increase in case volume, it was a myth carried forward by wikipedia (something that has only been amended recently).

Pressure is a very difficult and somewhat subjective thing to measure - CIP and SAAMI, including different proof houses within the two have very different methods of pressure testing. There's lots of variances including whether its a piezo or CUP sensor and where those sensors are actually placed.

The pressure rating differences come from a difference in specs. US milspec anything is a LOT more rigorous than SAAMI's specs so military chambers will withstand higher pressures than a SAAMI chamber. The brass however, generates the same standard deviation in pressures whether its milspec 5.56 or commercial 223.

243winxb · December 22, 2011, 10:01 AM

Factory ammo- Do NOT fire 5.56 Nato ammo in a rifle marked 223 rem. See SAAMI . Read this > http://www.accurateshooter.com/cartridge-guides/223rem/

November 7, 2011, 06:03 PM	#1
n9096h Junior Member Join Date: November 7, 2011 Posts: 2	5.45x45 vs .223 casings I know this is a worn out, beat up topic. Maybe you all can help clear my confusion on this. I understood that the nato case has thicker walls than commercial .223 cases do, yielding higher pressures for a given charge. What I don't understand is if they do have thicker walls, then why does the Lake City 5.45x45 mil spec brass I just purchased weigh roughly 6% less than the winchester .223 I have?

November 8, 2011, 02:49 PM	#5
n9096h Junior Member Join Date: November 7, 2011 Posts: 2	5.45x45 vx .223 Brass Thanks for your technical expertise. I suspected as much! Didn't seem to make sense to me that if mil spec brass had thicker walls that they would weigh less than commercial .223 brass. So my next logical question is regarding the chamber pressure differences. What causes the difference? Or is it simply a difference in where they measure the pressure?

December 22, 2011, 10:01 AM	#10
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	223 Remington vs. 5.56×45–Chambering and Throat Considerations Factory ammo- Do NOT fire 5.56 Nato ammo in a rifle marked 223 rem. See SAAMI . Read this > http://www.accurateshooter.com/cartridge-guides/223rem/

November 7, 2011, 07:17 PM	#2
darkroommike Senior Member Join Date: August 27, 2011 Location: western Iowa Posts: 205	Not sure but do you mean the NATO 5.56x45mm cartridge, there is a Soviet 5.45x39mm which would weigh less than a .223.

November 7, 2011, 09:22 PM	#3
jepp2 Senior Member Join Date: December 24, 2008 Location: Loveland, CO Posts: 1,476	Assuming you are talking about 5.56 military brass and comparing that with 223 commercial brass, while common guidance is that the military brass is thicker and you should reduce your starting loads according, the data doesn't necessarily support this. By weighing your cartridge cases you are being prudent but the attached data shows some commercial is considerably heavier than any military included in the study.

November 8, 2011, 03:31 PM	#6
saands Senior Member Join Date: November 14, 1999 Posts: 1,573	Chamber pressures are different because they are loaded to different specs ... they are very similarly sized cases, but they are not the same. The situation we have must be very similar to that which they had in the early 1900's with the 8x57 Mauser rounds ... same size and shape, but different loadings, why they didn't just amp up the spec on the 223 when the 5.56x45 was released is a mystery to me ... IIRC, at that point it would have been all bolt actions that could have handled the higher pressures without issue. Now there are way too many chamberings of 223 to make that a possibility. Saands

November 8, 2011, 05:33 PM	#7
chack Junior member Join Date: May 24, 2011 Location: dixie Posts: 477	the pressure numbers are different because they're measured in different units.

December 21, 2011, 05:39 PM	#9
davery25 Senior Member Join Date: October 4, 2011 Location: Australia Posts: 318	people assume because of the pressure rating differences. As the OP found out, theres no definitive increase in case volume, it was a myth carried forward by wikipedia (something that has only been amended recently). Pressure is a very difficult and somewhat subjective thing to measure - CIP and SAAMI, including different proof houses within the two have very different methods of pressure testing. There's lots of variances including whether its a piezo or CUP sensor and where those sensors are actually placed. The pressure rating differences come from a difference in specs. US milspec anything is a LOT more rigorous than SAAMI's specs so military chambers will withstand higher pressures than a SAAMI chamber. The brass however, generates the same standard deviation in pressures whether its milspec 5.56 or commercial 223.