Rough chamber

Ammunition, reloading, shooting, etc
Hamish
Posts: 94
Joined: Thu Jun 01, 2017 11:18 pm

Re: Rough chamber

Post by Hamish »

Those marks on the fired brass make me think steel wire brush spun by a drill,,,

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butlersrangers
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Joined: Wed Oct 07, 2009 11:35 pm
Location: Below the Bridge, Michigan

Re: Rough chamber

Post by butlersrangers »

'Misanthrope' measured his barrel's length and rear-sight hole location.
His findings would indicate that the barrel has not been 'set-back'.

Another speculation: Maybe this Krag was once deactivated (DEWAT) for some purpose, like "Drill Rifle", and had the chamber blocked with some welding material.
Possibly, at a later time, someone tried to re-cut and clear the chamber, leaving irregular tool marks?

An interesting mystery!
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rough-necks.jpeg
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FredC
Posts: 1991
Joined: Fri May 31, 2013 4:38 pm
Location: Dewees Texas

Re: Rough chamber

Post by FredC »

butlersrangers wrote: Sun Dec 13, 2020 6:44 am Another speculation: Maybe this Krag was once deactivated (DEWAT) for some purpose, like "Drill Rifle", and had the chamber blocked with some welding material.
Possibly, at a later time, someone tried to re-cut and clear the chamber, leaving irregular tool marks?

An interesting mystery!
That was going to be my next guess, tool marks indicate a revolving cutting tool. Could have been drilled on a lathe or a hand drill used.. On the cartridges that were inserted and not fired I thought I saw a rifling mark on the slugs. It would be interesting to do that again with the slugs marked up to show up any marking. A drilled out weld would not necessarily follow the centerline of the old chamber.
BR and I are still guessing. One other possibility is some damage from repeated spit necks and an attempted repair be spinning some very course sand paper. Forensic Bubba investigation!

misanthrope
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Joined: Sun Jun 14, 2020 3:59 pm

Re: Rough chamber

Post by misanthrope »

I did notice that the firing pin marks were slightly off-center on the primers but didn’t think much about it. Looks like this rifle will be a “safe queen” until I can replace the barrel.

misanthrope
Posts: 11
Joined: Sun Jun 14, 2020 3:59 pm

Re: Rough chamber

Post by misanthrope »

Image I managed to get a photo of the inside of the chamber. I can’t imagine what happened here.
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82E379DE-0C6D-4E0A-A1BB-EBE9911E4D41.jpeg
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FredC
Posts: 1991
Joined: Fri May 31, 2013 4:38 pm
Location: Dewees Texas

Re: Rough chamber

Post by FredC »

Sure looks rough, but the focus is still a problem understanding what is in there. I think the earlier conclusion to make it a wall hanger or safe queen till you get another barrel is the best plan. BR had a thread about changing barrels recently, it can be done by a one that is mechanically inclined. Installing a new Criterion barrel involves reaming and fitting special screws that adds a couple of extra steps.

Doing a cast of the chamber could maybe tell you more but it probably is an extra expense on a barrel that is probably a lost cause.

Crooked Horn
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Joined: Wed Mar 17, 2021 8:47 pm

Re: Rough chamber

Post by Crooked Horn »

It looks like debris or corrosion is adhered to the surface of the chamber and is scratching the case neck as the cartridge is turned out of battery by the bolt after firing. Are the case markings indented into the brass or raised from fire forming into deep scratches in the chamber? What does the bore look like? You could try lightly polishing the chamber with steel wool wrapped tightly around a bronze bore brush with cutting oil (chucked in a drill), or fine sandpaper on a mandrel. Then do a chamber and throat cast to see if it is oversized too much. You can have the barrel set back and rechambered if so, no need for a new barrel unless your bore is bad. My Krag barrels are parallel OD for 2.5 inches or so ahead of the receiver, and so could be set back and rechambered several times if needed. You need an expert smith to do this work.

misanthrope
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Joined: Sun Jun 14, 2020 3:59 pm

Re: Rough chamber

Post by misanthrope »

61A9952B-5EAD-4A49-BF9D-DA13385B8EE6.jpeg
61A9952B-5EAD-4A49-BF9D-DA13385B8EE6.jpeg (390.04 KiB) Viewed 1639 times
Update: I ran a 400 grit Flex Hone into the chamber and all but a trace of the marks disappeared. I will finish it off with an 800 grit.

Zac952
Posts: 159
Joined: Wed Apr 07, 2021 1:37 am

Re: Rough chamber

Post by Zac952 »

Looks like you may have gotten rid of the marks, it may be worthwhile to get some Cerrosafe and cast the chamber to measure the neck diameter, removing these marks could have taken off too much material in the neck area, likely it would be OK, but with too loose of case neck your brass will be working excessively- mainly a problem if you reload, but also this is where you case will obturate, it will also obturate on the shoulder and then the rim area but with gases blowing back down the neck it will cause erosion over the long run. This could also cause split necks on the first firing if it is too large and that will also erode the chamber.
You may be alright but I would cast it just to see, casting will also give you insight into groove diameter, rifling condition, and other chamber conditions possibly overlooked. By the way 1 lb of cerosafe can be used over and over, until you either lose it or turn it all to slag on your ladle from hundreds of chamber casts,
How much is too oversize to be safe? That is out of my league to answer, but I'm sure someone here will have a approximation for that.

Zac952
Posts: 159
Joined: Wed Apr 07, 2021 1:37 am

Re: Rough chamber

Post by Zac952 »

Also I'll bet this was caused by a case neck that broke off into the chamber and someone attempted th thread a screw into it to remove it, the proper way would be to use cerosafe to cast and then tap out your casting with the stuck case neck. Just a guess

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