Usually is, but not always.
As posted, it doesn't hurt to check the headpsace on the AR, but it is likely OK and the cases are just having the shoulders moved back too far.
.223 case failure
- Thread starter SuedePflow
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As posted, it doesn't hurt to check the headpsace on the AR, but it is likely OK and the cases are just having the shoulders moved back too far.
Most of you guys have mentioned things that do happen but you're misidentifying what you've heard. The evidence either isn't there to prove your assumptions or you can't tell what's going of from the pictures and the OP's information.
The Ammo
Without more specific info (overall length, trim to length, case volume, muzzle velocity, etc.) it's impossible to estimate the max pressure produced by your dad's ammo but it's highly probable that they are at the top end of the SAAMI max. I have several reloading manuals from different manufacturers and they all show that the max powder charge is around 27.4gr of CFE 223 under a 55gr FMJ but my Quickload software shows that this depends greatly upon the case volume and my records show that the case volume of most LC 5.56 brass is greater than most other commercial brass so your pressures will probably be lower in the LC brass than other commercial brass. Either way, I don't think that the load is the problem.
The Case Pictures
Incipient head separations due to overworked brass usually happens at a lower point on the case due to the brass not being supported by the chamber. Most people don't realize that there is a short section of the cartridge case that is not surrounded by the rifle chamber, this section is the thicker part of the case head. Brass cracks from being overworked (expanding upon firing and contracting during resizing) because it becomes hard and inflexible. Soft brass will not crack as quickly as hard brass, if Federal brass is softer then it doesn't really matter because all brass hardens as it is worked through the firing and resizing process. If soft brass caused cracking then all brass would crack the first time you fired it because all brass is it's softest at this point in time, it always becomes harder as you reuse it. Incipient head separations happen because there is a stress gradient at the point where thickened head section thins down to the case wall. This place where the brass thins is where the cracks happen - that's not where your brass cracked. Also, as the brass is stretched and compressed a ring is created inside the brass just the place where the brass thins, when the case cracks at this point you will see a taper on the edge of the crack, if there is not taper then the case simply failed due to being too hard and not being overworked.
Your brass cracked at a place much higher than a normal incipient head separation, normally this is cause by one of three things;
Others have mentioned that there are recorded issues with machine gun brass, that's absolutely true and it might be the cause of the problem. Most of the brass fired in the 249 machine guns have been stretched pretty hard and undergo a lot of stress when you resize them the first time, if your father complained about how hard it was to resize his used LC brass and/or he had to use a carbide and lubricant, or he had to resize the case twice before they held the proper dimension then I'd say he was using old machine gun brass and they will definitely fail faster than other brass. In some situations the manufacturer doesn't properly anneal the case when they make it. Cases are pressed out of disks of brass, the disks are drawn over mandrels several times and they are annealed (softened) in between. The military has adjusted their process over the years changing how many times and when they anneal the brass during the process. The more times you stop the drawing process to anneal the brass the more expensive it becomes to manufacture the brass, as a result LC brass is annealed only enough times to allow the brass to be fired once, they don't care about firing it more than that, the military doesn't reload their brass. The final annealing step only softens the case down to about where yours cracked.
So my opinion is that the brass is just overworked LC brass that gave up due to slightly hotter than normal loads. The crack doesn't look like a normal incipient crack, it is too flat and it has vertical cracks in some places, all that indicates a hardness problem. Additionally, the crack happened about where they stop annealing the brass during manufacture. And finally, since these loads have been used by your dad before I don't think that they are the problem. The only other possibility is that the chamber is rough or there is a ridge inside right about where the crack happened. I'd check the chamber for proper smoothness with no ridges or grooves inside, if whomever reamed the chamber did not clean the chips out properly then they could have created roughness in the chamber that is putting stress on the case and causing it to crack. If the chamber looks good than I'd say that the problem is the brass.
The Ammo
Without more specific info (overall length, trim to length, case volume, muzzle velocity, etc.) it's impossible to estimate the max pressure produced by your dad's ammo but it's highly probable that they are at the top end of the SAAMI max. I have several reloading manuals from different manufacturers and they all show that the max powder charge is around 27.4gr of CFE 223 under a 55gr FMJ but my Quickload software shows that this depends greatly upon the case volume and my records show that the case volume of most LC 5.56 brass is greater than most other commercial brass so your pressures will probably be lower in the LC brass than other commercial brass. Either way, I don't think that the load is the problem.
The Case Pictures
Incipient head separations due to overworked brass usually happens at a lower point on the case due to the brass not being supported by the chamber. Most people don't realize that there is a short section of the cartridge case that is not surrounded by the rifle chamber, this section is the thicker part of the case head. Brass cracks from being overworked (expanding upon firing and contracting during resizing) because it becomes hard and inflexible. Soft brass will not crack as quickly as hard brass, if Federal brass is softer then it doesn't really matter because all brass hardens as it is worked through the firing and resizing process. If soft brass caused cracking then all brass would crack the first time you fired it because all brass is it's softest at this point in time, it always becomes harder as you reuse it. Incipient head separations happen because there is a stress gradient at the point where thickened head section thins down to the case wall. This place where the brass thins is where the cracks happen - that's not where your brass cracked. Also, as the brass is stretched and compressed a ring is created inside the brass just the place where the brass thins, when the case cracks at this point you will see a taper on the edge of the crack, if there is not taper then the case simply failed due to being too hard and not being overworked.
Your brass cracked at a place much higher than a normal incipient head separation, normally this is cause by one of three things;
- Brass that was not annealed properly at the factory
- Ammo that was too hot
- Improper chamber/ case dimensions
Others have mentioned that there are recorded issues with machine gun brass, that's absolutely true and it might be the cause of the problem. Most of the brass fired in the 249 machine guns have been stretched pretty hard and undergo a lot of stress when you resize them the first time, if your father complained about how hard it was to resize his used LC brass and/or he had to use a carbide and lubricant, or he had to resize the case twice before they held the proper dimension then I'd say he was using old machine gun brass and they will definitely fail faster than other brass. In some situations the manufacturer doesn't properly anneal the case when they make it. Cases are pressed out of disks of brass, the disks are drawn over mandrels several times and they are annealed (softened) in between. The military has adjusted their process over the years changing how many times and when they anneal the brass during the process. The more times you stop the drawing process to anneal the brass the more expensive it becomes to manufacture the brass, as a result LC brass is annealed only enough times to allow the brass to be fired once, they don't care about firing it more than that, the military doesn't reload their brass. The final annealing step only softens the case down to about where yours cracked.
So my opinion is that the brass is just overworked LC brass that gave up due to slightly hotter than normal loads. The crack doesn't look like a normal incipient crack, it is too flat and it has vertical cracks in some places, all that indicates a hardness problem. Additionally, the crack happened about where they stop annealing the brass during manufacture. And finally, since these loads have been used by your dad before I don't think that they are the problem. The only other possibility is that the chamber is rough or there is a ridge inside right about where the crack happened. I'd check the chamber for proper smoothness with no ridges or grooves inside, if whomever reamed the chamber did not clean the chips out properly then they could have created roughness in the chamber that is putting stress on the case and causing it to crack. If the chamber looks good than I'd say that the problem is the brass.
^
"Your brass cracked at a place much higher than a normal incipient head separation, normally this is cause by one of three things;
"So I have a question:
Is this case failure possibly due to using current heavy 5.56 loadings in older, thinner .223 brass? That separation seems to be right where the brass supposedly gets thicker in the newer military brass."
Terry
:
"Your brass cracked at a place much higher than a normal incipient head separation, normally this is cause by one of three things;
- Brass that was not annealed properly at the factory
- Ammo that was too hot
- Improper chamber/ case dimensions"
"So I have a question:
Is this case failure possibly due to using current heavy 5.56 loadings in older, thinner .223 brass? That separation seems to be right where the brass supposedly gets thicker in the newer military brass."
Terry
:
SuedePflow
Member
These reloads were produced by my father, and fired by him from his rifle. And the bags that they were in were listed with the loading details.
Last edited:
SuedePflow
Member
Thanks for the replies, guys. I'll let my father read over this thread and we'll check the gun's chamber. We also plan to re-work his CFE223 loads using less powder. I'll run these through my chronograph as well just to see where they are at. As was mentioned, probably just a bad or overworked piece of brass.
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