12ga barrels question

[Roberto S Siciliano]

I have an opportunity to buy a PB 12ga hammer gun circa 1888. The owner says the bore at the muzzle end of the barrels is large like a 10ga muzzle. He's not shotgun friendly and I'm trying to figure out if the barrels have been re-bored along the way or if there was such a PB gun made that was bigger at the muzzle.
I might be able to pick up the gun at a good price but if the barrels have been tampered with, I'm not interested.

Any thoughts about this are appreciated.

[Dean Romig]

Without a bore mic and a wall thickness gauge you’d only be guessing and buying it might prove more costly than “a good price.”





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[Garry L Gordon]

I don’t know where you are, or if the seller would agree, but if there was a more experienced member near you that could help you evaluate the gun, that might be a good option.

[Roberto S Siciliano]

So here's what I found out.
The wall thickness at the muzzle is 1.32mm [0.0519685"].
The left barrel gauges at full choke. The right barrel is in the 10ga range. Could this be factory... or was the right barrel re-bored. Is 0.0519685" muzzle thickness acceptable?
Photos are attached.
Comments appreciated.

Without a bore mic and a wall thickness gauge you’d only be guessing and buying it might prove more costly than “a good price.”





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[Brian Dudley]

It is not too uncommon. I recently had a 12g C grade hammer gun in my shop with 10g boring. Built that way.

[Roberto S Siciliano]

96860

96861

96862

[Roberto S Siciliano]

Is a wall thickness of 0.0519685 [1.32mm] at the muzzle acceptable for firing, assuming there is no serious pitting?


It is not too uncommon. I recently had a 12g C grade hammer gun in my shop with 10g boring. Built that way.

[Garry L Gordon]

Drop in gauges can be very deceiving in regard to wall thickness at strategic points along the length of the barrels. The only good way to ascertain the wall thickness is with a gauge that can be put into the barrels far enough to measure their entire length from both muzzle and breech.

[Milton C Starr]

I have seen quite a few Parker 12 gauges for sale with bore diameters in the .750" range and 10 gauge Parkers with bore over .800" so you cant go by bore diameter exactly . Seems like on old American doubles they usually run a bit bigger on bore sizes and on English guns they run a bit narrow . It should be noted SAAMI specifications didnt start until 1926.

[Roberto S Siciliano]

Thank you gentleman. Your contributions are exponentially contributing to my learning curve.
Much appreciated.

[Dean Romig]

So here's what I found out.
The wall thickness at the muzzle is 1.32mm [0.0519685"].
The left barrel gauges at full choke. The right barrel is in the 10ga range. Could this be factory... or was the right barrel re-bored. Is 0.0519685" muzzle thickness acceptable?
Photos are attached.
Comments appreciated.


The wall thickness at the muzzle is not where you need to take measurements for safe shooting. Barrel wall thickness to determine minimum wall thickness must be taken along the entire lrngth and circumference of each tube. Thin spots can show up anywhere. Thin spots can also support a suspicion that barrels may have been honed.





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[Brian Dudley]

Leave that drop in gauge in the drawer if you are dealing with any Parker made before the 1920s.

[Roberto S Siciliano]

Got it!
Thx


Leave that drop in gauge in the drawer if you are dealing with any Parker made before the 1920s.

[Dave Noreen]

Parker Bros. guns made in the 1870s and 1880s are well known to be seriously over-bored. I have an 1889 12-gauge that mics .757".

Ammunition loading companies offered special shells for Parker Bros. guns with a size larger wads. See Loads No. 56 & 57 --

96868

96869

[Dave Noreen]

Duplicate post