Fireforming 223 AI with 223 vs 5.56

[Ozshot]

Hi all just a quick one, I have just changed from military 5.56 once fired to 223 WCC and military headstamp cases (Australian) once fired. Should I expect much difference in loads by using the 223 cases? And lifetime of the military and Winchester 223 in AI vs the 5.56 military stuff?

 

[Oso]

Based on your thread title and comment, I'm not quite sure of exactly what your question. I'll take a stab at it...

The concern for forming 223AI is making certain you get a crush fit at the shoulder. Most factory ammo, 5.56 and some .223, are intentionally formed with short head spacing (shoulder is set back short of SAAMI Spec) to ensure reliable feeding/extraction through an AR15 or similar military rifle. From my experience this means that if your rifle chamber is set to traditional .223AI length then there will be a lot of factory ammo that will not ever "crush fit". For this reason it has become standard practice by gunsmiths to shorten the chamber by a few thousands in order to get a crush fit with factory ammo.

In theory 5.56 cases have thicker case walls and head/web. As a result, .223 cases should result in slightly more case capacity. However, this all depends upon the manufacturer the case. There is a lot of variation between headstamps so just test/assess your particular cases that you plan to use.

Since you are using once-fired and some of it is military then just check cases (after re-sizing) with case gauge to ensure no issue with swelling in the case head. The biggest risk for case life on 223AI is case head separation during the initial case forming. I have bought factory .223 ammo that was manufactured with headspacing as short as 0.015" from spec. If a case looks "Iffy" then toss it. Otherwise, normal wear and tear.

 

[Bill K]

Both will work just fine in fire forming to 23ai. I use both all the time. The main difference between them is the military 5.56 brass is loaded to a higher pressure and the rifles for their use have a longer lead to handle the pressure.
That is why the caution to not shoot 5.56 in the shorter lead in a standard 223 Rem chamber.

 

[RegionRat]

The above advice, plus always check the case web thickness and internal volume if you are concerned with matching up brass and recipes to the first order.

Any change is a change when it comes to state of the art performance, but the first order issue in this context is to match the case internal designs to make sure you are at least in the same ball park when using a load recipe.

At some point, you may encounter a difference in the internal design down at the bottom where the web thickness is thinner and creates a larger internal volume. Those types of examples are not worth your time in terms of fireforming. About all those are good for is plinking loads that will be discarded since the primer pockets will loosen up so quickly that fireforming them isn't worth your effort.

Check the web thickness by plunging the tail stock of you calipers down inside the cases and compare the difference. When you have the thin web, it is fairly easy to tell.

As far as any brass change makes a difference to you? Only a test will tell.

Inside of 300 yards it should be fairly forgiving. As I recall, you were doing headshots on roos? Your testing will be the bottom line.

Best to try and match cases in big batches to avoid extra testing and load tuning, but these days I am completely sympathetic to "use what ya got" issues.

 

[jepp2]

And lifetime of the military and Winchester 223 in AI vs the 5.56 military stuff?

AI case life, if properly sized, should be much longer than 223. I ran a case life test in my AR. Just wanted to see how many loadings I could get, and what would cause me to retire them. Kind of a worst case scenario since I was setting the shoulder back more for my AR than I would for a bolt gun. Shortest case life lasted 24 loadings, longest lasted 37. And they basically all failed due to gouges in the case neck from contacting the barrel extension locking lugs during ejection. I now stone the two offending lug corners to eliminate the issue.

 

[Ozshot]

The above advice, plus always check the case web thickness and internal volume if you are concerned with matching up brass and recipes to the first order.

Any change is a change when it comes to state of the art performance, but the first order issue in this context is to match the case internal designs to make sure you are at least in the same ball park when using a load recipe.

At some point, you may encounter a difference in the internal design down at the bottom where the web thickness is thinner and creates a larger internal volume. Those types of examples are not worth your time in terms of fireforming. About all those are good for is plinking loads that will be discarded since the primer pockets will loosen up so quickly that fireforming them isn't worth your effort.

Check the web thickness by plunging the tail stock of you calipers down inside the cases and compare the difference. When you have the thin web, it is fairly easy to tell.

As far as any brass change makes a difference to you? Only a test will tell.

Inside of 300 yards it should be fairly forgiving. As I recall, you were doing headshots on roos? Your testing will be the bottom line.

Best to try and match cases in big batches to avoid extra testing and load tuning, but these days I am completely sympathetic to "use what ya got" issues.

Good recall!! Yes on Roos. Generally I fire form about 1000 cases then move to my everyday load, that way I probably end up losing 30-40% over 6-8 reloads and by that time the barrel is screwed and I punt the brass and start again with a new rifle( only running howa and cheaper then re barreling here) I’m shooting off a rest out the window of a vehicle so as you can imagine you want your load reasonably constant if you are trying to push out to 300 on a vehicle door rest whilst the truck is idling! I really appreciate the time you all have taken I didn’t realize how much I didn’t. Know about reloading for maximum accuracy, so much more too it then I have been doing and I do it for a job so I really need to gain as much knowledge as I can

 

[Ozshot]

AI case life, if properly sized, should be much longer than 223. I ran a case life test in my AR. Just wanted to see how many loadings I could get, and what would cause me to retire them. Kind of a worst case scenario since I was setting the shoulder back more for my AR than I would for a bolt gun. Shortest case life lasted 24 loadings, longest lasted 37. And they basically all failed due to gouges in the case neck from contacting the barrel extension locking lugs during ejection. I now stone the two offending lug corners to eliminate the issue.
View attachment 1299185

Wow that’s an insane amount of reloading!!! Why are you getting the scoring before fire
Forming?? It’s funny you have said this though because the only cases I have every wrecked has been split necks from the gouges in the neck like the picture!! Good to know what it’s from!

 

[JSH]

I myself prefer quality milsurp 5.56 brass.
I would advise to anneal to get a good forming on your first loading. You may end up with some rounded shoulders other wise.

 

[Delfuego]

Crimped 556 pockets suck. I don't have the tools or time to deal with it.