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Bright ring question...pressure or something else? (yes, with picture)

Infinity

Infinity

Always Professional
Full Member
Minuteman
Apr 17, 2012
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Atlanta, GA, USA
Hi All,
I'm in the process of working up a FGMM clone load with LC 93 brass trimmed to 2.008", 175 SMKs seated to ~2.810", F210 primers, and Varget.

Today, I worked up to 42.9 grains (2527 fps) when I noticed a potential need to slow down. Figured it was worth asking those with more experience than I. My FGMM and my RL-15/FC brass hand load chrono @ 2570 fps out of my LAR-8 w/ 20" barrel. If it is safe, I still want to increase the charge of this LC brass/Varget combo until I match velocity of FGMM and my clone load.

I'm not seeing any flattened/cratered/leaking primers. The only thing I see that may be a little warning is...in the below picture, note the slightly bright ring just above the case head. It seems like this is a little too low to be impending case head separation but please let me know if I'm wrong. Is it possible that this light ring is from something other than too much pressure? Can I keep going if the case passes the "paper clip" test as long as I'm very cautious? Can this case be reloaded again or should I just toss it? Please feel free to contribute anything you may find helpful...(and please spare the read your reloading manual...I have and have worked up past published max loads a few times successfully). Thank you much,
Adam

 
That ring is usually from the sizing die, cinching down on that expanded portion of the case. It's an abrasion that you might not see if the brass is all pimpy looking when you size it.

Chris
 
Looks like it could be an impending case head separation . . . or as Chris says, just marks from the sizing die. The pic is not really clear enough for me to want to say for sure.

Are you using a bump gage, or some other method of verifying just how much shoulder set-back you're creating when sizing? If it's a head separation issue, this is where it comes from, and how it's cured. So long as you're not bumping the shoulders back too much (probably no more that about .006" or so), then it's probably not the head separation. Check with the paper clips, or better yet, run a bore scope inside and take a look. The "trench" that forms on the inside of the case walls is clearly visible, if that is indeed the problem. Or, you could sacrifice a case or two (worst looking ones) and simply cut the case lengthwise on a band saw so you can see the interior. Little more digging here, and you can probably figure this one out.
 
Shine a flashlight inside and look for case thinning near where the ring would be. That's high enough that it could be incipient case head separation, which is caused by excess headspace, not excess pressure. FYI, I've had case head thinning with a .004" bump, before, so never rule out the possibility of case head separation.
 
ksthomas said:
Check with the paper clips, or better yet, run a bore scope inside and take a look. The "trench" that forms on the inside of the case walls is clearly visible, if that is indeed the problem. Or, you could sacrifice a case or two (worst looking ones) and simply cut the case lengthwise on a band saw so you can see the interior. Little more digging here, and you can probably figure this one out.
Click to expand...

There's your answer
 
If the load is moderate, you might have excessive headspace situation. Double check you a resizing just enough and not too much. As for the cases with the bright rings after firing, check them with the bent paperclip; if any of them fail, toss them all.
 
Looks like a normal burnished expansion ring to me.
 
I think you're ok. I get the same thing from my M1A's and it is very common in semi 308's. Has to do with what happens after the explosion nd the bolt cycles while the brass is still very hot and malleable. The case is still 'stuck' to the inside of the chamber wall when the bolt cycles...everything behind the ring is still enclosed by the bolt head and not touching the chamber. Once the ring appears I can only get about three more loads before the brass is scrapped. It is the begining of an incepient seperation but the brass is still usable
 
Thank you everyone for the replies. For some reason, my email notifications weren't working on this thread (I was just getting ready to bump it). Anyway...

Chris, I was hoping as much. Thomas, I am not using a bump gauge. The rudimentary (paper clip) option will probably shine the most light. Temp, thank you also for weighing in. I'm not ruling out the possibility of impending case head separation, I just don't have any paperclips at the moment (I was pretty surprised by that). RTK, that definitely seems to be my next course of action. Buffy, will do. Fuzzball, thank you. Insight, that experience definitely puts me at ease a bit.

As soon as I am able to find a paperclip, I will report back with results. If I had a bandsaw, I would go that route. Thanks again all, Adam
 
"...the begining of an incepient seperation "? The problem is a head seperation; "incepient" means beginning.

Forget paper clips, get a steel #8 or #10 crochet hook from Walmart's lady's crafts dept and use that instead.
 
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Thanks all for the replies. I work tomorrow but will let you all know if/when it passes the paperclip/crochet hook :)D) test. Cheers,
Adam
 
In case anyone was interested, was a sizing mark. The good 'ol paperclip test confirmed and I've gone quite a bit hotter since. Thanks all for the contributions...
 
Paperclip test is cool but I would still cut one open and check it out. More than pressure, improper sizing is more of a culprit for case head failure.
 
roggom, good advice... I am sure I was oversizing before and am just waiting for my bump gauge to come so I can readjust my die. Before loading this brass for the third firing, I will open one up and get back with pics/info. I have a bunch of this LC brass prepped. Assuming I haven't run into any issues over 15/20 rounds (I'm not in front of my notes and I am loading almost a full grain below where I was running into pressure signs), is it fair to assume I'm good for this go around?

I haven't shot that rifle/brass much as I've been prepping for a new custom. Thanks,
Adam
 
I have had case head failure before. I spent a lot of time on brass prep: cleaning, chamfering, annealing etc. and was able to get many reloads from the same brass. Before I got my RCBS precision mic, I was just resizing to where I thought was good to go. Fit in the chamber so it must be good; well I was wrong. It only took one case head to fail to make me look at this seriously. It kinda sucked having to throw around 50 Lapua cases in the recycle bin, but it was a lesson I learned the hard way. Now I have a RCBS Precision mic and Hornady headspace guage kit.


Since I have two 308 rifles, I now have one set of dies for each rifle. I also check shoulder bump with each type of brass I use. It really doesnt take too much time to set shoulder bump.

Here are some pics of my failed case, a cross section, and another case of the same batch that i had to chuck in the bin.
 

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Thank you again for expounding and for the pics. After how may firings did you get the case head separation?
 
That was about 12-14 as I anneal at 8. Bummer because the case mouths and primer pockets were still serviceable. This was with a mid pressure node 178 Amax over 44.4 Varget. WLR primers seated 2.830
 
Really good info, thank you again. It's nice to be able to benefit from your experience where mine is lacking. Even though I'm sure they're okay, I will cut a few open after the next firing to be safe. After that, I will send them out to get necks annealed.
 
I have had several head separations and incipient head separations over the years and I have never seen one that has a perfectly concentric ring. The reason is that the taper of the brass at the body to head juncture varies in wall thickness at any fixed distance from the head. A perfectly concentric ring is either a chamber mark, sizing die mark or the mark that the top of the baffles in a plastic cartridge box makes when cartridges are placed upside down in the boxes and are subject to a lot of vibration from transportation. I will admit that it is possible that you can find an occasional case that has a separation ring that appears to be concentric but if many in a batch have perfectly concentric bright rings at the same distance from the head then it not a separation issue.
 
If your bolt gun closes the bolt on a handloaded cartridge without exhibiting a small but definite degree of bolt drag, there's a good possibility the shoulder is being pushed back more than is optimal.
 
I agonized over this type situation. Some here agonized just hearing about it.
My solution was to saw some lengthwise and see. Mine too were just fine.
 
old thread but certainly interesting. I currently have this issue with 325wsm(Winchester brass). Been wondering about imminent case head separation. I’ll cut open a few random pieces to get an indication. It’s the best chance to be sure. Good thread/ good advice- thanks all.
 
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