Case near failure autopsy

[MarikinaMan]

I found this cleaning cases. These cases were once fired LC brass. They've been reloaded about 5 times for my pet load. Hornady 75gr in 224, with 25.7 gr of Accurate 2520.



The case seems plenty thick, and is doesnt look like it was worked too hard as I can't see signs that the brass was flowing through the firings. Only that the split may have been due to structural weakness that was there right after it was made. I duhno, just guessing

[highpower790]

Case hit the 1/2 round portion of the ejection port on extraction.

[JackEllis]

The only load data I have for a bullet that heavy using that powder is in Hornady's 10th Edition for .223 service rifle. Hornady's maximum recommended load is 22.5 grains. You're more than 10% above that.

How are you sizing your brass?

Do you get dings in that location when your cases are ejected (asks the idiot who doesn't know squat about ARs)?

I'm going to speculate that it's a combination of a hot load, brass that keeps getting dented in the same place, and maybe oversizing the cases.

If it was incipient head separation, I'd expect the thinning to be down closer to the web.

[MarikinaMan]

It’s a pretty hot load, but still under Accurate’s maximum for 5.56.

https://imgur.com/a/ejJpZqd

The primer looks flattened with no cratering. I am using standard small rifle CCI primers, the hardened ones for 5.56.

I am full length sizing for semi-auto application.

I worked it up from 23 grains. I feel it’s safe for me. I’m getting 2850 FPS. It’s pretty zippy. I pity the fool that actually gets hit by it.

[croue]

Looks like a bulge all the way around that you may have ironed out during sizing more than once. Might want to check your other brass for ring signs.

Bulge could be from pushing the shoulder back too hard - you are probably fire-forming aggressively with your load. Some cases may buckle slightly. Repeated sizing will exacerbate this.


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[Abenaki]

Thanks for posting that.

I have never seen anything like that before.

I did have a case separation in my AR using LC brass once.
It about a 1/4" below the shoulder.

Thanks again
Abenaki

[jtv3062]

It’s a pretty hot load, but still under Accurate’s maximum for 5.56.

https://imgur.com/a/ejJpZqd

The primer looks flattened with no cratering. I am using standard small rifle CCI primers, the hardened ones for 5.56.

I am full length sizing for semi-auto application.

I worked it up from 23 grains. I feel it’s safe for me. I’m getting 2850 FPS. It’s pretty zippy. I pity the fool that actually gets hit by it.

Lake city brass is 5.56 and has less capacity then .223.
My loads with 2520 with 69 SMK and PMC brass(5.56) shows what I loaded safe in Sierra manual but the brass shows high pressure and Get the occasional case head separation.
The rifle is a heavy barrel Remington 700 with a 5.56 chamber.

Eta I see you have a semi and that adds to it.

[lordmorgul]

Case near failure autopsy

https://imgur.com/a/ejJpZqd

[FLIGHT762]

Lake city brass is 5.56 and has less capacity then .223.

Not true. 223 Rem. brass and 5.56X45 NATO brass are very similar in case capacity. There is 223 brass that has less capacity than some 5.56 brass. It depends on manufacture. 6MMbenchrest has an old test that showed this:

https://www.6mmbr.com/223Rem.html

Not the same as 308 Winchester VS 7.62X51 NATO brass.

I have some GFL (Fioccchi) 223 cases that weigh over 100 grains and have less capacity than LC 5.56 cases.

223 and 5.56 brass capacities are all over the place. Just depends on manufacture.

[MarikinaMan]

223 and 5.56 brass capacities are all over the place. Just depends on manufacture.

I hear some manufacturers will use a stronger brass alloy for 5.56 while others will use more brass to strengthen the case.

[MarikinaMan]

Are you sure with it being slower and that hot that you do not have excessively high gas port pressure throwing that brass harder than necessary? It may not be flying farther but could be slapping back against the deflector a bit hard or catching the ejection port.

You may be right.



Out of an abundance of caution, a trashed 15 cases out of 100. 1 had a split neck, 2 more, 3 in total has case splitting, another 3 had what looked like a crack around the neck. I could feel it inside so I canned it. The rest, I could just feel something inside with the inspection pick. If I feel something, I can it.



Honestly, 5 firings is decent for once fired brass. After I can the rest of this bunch, I will try and buy some Starline brass. Those I would expect to last about 20 firings.

[jtv3062]

Not true. 223 Rem. brass and 5.56X45 NATO brass are very similar in case capacity. There is 223 brass that has less capacity than some 5.56 brass. It depends on manufacture. 6MMbenchrest has an old test that showed this:

https://www.6mmbr.com/223Rem.html

Not the same as 308 Winchester VS 7.62X51 NATO brass.

I have some GFL (Fioccchi) 223 cases that weigh over 100 grains and have less capacity than LC 5.56 cases.

223 and 5.56 brass capacities are all over the place. Just depends on manufacture.

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

https://www.topbrass-inc.com/blogs/news/223-remington-vs-5-56-nato-what-s-the-difference

https://www.topbrass-inc.com/blogs/news/223-remington-vs-5-56-nato-what-s-the-difference

Am I reading this all wrong?
The outside dimension are the same, the difference is that the 5.56 has thicker walls which translates in smaller case capacity.

So you need less powder in a 5.56 case to get the same pressure as the .223.

[lordmorgul]

https://ultimatereloader.com/2018/08...cts-and-myths/

https://www.topbrass-inc.com/blogs/news/223-remington-vs-5-56-nato-what-s-the-difference

https://www.topbrass-inc.com/blogs/news/223-remington-vs-5-56-nato-what-s-the-difference

Am I reading this all wrong?
The outside dimension are the same, the difference is that the 5.56 has thicker walls which translates in smaller case capacity.

So you need less powder in a 5.56 case to get the same pressure as the .223.

[FLIGHT762]

Am I reading this all wrong?
The outside dimension are the same, the difference is that the 5.56 has thicker walls which translates in smaller case capacity.

So you need less powder in a 5.56 case to get the same pressure as the .223.

5.56 does not always have less case capacity than 223. It can in some cases. There is a lot of misinformation about this on the net. People constantly assume it is the same thing between the 308 Win. and the 7.62 NATO. It is not.

I've been reloading for the AR-15 since the early 1970's in the first Colt SP1's. One of my earliest I still have is a 4 digit serial# made in 1968.

I've measured about every kind of 223 / 5.56 brass and in my measuring, the case weight is an indication of case volume. The 100 grain cases have less volume than the 94 grain cases.

I have LC, WRA and TW 5.56 cases from the late 1960 early 1970's.

In the US manufactured 5.56 Military cases Lake City, WCC, FC the cases are fairly consistent, usually around 94-97 grains (weighed W/a spent primer in the case).

Like lordmorgul pointed out, depends on the case batch. You can mix brass when shooting a milder load like 24 grains of H-335 (WC844) with a 55 fmj, but if you want to push it to max @ 26 grains, you will run into issues with thicker brass.

Like I said, a lot of misinformation on the net even from some so called expert sources. Case weight / volume measuring is the way to determine what the actual case volume is. A lot of blog writers talk about but only a few actually do it.

**Edit** @ lordmorgul, those Speer nickel cases are some of the most consistent weight wise. I have a few thousand of them once fired from L/E AR-15's.

[the86d]

I have seen certain rifles dent brass at this location when ejected, and I reloaded it anyways (free range brass), shot it, and the brass chamber-formed correctly, but never really had an issue like this.