5.56x45mm Factory Ammunition

[DadSmith]

I wonder if all factory ammunition marked as 5.56x45mm actually load it to SAAMI spec pressure at around 62,000 psi? Or is mostly loaded to 223 Remington spec around 55,000 psi?

I've shot a lot of so called 5.56x45 and it doesn't seem to be all that hot. More like 223 Remington especially velocity wise.

 

[JEBland]

I was under the impression that it was more about chamber dimensions & bullet varieties causing pressure spikes than those readings for what makes 5.56 unsafe in a .223.

https://ultimatereloader.com/2018/08/05/223-vs-5-56-facts-and-myths/

Something I haven't read completely:

https://ammunitionstore.com/content/5.56%C3%9745mm%20NATO.pdf

 

[DadSmith]

I was under the impression that it was more about chamber dimensions & bullet varieties causing pressure spikes than those readings for what makes 5.56 unsafe in a .223.

https://ultimatereloader.com/2018/08/05/223-vs-5-56-facts-and-myths/

Something I haven't read completely:

https://ammunitionstore.com/content/5.56%C3%9745mm%20NATO.pdf

Not what I'm says. I know you should not shoot 5.56x45 in a 223 Remington because of the tighter chamber in the 223 Remington.
That is good information you posted though.

I mean 5.56x45 is not loaded up to full potential. I load 5.56x45 at home and 223 Remington. So for the 75gr Hornady HPBT Match for 5.56x45 I load 26.4gr CFE 223, but for my 223 Remington I load 24.7gr. Both are about maximum loads for each. I've fired my 223 load in my AR-15 and the 5.56x45 load and there is a difference in velocity and report. The 223 Remington avg velocity is around 2466 fps the 5.56x45 average is 2682 fps. Those are my reloads.

Now you take factory loaded 5.56x45 55gr M193 vs a factory 55gr 223 Remington and many times there isn't much difference between them velocity wise. There should be at least 150-200 fps gain for 5.56x45 ammunition over 223 Remington of the same weight bullet. I find that isn't so.

So my question. Are some factory 5.56x45 loading to 223 Remington pressure and velocity instead of the actual 5.56x45mm pressure and velocity?

 

[nipprdog]

Now you take factory loaded 5.56x45 55gr M193 vs a factory 55gr 223 Remington and many times there isn't much difference between them velocity wise. There should be at least 150-200 fps gain for 5.56x45 ammunition over 223 Remington of the same weight bullet. I find that isn't so.

A few months ago there was a guy at my local range that had a chronograph set up. I fired a few rounds of Norma .223 55gr through it. Norma states on there site that it should be 3240 fps. Average was 2830 in my 16" ruger bolt action. Fired a few rounds of Federal XM193 55gr and the average was 3140.

 

[DadSmith]

A few months ago there was a guy at my local range that had a chronograph set up. I fired a few rounds of Norma .223 55gr through it. Norma states on there site that it should be 3240 fps. Average was 2830 in my 16" ruger bolt action. Fired a few rounds of Federal XM193 55gr and the average was 3140.

I finally found my black book of load data.
The 223 Remington ammo I was using.
Hornady Superformance 55gr GMX vs Federal XM193 55gr in my AR-15 16" barrel.

https://www.hornady.com/ammunition/rifle/223-rem-55-gr-gmx-superformance#!/#additional

Now that I look at it. This was supposed to give higher velocity at low pressure. So I'd say it did just that.

Now I'm going to have to try a bunch of different brands 223 Remington vs 5.56x45.
55gr and 62gr to see what happens.

 

[BugI02]

A few months ago there was a guy at my local range that had a chronograph set up. I fired a few rounds of Norma .223 55gr through it. Norma states on there site that it should be 3240 fps. Average was 2830 in my 16" ruger bolt action. Fired a few rounds of Federal XM193 55gr and the average was 3140.

Were you compensating for any difference in length of the test barrel they determined their speeds from?

 

[BugI02]

I finally found my black book of load data.
The 223 Remington ammo I was using.
Hornady Superformance 55gr GMX vs Federal XM193 55gr in my AR-15 16" barrel.

https://www.hornady.com/ammunition/rifle/223-rem-55-gr-gmx-superformance#!/#additional

Now that I look at it. This was supposed to give higher velocity at low pressure. So I'd say it did just that.

Now I'm going to have to try a bunch of different brands 223 Remington vs 5.56x45.
55gr and 62gr to see what happens.

As best I could find, the test barrel for the superformance ammo was 20" and the ammo's claim to fame is longer duration of peak pressure, so shooting it out of a shorter barrel (if you were) should be expected to give you lower velocities