Just aqquired a 20 ga back action drilling and was really supprised that it was a 20 x 20 x 9.3
circa. 1890's and it got me wondering when the 20 was introduced?

m4220

M4220,
I would be very confident that the 20ga. bore goes back to the days of black powder muzzleloaders and flintlocks. It is a standard bore diameter designation that preceeds what we know as a shot shell.

20ga. simply means that a lead ball the diameter of a 20ga. barrel weighs 1/20th of a pound. That is it takes 20 of those lead balls (.617" dia.) to make a pound. For a 12 ga., it takes twelve .729" dia. round lead balls to make one pound and that is the size of a 12 bore shotgun.

The old shotguns were made in a whole host of diameters from 2 gauge (a bore the size of a half pound lead ball) down well beyond 32 gauge. See Wikipedia for a listing of barrel sizes and gauge equivelants. http://en.wikipedia.org/wiki/Gauge_(bore_diameter)

The historical origins of the 20 gauge is very probably lost to antiquity. I doubt that anyone knows why guns were made in 20ga. and not 18ga. or 22ga.

quote:

I doubt that anyone knows why guns were made in 20ga. and not 18ga. or 22ga.

I am not so sure. Certainly the 38 S & W exists only because it is the same weight bullet as a .44 calibre black powder round ball.

The 12 bore was the same size as the British "Brown Bess" musket and the 16 bore...well clearly a one ounce ball is easy to weight...and was the same bore as the French musket.

Railway lines? 4' 8 1/2"? The same gauge as a roman chariot apparently, which then was adopted by farm carts, which then was used for the wagons in factories in England, which the first train was built to tow, which when the lines spread further out from the town stayed the same!

So there will be somewhere at sometime a reason for 20 and not 18 or 22. Five pounds of lead gives 100 balls? And perhaps the ingots of lead were cast into five pound ingots? Maybe. Maybe not.

But somewhere there will be an obvious reason to the people at the time even though lost to our knowledge today.

enfieldspares,
Yes, at some point in time someone did have a reason for building a smooth bore gun in the size of a lead ball 1/20th of a pound. Some historian may be able to point to one gunsmith who started building twenty bore guns and the reason why. It would certainly be interesting if one could.

Still the 20 gauge shotgun that we know probably can't have been said to have been introduced like we say the .357 Magnum, .45 ACP or .500 S&W were introduced. The cartridge (or shell) came many decades if not centuries after the 20ga. became a standard shotgun boring.