Rough Chamber Question


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anapex
August 3, 2004, 05:40 PM
I have a K98 Mauser that seemed to be stretching the casings, I had my smith look at and he says it's still ok to shoot and that it looks like the cases are stretching because it's forming to the roughness of the chamber. Would a rough chamber make a case look like it's been stretched? It's near the rear of the case that's why I'm wondering.

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ocabj
August 3, 2004, 06:23 PM
Got any pictures of the cases?

Did the smith or yourself check the headspace of the rifle?

anapex
August 3, 2004, 06:42 PM
I'll try to get some pictures of the cases. The smith checked the headspace not me.

Redlg155
August 4, 2004, 02:35 AM
Try checking this article out...

http://www.reloadingpro.com/Inspecting%20the%20Brass.htm

Lots of good information there. If it is just a rough chamber and not a headspace problem I wouldn't worry about it if it doesn't interfere with normal functioning and you aren't using it for an "emergency" rifle. If it really bugged you, then you could always polish the chamber.

You problem sounds like a bit of a headspace problem.

Good Shooting
Red

anapex
August 23, 2004, 06:48 PM
OK I finally took some pictures of the cases I save so here they are along with what the gunsmith told me.

http://img.photobucket.com/albums/v395/anapex/8mmheadspace2.jpg

http://img.photobucket.com/albums/v395/anapex/8mmheadspace1.jpg

They smith had a go gauge, a no go gauge, and what he called a field gauge. Both the go and no go gauge would close on the gun, the field gauge which was slightly longer then the no go would not close. The smith told me that the gun was still shootable and that the markings on the cases were from it fire forming to a rough chamber. The chamber looks like it has some light pitting ( I would have a had picture of it but man it's hard to get a camera in there good enough).

rbernie
August 23, 2004, 06:52 PM
Hmph - I always thought that the 'no-go' guage meant exactly that... ?????

TimRB
August 23, 2004, 07:25 PM
Here is a link for a short article on checking headspace:

http://www.rifleshootermag.com/gunsmithing/headspace_0612/

The author says that while a bolt should not normally close on a no-go gauge, the rifle may still be satisfactory if it closes on the no-go but refuses to close on the field gauge.

I guess this guy knows what he's talking about, but if I had a rifle that closed on the no-go gauge, I'd get it fixed or stop shooting it.

Tim

ocabj
August 23, 2004, 08:02 PM
Did you use a digital camera to take this pictures? Use the macro setting next time. The pics are a little too blury to see details.

Anyway, a bolt that closes on a no-go gauge but not on a field gauge is OK to fire. The only problem you are going to have is that it's going to be rougher on the brass since it's going to expand more than it would on a shorter headspaced chamber. If you plan on reloading, then you would definitely only want to neck size to lengthen brass life.

BTW: When you headspace a gun, you should be sure to use only fingertip pressure. Use one finger to close the bolt. The bolt should move very very smoothly and once you feel any kind of resistance, STOP. You can make a bolt close on a no-go gauge even though the headspace is good if you put enough force into closing the bolt, and sometimes, the force doesn't need to be very excessive.

Jim K
August 23, 2004, 08:32 PM
I have seen cases from that rifle and think it does have a headspace problem, though perhaps not yet to the danger point.

There is an easy way to check. Cut a case in half lengthwise with a hacksaw. Look to see if there is a depressed ring of brass inside in the same place as the shiny area on the outside, indicating that the brass is thin at that point. If there is (and I think you will find there is), the case is being thinned from stretching due to excess headspace, not merely being marked by a rough chamber.

What happens in a rifle chamber is that when pressure builds up, the thin forward part of the case expands outward and seals against the chamber walls. This is called "obturation" and is what keeps that high pressure gas in its place, and not coming back at the shooter.

But the rear of the case is solid and cannot expand, so it tries to back up, stretching the case. This happens about all the time, with every rifle and ammunition. Normally, the case will not stretch beyond the elastic limits of the brass, but if the rifle has excess headspace that elastic limit is exceeded. That is what is happening here, as shown by the bright ring of stressed brass.

If the headspace becomes more excessive, the case will actually be pulled (or actually pushed) apart and the head will separate. At best, this results in a stuck case which has to be removed; at worst, high pressure gas is released into the action damaging the action and, perhaps, the shooter.

Is the rifle at the danger point? I don't know, but it is not right, IMHO. If the cases are discarded, the problem can perhaps be ignored, at least for a while. But reloading such cases will further stress the brass and hasten case failure.

Jim

Vern Humphrey
August 23, 2004, 09:23 PM
Quote:
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The smith had a go gauge, a no go gauge, and what he called a field gauge. Both the go and no go gauge would close on the gun, the field gauge which was slightly longer then the no go would not close.
--------------------------------------------------------------

You have a headspace problem. The "Field" gauge was a military expedient -- to see if a rifle was dangerous to fire. If the bolt closed on a field gauge, the rifle was immediately taken out of service. NOT closing on a field gauge does NOT mean the rifle is safe to fire!! It only means that a militarily acceptable level of risk is present.

The best solution to the entire problem would be to run a .30-06 chambering reamer into the chamber, converting your rifle to 8mm-06. This would also clean up some of the roughness of the chamber (a little polishing might also be desirable).

You make cases simply by necking up .30-06 cases, and have a fine cartridge with a bit more potential than the present 8X57mm round.

anapex
August 23, 2004, 09:47 PM
I'm not sure if I could convert the rifle to an 8mm-06 if I wanted to. It was purchased with my C&R FFL so I'd have to look up how legal it is to change the chambering of a firearm purchased with it. If I can though I might just do that.

TimRB
August 24, 2004, 10:47 AM
"I'm not sure if I could convert the rifle to an 8mm-06 if I wanted to. It was purchased with my C&R FFL so I'd have to look up how legal it is to change the chambering of a firearm purchased with it. If I can though I might just do that."

That, at least, is not an issue. If you make the rifle a non-C&R by altering it from its original configuration, you can just transfer it to yourself in your bound book, as in a private party sale.

Tim

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