Sheared pressure ring?

[Rflshootr]

I was working up a load with a new powder (Sta-Ball) for a 7-08 with some old lot 120 Sierras, made in California, and after 15 shots I cleaned to switch powders, and on the first patch, this came out. Shot these bullets with other powders and no problems. I called and emailed Sierra and they told me that no one there has ever seen this happen. Anyone ever seen anything like this before?

 

[rsmithsr]

I was working up a load with a new powder (Sta-Ball) for a 7-08 with some old lot 120 Sierras, made in California, and after 15 shots I cleaned to switch powders, and on the first patch, this came out. Shot these bullets with other powders and no problems. I called and emailed Sierra and they told me that no one there has ever seen this happen. Anyone ever seen anything like this before?

View attachment 25549

ya need to chamfer the case necks and they are probably too small, and too hard

 

[Rflshootr]

Brass was annealed, trimmed and chamfered with a VLD style tool one firing before.
The bullets seated fine with no unusual resistance in the brass, no shaving of the jacket.
The copper ring came out of the barrel during cleaning, after 15 rounds were fired from a new barrel with 100 rounds through it. The previous 100 rounds fired had no problems.

 

[Al Nyhus]

One thought....take a good look inside the case necks at the neck/shoulder junction area.

Did the last round hit wonky on the target or did it go where it should have? -Al

 

[Rflshootr]

Al,
If you're asking about a donut, I don't see anything. The brass is starline which has a thinner neck then some other stuff. I measured the fired case and a loaded round and there is .006 difference which is a pretty big amount.
The last round stayed centered but was about 2" high.
The bullets are pretty old, but not corroded. They have a slight bit of tarnish but nothing out of the ordinary.
I'm wondering if it was a bad jacket. Maybe a stress crack or internal corrosion that isn't visible. Or maybe when the jacket was drawn it was too thin at the base for whatever reason. I don't know....never had it happen before that I'm aware of.

 

[antelopedundee]

I was working up a load with a new powder (Sta-Ball) for a 7-08 with some old lot 120 Sierras, made in California, and after 15 shots I cleaned to switch powders, and on the first patch, this came out. Shot these bullets with other powders and no problems. I called and emailed Sierra and they told me that no one there has ever seen this happen. Anyone ever seen anything like this before?

View attachment 25549

That looks ragged. One ring or an accumulation?

 

[Rflshootr]

It appears to be one piece. But with pressure, I guess it could be welded together. Don't know. It came out just like you see it on the 1st patch with Butch's Bore Shine. Hey what a great advertisement that would be for removing copper.

 

[OliveOil]

Have you look to the chamber neck of this "new" barrel with a bore scope or even a magnifier lens?

I wonder about :

a : too long chamber neck

b : a circular groove at the very front of the chamber (very front of the neck) in the case some chips got caught in between reamer and chamber/neck wall.


With regard to oxydation on old bullets, have them seat point up in white vinegar or vinegar for 10 minutes and you will end with green tip bullets that should make you happy.

 

[Rflshootr]

Have you look to the chamber neck of this "new" barrel with a bore scope or even a magnifier lens?

I wonder about :

a : too long chamber neck

b : a circular groove at the very front of the chamber (very front of the neck) in the case some chips got caught in between reamer and chamber/neck wall.


With regard to oxydation on old bullets, have them seat point up in white vinegar or vinegar for 10 minutes and you will end with green tip bullets that should make you happy.

a: Huh? The bullet doesn't touch the chamber. How would that cause a problem?

b: Huh? If the chamber had a groove, which it doesn't, the brass would flow into that groove making the inside of the neck bigger in that area. How would that shave a bullet?

Oxidation....why would anyone want to do that? HUH?

 

[R.G. Robinett]

a: Huh? The bullet doesn't touch the chamber. How would that cause a problem?

b: Huh? If the chamber had a groove, which it doesn't, the brass would flow into that groove making the inside of the neck bigger in that area. How would that shave a bullet?

Oxidation....why would anyone want to do that? HUH?

A 'shaved' jacket would be my last guess . . . even then, at best,on my part, a SWAG of gigantic proportion . . . I'm leaning toward something similar to 'OliveOil's question: a piece of cartridge case - a hanger-on from trimming/chamfering, which simply occupied the gap between the case mouths and chamber mouth, with the bullets passing through . . . , then, the patch latching onto the ring(s) . . . RG

 

[antelopedundee]

a: Huh? The bullet doesn't touch the chamber. How would that cause a problem?

b: Huh? If the chamber had a groove, which it doesn't, the brass would flow into that groove making the inside of the neck bigger in that area. How would that shave a bullet?

Oxidation....why would anyone want to do that? HUH?

Old bullets tend to lose that "new" look just like copper cents do. This is due to simple oxidation and is often referred to as tarnish. That new look can be restored to ultra new by exposure to vinegar. It removes a surface coating of oxides exposing new copper. Same as polishing tarnished silver. I've never done it, but I suppose one could do the same thing with their cases. I doubt that it will do anything for the inside tho. Be sure to rinse them well.

 

[Rflshootr]

A 'shaved' jacket would be my last guess . . . even then, at best,on my part, a SWAG gigantic proportion . . . I'm leaning toward something similar to 'OliveOil's question: a piece of cartridge case - a hanger-on from trimming/chamfering, which simply occupied the gap between the case mouths and chamber mouth, with the bullets passing through . . . , then, the patch latching onto the ring(s) . . . RG

Well I normally hit the mouth of the case on a piece of scotch brite after trim and chamfer to remove any burr that the chamfer tool may have left and the ring is clearly copper and not brass. So dang if I know.

 

[R.G. Robinett]

Well I normally hit the mouth of the case on a piece of scotch brite after trim and chamfer to remove any burr that the chamfer tool may have left and the ring is clearly copper and not brass. So dang if I know.

Roger this . . .

The [so called] pressure-ring, is normally about 0.0003" to 0.0004" over the nominal bullet diameter, thus, even if the P-R could/did shear off, at best, would be only about 0.0002" 'THICK' - <1/10th the thickness of a human hair.
Residing in the fire-blast zone, its difficult to imagine that the ultra thin gilding metal wouldn't have been vaporized, and possibly deposit along the bore . . . ???? Surely, this is a weird one.RG

 

[Rflshootr]

Roger that! And it figures it would have to happen to me.

 

[OliveOil]

@ Mr. HUH :

Are you using a motorised case trimmer ?

Have you noticed some heavily copper fouled areas here and there down your almost new barrel when using your bore scope ?


ps : if chamber was grooved in the throat/lead area, my guess is that a bullet under full acceleration will expand in the groove (a la Minié effect) and get somewhat shaved, plating/filling the groove with some gilding metal shot after shot. THAT should be felt as a hard point when using a tight dry patch after cleaning.

I also DO suppose that the chamber is cut on the very barrel axis and NOT out of barrel axis, in which case the bullet wobles badly once the ogive enters the rifling.

 

[Al Nyhus]

With a VLD tool, the necks can get pretty thin at the mouth. Depending on how big the chamber neck is, it's possible that the very end of the neck could do an 'Exit, stage right' thing when the neck expanded and got pushed into the bore by the expanding gases during firing. That your case length on that round is .006 shorter might fit with that as well. -Al

 

[Rflshootr]

@ Mr. HUH :

Are you using a motorised case trimmer ?

Have you noticed some heavily copper fouled areas here and there down your almost new barrel when using your bore scope ?


ps : if chamber was grooved in the throat/lead area, my guess is that a bullet under full acceleration will expand in the groove (a la Minié effect) and get somewhat shaved, plating/filling the groove with some gilding metal shot after shot. THAT should be felt as a hard point when using a tight dry patch after cleaning.

I also DO suppose that the chamber is cut on the very barrel axis and NOT out of barrel axis, in which case the bullet wobles badly once the ogive enters the rifling.

Jeeeez Dude.....I cut the chamber and yes it is on axis within .0003 according to my indicator and no it doesn't have any torn metal, grooves or other wise in the chamber body, neck area or throat as verified by my bore scope. The head space is perfect and exactly on minimum. The neck length in the chamber is controlled by the reamer. This isn't my first rodeo. There was some small amount of fouling during break in of the barrel, but that quit after the 1st 20 or so rounds. I had 114 rounds down the barrel without a hitch, until number 115. The barrel was cleaned every 20 rounds or less after break in and there was very little copper in the bore. What does a motorized case trimmer have to do with it? Why don't you admit you've never seen this before like me and trying to find a crazy problem that has nothing to do with what I suspect was a bad bullet jacket that was made 30-40 years ago? If it was the throat causing it, my guess is that the copper ring wouldn't be full bullet diameter or an unbroken ring. I already said that I make sure there are no burrs on the mouth of the case by spinning the case mouth on scotch brite. Sooooo tell me, how many times have you seen or experienced this yourself? And please do us a favor and learn to use spell check. Thank you Sir. Sorry Dude...I know you're just trying to help.

 

[Rflshootr]

With a VLD tool, the necks can get pretty thin at the mouth. Depending on how big the chamber neck is, it's possible that the very end of the neck could do an 'Exit, stage right' thing when the neck expanded and got pushed into the bore by the expanding gases during firing. That your case length on that round is .006 shorter might fit with that as well. -Al

Al, then wouldn't I see a case mouth that was screwed up or shorter then the rest that were all trimmed to the same length? I looked at those last 15 cases and nothing seems out of place.

 

[Al Nyhus]

Al, then wouldn't I see a case mouth that was screwed up or shorter then the rest that were all trimmed to the same length? I looked at those last 15 cases and nothing seems out of place.

I misunderstood your statement about .006 to mean the case length was .006 shorter on that round. Reading it again, you were clearly referencing neck diameter, not case length. My bad.... -Al

 

[Rflshootr]

One thing I might add is that the reamer has zero free bore with a 1.5° lead. I don't think that is the cause because I chambered 2 other barrels with that reamer and haven't had an issue from either one of them. The only thing that I can come up with is a bad jacket for whatever reason. So far that is the only thing that seems plausible to me.