Impending case head separation?

[Fat_46]

I'm working up loads for my .243 Prairie Dog rifle. All loads were either .5 grains or 1 full grain under maximum - but I am getting the shiny ring of doom:

I've never had it happen before, so I'm guessing its too hot a load for this rifle.

Does that ring look like a head separation starting? Or am I being too careful? The brass shows no other signs of pressure, and are the same length as before firing.

Load info: 42.0 or 42.5 grains of H4895, new Winchester brass, CCI Bench Rest primers, and a 58 grain Hornady VMax

Rifle info: Savage 110 LA, Shilen 26" bull barrel


Thanks for the advice...

 

[ocabj]

Honestly, it's hard to tell from that picture. Use the macro feature on your camera if it has one, use a tripod, and turn of the flash.

 

[Steve in PA]

Its a mark from the die.

 

[Walkalong]

Yep. can't tell.

Get a feeler of some sort. A paper clip will work. Straighten it out and bend about 3/16 to 1/4 " 90degrees and slighlty sharpen the short part. Use it to feel inside the case. If it is bad you can FEEL the place where it is going to seperate. It feels like a small "ditch" going around the inside of the case where the brass is thinned and ready to let loose. A shiney spot caused by the case expanding to fill the chamber and then sizing is not necessarily a danger sign.

Like Steve in PA said. I can only see a normal sizing mark.

 

[ReloaderFred]

The photo isn't clear enough to tell (at least on my old monitor). The easiest way to tell is to bend a large paper clip straight and then on the last 1/8", bend a 90 degree angle and sharpen the point of the angle piece. Run this "tool" down into the case and right in the area of the ring, see if the point catches on an uneven portion of the case, just above the web. If there is a weakening of the brass, it will be in this area and you'll feel the point drag into the groove.

My guess is the shoulder of the case is being set back too far for the chamber during sizing, causing the case to stretch more than it should upon firing. You only want to set the shoulder back about .002" to .003". The over all length of the case may not change, but if the shoulder has to move during firing, then it will pull brass up into that area, stretching the case where it's the weakest, at the juncture of the web and wall of the case.

If you have a case that's been fired and there is resistance to the bolt closing on it before sizing, then use that case to set up your sizing die for that chamber. Just unscrew the sizing die about one full turn and then size the case. Try it in the chamber and if you still have bolt resistance, screw the die down about 1/4 turn and size the case again. Keep doing this until the bolt will just close, with little to no resistance. Then tighten the lock ring and the die will be set up properly.

One of the best tools for doing this is the RCBS Precision Mic tool. There are others, but I use those and they work great.

Hope this helps.

Fred

 

[ReloaderFred]

We were all typing at the same time!!

 

[Fat_46]

Thanks for all of the advice. I did the paperclip thing, and couldn't feel anything. Then I decided, what the heck and used a Dremel with a fine cut-off wheel on a few different cases. The mark must be from the sizing die, and the case wall in uniform near the head on all 4 cases I checked.

Thanks again!

 

[Sunray]

"...from the sizing die..." Yep. You can forget about it. It's normal.
What's the rifling twist in your barrel? You may find those 58 grain bullets are too light if the twist is too fast. The .243 shoots light bullets best with a slow twist. 1 in 12 will do it nicely. A 1 in 10 may not. A 1 in 9 or 9.5 won't.

 

[Fat_46]

Its 1:10...but seemed to shoot the 58s pretty well!

I'm trying to work up a load for some late July South Dakota prairie dogs, and like the ballistics of the 58 gr. VMax.

 

[Walkalong]

Case "feelers" and a mirror, compliments of the Docs at work.

 

[Stinger]

From what I can tell because of the resolution, it is not a shiny ring, but die marks on the brass.

Stinger

 

[snuffy]

Fat_46, I had the same bright ring show up on some .308 shells last week. I traced it down to having the FL sizer screwed down too far. How I know this is through the use of a wilson case guage I just got last week. Here's a couple of pics I just took;

And yes there is a sharp ring on the INSIDE of these cases. They would most likely seperate on the next firing, IF they were resized with the die set the same.

As to why they want to seperate this far up on the body of the case, I don't have a clue! Usually, case head seperation takes place just ahead of the extractor grove about .375 to .500, were the web meets the case body.

I just looked on the midway site, they have a headspace guage for the .243 win, just like the guage pictured with those cases of mine.

http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=653047

That gauge showed that I was sizing .010 too much! Or .010 below the low datum line of the guage. In doing some research on the use of this guage to set a sizer die, I found they recommend that the case be sized to arrive half way between the minimum and max on the guage. Of course, the sized case should then be tried in the rifle, to see if it will close on the empty case.

I'd be willing to bet that you have the early signs of case head seperation showing up in those shiny rigs on your cases. Not all of the shells I had with the rings outside had a corresponding ring on the inside, but about 50% did!

I'd also bet you have your sizing die set down too far, setting the shoulder back too much, creating excessive headspace. The only way to tell for sure is with a guage.

 

[ranger335v]

There is a potential problem with setting a sizing die with a Wilson type cartridge gage; you will only be sizing back to "normal" SAMMI specifications instead of what YOUR RIFLE actually needs!

For maximum case life due to best chamber fit, I second the suggestion of the RCBS "Precision Mik" to find the case shoulder location from YOUR RIFLE. Just measure a fired case and set the size die to move the shoulder back a couple thousants from that point. You will then have a snug chamber fit that reduces case stretching.

Ignore the Mik's bullet seating plug thingy tho, it sucks. But the shoulder and bullet seating depth gage nuts are great for knowing what you are actually doing when adjusting sizing and seating dies.

 

[snuffy]

For maximum case life due to best chamber fit, I second the suggestion of the RCBS "Precision Mik" to find the case shoulder location from YOUR RIFLE. Just measure a fired case and set the size die to move the shoulder back a couple thousants from that point. You will then have a snug chamber fit that reduces case stretching.

Thanks for the heads up Ranger. But can't I do the same thing with the wilson headspace guage and my caliper, by using the depth measuring feature? Sizing to the mid datum line, then fireing that shell in my chamber, then measuring again in the wilson guage?

Fat_46, here's the RCBS precision mic for .243.

http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=375435

I just put one in my shopping cart for 7-08. If I like it for that, I might get one for .308

 

[Sunray]

"...seemed to shoot the 58s pretty well!..." Rule Number One then. If it works, don't fix it.