Case head marks - help

caorach

Well-Known Member
I have been noticing some radial marks, scratches, on the heads of my cases. I can't say for sure if these are happening in the reloading dies, or the priming tool or in the actual rifle when shooting and so need to do lots more research but I thought to ask here just in case anyone has seen this before. The rifle is a Blaser R93 so it is straight pull but even so I have a feeling that it might turn the case slightly on extraction, though not my enough to leave these marks I suspect. The background is that this is a 308 and I've been working up a load for about 2 - 3 years now, I'm in no rush and new to this so it is all an adventure. I suspect that the marks have appeared fairly recently but am confident I am seeing them on cases with very moderate loads as well as on cases with my "deer" load. All loads are within printed book max for what that is worth. Here are a few photos:

primers3.jpg


radialscratching.jpg
 
How about buying a box of factory "unmarked" ammo & firing them off. If no marks then you can at least eliminate the rifle as the cause.
 
I haven't noticed this with factory ammo, but then I don't shoot much factory ammo now that I reload.

I also haven't noticed any foreign bodies on the bolt face, or on my dies for that matter either.

It is a bit odd as the marks look, to me, like they have quite clearly been made by some hard foreign object which has cut into the case as either the case or the object are rotated. There is no sign of smearing of the lettering, for example, which would be a clear pressure sign and I'm not seeing any other pressure signs. I do have some new Lapua cases here which I could do testing with but I thought to ask just in case someone out there with more experience than I would step up with "I know what that is, you need to back off..."

One reason why I'm interested in opinions is that I managed to shoot my current "deer" load over the chrony this morning and the results were interesting, my previous load turned out to be giving me marginal deer legal velocity so I've worked up a little.
 
Caorach, that mark you have on your cases is a "witness mark", engineer speak for two or more metallic faces that have contact, either together or with something extra being introduced between the faces, you will have an opposite surface or feature that will be making these marks, as they appear to be rotational, that would suggest the bolt face is making them, even a very small projection can be the cause, have a real good look under some magnification...... if it's a box mag, also check the ends of the lips on the box.
 
I hope you are right finnbear, though your answer is what i was wanting to hear. My concern was that it was, in some way, in indication of pressure but as you say it looks like a witness mark of some description. That being the case my best bet is that it came from one of the shell holders rather than the bolt as factory ammo is all ok plus my Blaser is a straight pull and so may not rotate the case much on extraction.
 
Caorach,
You say you have some new Lapua brass? why don't you put them through the press, & check them, then you'll notice any marks. If none then look for the foriegn body on the bolt face. But to be sure try some factory fodder as-well.

Atb,

Moe..
 
I also have a Blaser.

The bolt head is captive and cannot rotate.

Therefore I do not think that the marks are caused by rotation of the bolt head on the case.

Likely is a burr on the mag lips or foreign body on the bolt head itself.

It is also possible that there is something in the case holder of your press which has created the witness mark when you FL size the case.


I think you will find something on any of the three possibilities mentioned that has caused this.


I dont know if you bought these cases new or aquired them from a third person ? - there is also a possibility that the marks were there when they came into your hands.....


Try new brass after cleaning, bolt head, checking mag and cleaning case holder.
 
I also have a Blaser.

The bolt head is captive and cannot rotate.

I dont know if you bought these cases new or aquired them from a third person ? - there is also a possibility that the marks were there when they came into your hands.....

Thanks for this Redmist, I was sure I had read that even the Blaser rotates the head slightly to get extraction, but I could well be wrong on this as like you say I can't see how it can possibly do it.

The cases were new so I'm causing the scratches somehow. What it will need is me to get a new case and introduce it into the system and monitor its condition at each stage until it gets marked. I have a sort of feeling, which I can't support, that it is happening with the shell holder in my Lee hand priming tool. As you can imagine my main concern is that it isn't some obscure indicator of pressure. The cases have been reloaded, using this load, several times now and primer pockets are still tight plus as can be seen from the images there are no clear pressure signs. However on Saturday I shot one over the chrony and the velocity was, to put it mildly, remarkable. That caused me to step back and examine things again and these scratches were the only strange things I could find that were unusual, however I'm pretty sure they came into being with much milder loads.
 
The bolt head and collets on the Blaser are held in the bolt body by a sliding key, which locates in a groove within the rear of the bolt head assembly - when located and locked into the bolt head there is 2-3 degree's of rotation (nominal) when fixed.

The collets do not rotate when the bolt is cycled, neither does the bolt face - extraction is carried out by the extractor and plunger working as the bolt is drawn rearwards.


The case doesnt rotate during this phase or the firing phase.


Interesting point regarding the Lee primer - it may be this, but the grooves are pretty deep - you'd have to give the cases a shove in a tight fitting case holder (with a burr) to create the mark.


Can happen, I guess.


Be interesting to see what the eventual cause is.

:)
 
Thanks for this Redmist, I was sure I had read that even the Blaser rotates the head slightly to get extraction, but I could well be wrong on this as like you say I can't see how it can possibly do it.

The cases were new so I'm causing the scratches somehow. What it will need is me to get a new case and introduce it into the system and monitor its condition at each stage until it gets marked. I have a sort of feeling, which I can't support, that it is happening with the shell holder in my Lee hand priming tool. As you can imagine my main concern is that it isn't some obscure indicator of pressure. The cases have been reloaded, using this load, several times now and primer pockets are still tight plus as can be seen from the images there are no clear pressure signs. However on Saturday I shot one over the chrony and the velocity was, to put it mildly, remarkable. That caused me to step back and examine things again and these scratches were the only strange things I could find that were unusual, however I'm pretty sure they came into being with much milder loads.

Unlikely as any marks would be on the inside lip of the shell holder where the inside of the rim would be. What kind of trimming rig are you using? What ever you are doing it while the case is rotating; or so it would appear. The sure way to tell is to take a new (or unscarred) case and begin the loading process... not skipping a step. If the case makes it unmarred to the rifle, look to the bolt face for a radial tool mark.~Muir
 
I have a sort of feeling, which I can't support, that it is happening with the shell holder in my Lee hand priming tool.

Are you also using a Lee holder and cutter for trimming to length ?
I do, and have one case with the same marks, silly me decided to try trimming to length after neck sizing :doh:
This resulted in the cutter stud being very tight in the neck, and the case spun in the holder.

Neil. :)
 
Are you also using a Lee holder and cutter for trimming to length ?

That is exactly what I'm doing Neil, so perhaps Muir and yourself are correct. I haven't noticed the case turning in the trimming setup but then it might turn and not be very obvious. I have also noticed that sometimes the case can be "tight" to come out of my Lee hand priming tool, though it went in easy, and it sometimes turns as I remove it. This is not because the newly inserted primer is sitting proud so I cant explain what is causing it to be tight like this on removal but it is another possibility.

As Muir says I might put a new case through the process a few times, checking after each step, and see what happens, it is possible that these marks all happened a long time back and that their number is not increasing. In the past I had just dismissed them as something trivial but thought it best to ask just in case.
 
The only stupid question is .............................................................







The one never asked!
 
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