Odd [very minor] crease found just below 30.06 case mouth - any ideas?

[zambezi]

Routine 30.06 case prep on three-times fired cases threw up an odd feature. But not on all cases...

Approx 95 Sako brass and just 5 Federal cases in this batch. Perhaps 90 of the Sako show some degree of crease, and five did not. None of the Federal have any creases.

Visually, the creases look like this: and the ones with no crease look like this:

The re-sizing die uses an expander ball, so I suspect the internal ridge has been flattened and thus poses no issue to bullet grip variation.

My conundrum is that I do not have any process in the shooting [bolt imparts just a 60° lift] or subsequent case prep that might impose a 360° rotary-motion induced scoring all the way around the case mouth.

So where has this come from? [unfortunately I do not have any virgin brasss with which to compare] Does Sako factory ammo include a crimp? If so, I never spotted this before.

Any ideas?

 

[sikadog]

The only thing I have ever Seen like that before was from a chamber that was cut incorrectly. What length are your cases trimmed too.

 

[zambezi]

What length are your cases trimmed too

Cases all trimmed to 2.490" [within SAAMI spec]

I ran my borescope down the barrel and other than the camera suggesting that there is a bit more carbon in the throat area than might be ideal, there is nothing untoward. This rifle was second hand when I bought it 7+ years ago. So nothing new there.

For all I know, all my Sako brass has looked like this from the get-go, and it is only on this occasion that I spotted the feature?

 

[NP435]

Cases all trimmed to 2.490" [within SAAMI spec]

I ran my borescope down the barrel and other than the camera suggesting that there is a bit more carbon in the throat area than might be ideal, there is nothing untoward. This rifle was second hand when I bought it 7+ years ago. So nothing new there.

For all I know, all my Sako brass has looked like this from the get-go, and it is only on this occasion that I spotted the feature?

View attachment 279682

Looks like a stab crimp done at the factory.

 

[zambezi]

Looks like a stab crimp done at the factory.

I am tending toward that idea. See image below. Just odd that I cannot see it on 5 Sako cases.

My only other revelation was this: when I reviewed the images I posted in #1, I realised they looked sooty, with resizing die score marks evident in the soot. That made no sense as the ultrasound bath is my step #2 after depriming and before resizing. So...

...I stripped the resizing die and was horrified to see how gungy that was. Certainly there was a ring of black sludge in the area of the die that corresponds to the case neck. But it was amorphous gloop, not sharp swarf.

Die is now fully cleaned, and cases were passed through ultrasound bath for second time.

The twice-cleaned Sako cases shown in front of the once-cleaned Federal below.

Now fully clean, the scoring definitely looks to be a sequence of six equally spaced indentations, not a continuous gouge all the way round the circumference. I.e. this looks to be introduced by a collet-type multi-petal tool, not a rotary-action induced wear mark. [my RCBS dies are not of the collet type]

 

[NP435]

There is something to be said for a clean die set, if you have the product Corrosion X coating the sizer die and letting it dry results in a slippery die that won't need as much case lube.

 

[andyk]

Pretty sure that’s the factory crimp. I’ve reloaded .30-06 Sako brass and have seen the same.

I’ll try and dig some out when I’ve finished my house move.

I do recall that not all seem to show it as obviously.

 

[Bowland blades]

something in or on your die or sizing button ?

 

[zambezi]

something in or on your die or sizing button ?

None visible .[RCBS die is all-in-one. I.e. no separate button/collar]

Besides, I cannot see how a random imperfection in the die [or rifle chamber] could impose 6 identically sized indentations at equal spacing around a circle. That is the signature of a collet, surely?

The more I look at this, the more convinced I am that DTS is correct: it is a factory stake crimp. [all my Sako brass was originally purchased as factory 497A ammunition, not unfired brass. And I have found a Sako resource describing the use of crimps on their current Powerblade offering in some calibers]

But I am baffled as to why I did not see it on one of the previous reload cycles.

 

[One on top of two]

That’s from a crimp .

Load em up

 

[260madman]

Yep. Factory crimp.

 

[Foxyboy43]

Crimp marking for sure. Sako are a great brand and a good crimp is the way to go…..

 

[andyk]

Isn’t showing too well in the photo but here’s one of mine. Factory brass reloaded.

It looks more obvious “in person” than in the photo.

 

[zambezi]

here’s one of mine. Factory brass reloaded

That is a definite match for what I can see on my Sako brass too. Many thanks for the confirmation.

 

[andyk]

No worries. They almost seem to “iron in”, starting off as a more obvious crimp and then getting flattened with sizing and further firings.

 

[25 Sharps]

It’s a crimp!

 

[Muir]

Yes. A crimp. ~Muir