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Discussion Starter #1
Never seen this before but it makes me think that the ding the 556 puts in the brass may be an issue after all. This was a third time reload of a LC NATO case with a Hornady 75gr BTHP loaded with 24gr BLC -2 powder and SRP. It fired fine and accurately but jammed the rifle upon extraction which was quickly and easily cleared by yours truely :)
 

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Zeus, I have had that happen to me a couple of times, but only when I shot a reloaded shell out of my Thompson Center .223 that I had first shot out of my 556. I mean, it has not happened in my SIG, but it started happening all the time after 2-3 reloads in my Thompson Center using shells resized from my SIGs.

Apparently the 5.56mm NATO chamber is not quite the same dimension as the .223 and it would do that after 2-3 loads.

Normally I use 25.0 grains of BLC-2 with the 75 grain pills and the case necks would split after 5-6 reloads and I would toss the case in the trash.

I was using my RCBS X-Die for the SIG 556s and still am with the die set to full length resize with the die set 1/8 turn after contact with the ram's shell holder.

I purchased a new Dillion .223 carbide die and set it up specifically for shooting .223s in the Thompson/Center without full length resizing completely, ie I am only using SIG 556 reloads in the SIG now and .223 Thompson/Center reloads in the T/C.

I set the Dillion die to contact the ram shell holder and then backed off the die 1/8th turn.

I also have a RCBS Precision Micrometer to check the shoulder. The SIGS have always been resized back down to 0.000 or 0.001 (SAAMI spec is 0.000) on the Micrometer. But when looking at the T/C shells, they were +0.008. Crushing them back down to 0.000 was leading to incipient case head separation.

Fired shells from my SIGs are normally 0.004, while from the T/C they were 0.008 b efore I resized them back to 0.000.

After keeping the SIG 5.56mms in the RCBS segregated from the T/C .223 shells, I no longer have the problem.

You may want to get a RCBS Precision Micrometer and see what the shoulder setback is on a fired shell from your SIG and then remeasure after you have reloaded using your die.

You can also bend a paper clip and run the long end down inside the shell if you visually see a bright ring around the case after resizing to check for case head separation.
 

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Here is an article on using the RCBS Mic to measure your headspace and set your resizing die accordingly for your rifle.

http://www.realguns.com/archives/035.htm

Like I said, when I did this on fired cases both my SIG 556 5.56 NATO rifles they were at +0.004, but the T/C was at 0.008.

Both my SIGs need little resizing as long as I shot the reloaded rounds again in the SIGs.

But my T/C can handle a significantly less resized round, now I am basically just doing a neck-size on it and leaving it longer, but NOT shooting the T/C reloads in the SIGs or vice versa....
 

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As we all know, the 556 has a massive extractor and a "vigorous" ejection. This puts a lot of stress on a hot case. The case stretches and creates a weak point over time (Multiple reloadings of the same case). This point will vary from case to case due to variances in case wall thickness. You might wanna start checking your cases after you clean them, but BEFORE you re-size them for a thin pale line around the case. This is the key indicator of incipient case head failure.

It was an LC case. Was this case part of a new, unfired lot? Or did you purchase it as part of a once-fired lot?

Leb
 

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When I get a chance, I'll take some pics of four of my shells with the bright ring crease around them indicative of incipient head case separation and the one I have that totally separated like Zeus's. It is pretty easy to see and differentiate from simple brass resizing rings caused by the die.

I keep them on the ledge next to my reloading press to remind me about this when I am working.....

The good news is that as long as the brass separates that far up the case the gas is still going out the barrel. The bad kind of separation is within 1-2mm of the rear of the case.
 

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Discussion Starter #6
Leb, this case was a once fired piece, on it's 3rd reload. I will keep a better eye out for this in the future but I load on a single stage press with very good attention to detail and never saw any indication of a problem.
 

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Thought so. When I buy/police up once-fired LC, I go into it knowing that I'm gonna scrap about 10-15% after 3-4 loadings. Most of the brass will come from M16's/M4's, but some of it will have come from an M249, which is a lot harder on brass when it extracts and ejects. And if you're re-loading .308, NEVER take brass that came out of a M240/M60 - The extraction is very stout and stretches the case something fierce.

Sorry that happened to you, bro. Is the chamber to your 556 okay?

Leb
 

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Here are a couple of examples of my split cases.

You can see the incipient case head separation and feel it with a paper clip inside the case too.

This happened to me after just 2-3 reloads in cases that had been fired in either one of my 556s and then reloaded and fired in my T/C .223.

Now I have two separate dies, one for the 556s and one for the T/C to avoid crushing the shoulder down too much.





Normally I get 5-6 reloads out of each case before the case neck splits on me and I toss the case.
 

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The cause of this problem was that I was full length resizing the cases for the 556, pushing a case expanded out to 0.004-0.006" back down to 0.000.

Then when I fired them again in the SIGs, they work fine, no problems for 5-6 reloads.

However when I fired them in the .223 Thompson Center rifle, they expanded out to 0.008-0.010, which is TOO MUCH. Now I just resize the cases from the T/C .223 back down to 0.005 and they work fine in this rifle, but not in the SIGs.....
 

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Excellent photos!
 

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Thanks, it was difficult to take those photos indoors, could have gotten a better shot close up outdoors in some bright sun but at least you can actually see the lines on the cases.

The good news from all this is that the headspace on both of my SIG 556s is right on with very tight close tolerances, which demand that you full length resize every single case! 8)

With the T/C I can get away with just neck sizing......
 

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This is happening to me also with new Federal ammo I bought from Academy. I have not had the chance to try any other ammo yet though. I took the broken brass to the gun show to let one of the guys look at it who reloads. He told me it was a headspace problem with the rifle and I should send it back to Sig to let them make it right. What are your thoughts?
 

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First, have you tried any other ammo?

Is this the only type of ammo you have used, or you've used other types of ammo and it only does it with this kind of ammo?

How often has this happened to you.

It could be a bad batch of ammo and it could be a headspace problem. You could have a gunsmith check the headspace for you and if it is off you will need to send it back to SIG to have them correct it under warranty.
 

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I have not tried another type of ammo yet. That may be my next step before packing it up again and sending back to factory. It has happened to me about 15 or 20 times out of 400 rounds. I also cannot get the rifle to zero either. As I said, I might try a higher quality ammo and see what happens.
 

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It could be a headspace problem, but more than likely you have been bumping the shoulder back too much. Do you have a Chamber/case gauge? They work great to see if you are oversizing your brass.
 
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