Need Dimensions of a Ten Gauge chamber

[Roswell 1847]

I have a very old hierloom shotgun that is in 12 gauge. Its barrel is much thicker than any 12 gauge barrel I've ever seen.
I've already reamed the bore out to .745 in an effort to remove deep pitting but some remains.
I've been told this gun was built on a Ten gauge frame and the barrel was made so thick because they often "Freshed" out the bore to Ten Gauge if it got very pitted.

The barrel walls at the bore are plenty thick enough but Im not so sure about the chamber walls.

The gun is good and tight, after I made a replacement taper pin and wallowed the pin hole a bit to set it back a hair. The original taper pin had been lost long ago.
I also made a buttstock from a broken double barrel stock of the same vintage.

Anyway I haven't found a site with ten gauge chamber specs yet. I'd like to check these out before investing any more time and effort in this.
Could be I'll have to sleeve it to a twenty gauge or better yet a sixteen gauge.

[gp911]

If it is very old you don't want to ream it for modern 3.5" 10 gauge shells... Even the older 2-7/8" loads could be too much for it. There is the possibility of loading your own for it, but I think the sleeve idea may have a better chance of success.

YMMV,

gp911

[Roswell 1847]

Right after I posted this I found a site with chamber dimensions.

http://www.dave-cushman.net/shot/shotshellloads.html

The Ten gauge chamber is only about .04 larger than the twelve gauge chamber.
It looks like there would be plenty of meat left if I chose to rebore and rechamber. The old gun must have been built on a ten gauge frame afterall.

I agree that only shells eqivalent to the late 19th century loadings should be used.

Examining the bore once more I can see that the remaining pitting might polish away leaving an oversize bore still within maximum limits for good shooting with the 12 gauge.
At least this way I'd be more sure of not generating as much pressure as with a standard diameter bore.
Maybe I'll tie the old girl to a stump and testfire it using some light low based loads. If it don't blow up I'll just hang it on the wall.

I've read of some very light short cased loads being available these days, maybe I'll try some of those out.
I've read of English bird guns that used a very short lightly loaded twelve gauge that threw about the same amount of shot as a 28 gauge, and very trim short chambered doubleguns made just for those loads.

[2RCO]

Don't do it! If it is that pitted then their could very well be subsurface rust that would likely weaken the barrel and make it highly dangerous.

Also--Please tell me it is not Damascus.

[ArchAngelCD]

Roswell 1847,
Like you said, polish out the rest of the problems in the bore and don't remove any more material from the inside of the barrel. If you find that you have an accuracy problem you can always tap the front of the barrel to accept choke tubes. Then you can shoot any type of 12ga shell you want.

[Roswell 1847]

Also--Please tell me it is not Damascus.
Nope definitely not a Damascus barrel, though it might be what they called Twist Steel which was a process where the barrel blank was heated and twisted to force any microscopic impurities in a concentric formation rather than lengthwise. Confederate Carbines like the Murray were made this way.

The remaining pits are all on the upper inside surface. I figure it was hung upside down for years ans moisture gathered there by gravity causing more rusting there. The pits look broad but shallow. Theres no pitting near the chamber so if the pressure curve drops rapidly beyond the chamber there would be less pressure anywhere near those pits.
In fact if I wanted to cut the barrel back to 22 inches or so I'd eliminate all but a couple of the smaller pits. I might end up doing that, theres no collector value left to this one as it is, even the company name disappeared while sanding away all the rust.

The barrel walls are several times thicker than those of the stoutest modern shotgun barrels I've ever seen.

The gun looks just like photos of the Davenport Single Barrel guns. These were made in large gauges up to 8 bore. A very strong action type.

[JohnBT]

"it might be what they called Twist Steel"

That could be worse/weaker than a good Damascus barrel. It all depends on the original quality and the current condition.

John

[berettashotgun]

Is it a Parker?
Twisted steel barrels were fairly common (the only type!) on their shotguns that I have looked at; those made around the time of my 1877 10ga.
A simple ultrasonic tube inspection performed at an oilfield tube inspection place will easily verify the barrels integrity. Aircraft places charge too much (guess what I do):neener:
That stated, I'll bet they ain't no good. The reason is the oxidation occurs between the wires at the point the "twisted" ( it should be called "wrapped" )wire is fused. Twisted wire barrels are a novel approach to Damascus, instead of sheets of steel it used wire (duh) wrapped around a mandrel that was then hammered into the form of the barrel.
A sleeve would be the way to go IF you want to use the shotgun without any reservation, a 16ga would be neat. That's the direction I'd go, but that is just the way I am.

[Roswell 1847]

I think we are talking about two different forms of Twist steel barrels.

Twisting the heated barrel blank was a process developed by the Confederacy for making gun barrels with lower grade steel or iron. It works by forcing any impurities that aren't brought to the surface into an orientation concentric to the bore rather than longitudinal. This prevented barrels from splitting. The barrels for JP Murray Carbines were made this way.

The barrel looks far to thick to have been formed around a mandrel. It looks more like it was Twisted into a short blank then drilled and finished by cold rolling in the way that US musket barrels were produced. Various sizes of mandrels were slipped into the short blanks then the blank was rolled between heavy rollers with progressively smaller diameter grooves. The barrel became longer and slimmer with each pass. The barrel was then straightened an the bore finish reamed. If meant for a rifled musket it would then go to the rifling jigs.