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Tom_H
.333 member

Reged: 13/04/05
Posts: 336
Loc: Southeast, NY

Minimum Wall thickness for a .58 ml barrel?
#165015 - 26/07/10 11:28 PM

I have a .58 barrel blank that I:
-am not sure of the manufacturer
-Do not know the type of steel

I believe that it might be a douglass which would be good.

The question is about minimum wall thickness as I was hoping for 15/16 to rebarrel an existing gun.
I have never seen a 58 less than 1".

Thanks

Tom

--------------------
Carbonation without fermentation is tyranny

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fdsauer5116
.224 member

Reged: 15/07/10
Posts: 1
Loc: Texas

Re: Minimum Wall thickness for a .58 ml barrel? [Re: Tom_H]
#165045 - 27/07/10 10:07 AM

Tom,

unfortunately, it depends on the steel and its heat treat. The rupture strength of a gun barrel depends on the pressure of the load, the inner diameter (.58 in your case), the ultimate strength of the steel, and the wall thickness.

If you have or can get the Rockwell C hardness of the barrel, you can determine the ultimate strength of its steel. I'm not sure what pressure black powder loads can get up to, but someone should know that. Then a bit of engineering 201 and you have an estimate of the capability of your barrel.

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Bramble
.375 member

Reged: 29/07/06
Posts: 950
Loc: England

Re: Minimum Wall thickness for a .58 ml barrel? [Re: fdsauer5116]
#165059 - 27/07/10 08:52 PM

Respectfully

A hardness test will not be enough information to determine the yield point of that barrel. One would need also to know its chemical composition.

Further there are a number of steels that if incorrectly heat treated will give appropriate RC values but are subject to embrittlement if not heated or cooled correctly through certain critical points. 4140 for example is one of these.

If that information cannot be determined then it is far better to throw it in the scrap bin at this point.

Regards.

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DarylS
.700 member

Reged: 10/08/05
Posts: 27009
Loc: Beautiful British Columbia, Ca...

Re: Minimum Wall thickness for a .58 ml barrel? [Re: Bramble]
#165067 - 27/07/10 11:59 PM

Tom - I would not use a 15/16" Douglas barrel in .58.

Douglas used 12L14 which is leaded steel (fee machining), which is OK if thick enough and without any flaws. It is not gun barrel steel, although some companies make ML barerls from it. If the barrel was modern 'gun barrel' steel, I would use a 15/16" in .58. 1137 might be OK, but I'd rather have an inch across the flats or in diameter (at the rear 8" or so) for a .58.

A barrel that size would have to have a patent breech or drilled touch hole, not a drum and nipple or vent liner - too thin in my opinion.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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Tom_H
.333 member

Reged: 13/04/05
Posts: 336
Loc: Southeast, NY

Re: Minimum Wall thickness for a .58 ml barrel? [Re: DarylS]
#165086 - 28/07/10 10:40 AM

Thank you all for the replies.

I am currently waiting for a call regarding any markings on the breech of the blank which hopefully will shed some light on the composition. It is sitting in the back of a friend's Subaru.

I was going to make a drop in for a pre existing rifle hence the 15/16. Worst case I build another rifle and cut a wedding band to drop some weight.
The only rifle that I own that could handle the blank as is is an underhammer. That would make a nice hunting rig in itself and would be a bit less work than fitting to a hammer gun.
Thanks

Tom

--------------------
Carbonation without fermentation is tyranny

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DarylS
.700 member

Reged: 10/08/05
Posts: 27009
Loc: Beautiful British Columbia, Ca...

Re: Minimum Wall thickness for a .58 ml barrel? [Re: Tom_H]
#165117 - 28/07/10 11:40 PM

Tom - in my opinion, .54 cal. is at the upper edge for a 15/16" barrel - using a patent breech of course. Even at that size, I would hold my max loads to about 120gr. 2F GOEX.(which is suitable for any game we have in NA)
I have owned 3 .58's in the past that would not shoot accurately with less than 140gr. 2F GOEX. The larger bores do develope much lower pressures - but - recoil comes into it with light barrels = light guns.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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