doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 2 3/4" shells in a 2 5/8" 16 gauge

I found a reference which I will post when it is uploaded, it shows the bore when marked 16/1 was 0.669 at proof.

I was incorrect when I stated undersized. I was thinking of 12 bores marked 13

That bore diameter provides a reference on barrel wear for you when measure it now

You really need to post a photo of all the barrel flat and barrel stampings in order to get input on shell size and likely pressure guidelines.

Going back to earlier posters a careful evaluation of the gun including all stamps, barrel wall thickness, action on face, style of lockup in order to provide a more competent opinion for type of ammo

The gun is at Bachelder for repair because it fired upon closing and double fired. As soon as I get it back I will post additioanl photos. In any case, I believe I will sell the six boxes of 2 3/4" 1 ounce 16 gauge shells bismuth shells. I am looking onto reloading some myself.

Hang on to them until the ones at Cabela's go off sale, Tom. They can be bought right now for $13.99/box.

SRH

The /1 always means it is a half size Bigger than the gauge ahead of the /. Nominal 16 is 662", 16/1 is .669". Up until actual diameters appeared this was normally checked with a series of plug gauges. Thus a bore marked 16 would accept the .662" plug but not the 669" one. A 16/1 marked bore would accept the 669" plug but not a 677" (15 gauge) plug. A 17/1 would be a half size under.

Great data 2-piper, thanks

Interesting, but why make different bore sizes for the same gauge?

The different bore size--as long as it isn't TOO different--doesn't make much difference as long as the chamber size is standard for the particular gauge in question. Barrels a little overbored or underbored? No big deal. But in the case of the Brits, they wanted to know and indicate the exact bore size on the barrel flats via the fractional (/1) marks. That's because, by their standards, a gun is out of proof if it's overbored enough to move it into the next gauge category. For example, if a barrel marked 16/1 (.669 standard) measures .677 or more, then it's a 15 gauge and would legally require reproof. The thinking is that if it's overbored too much, then the barrel walls may no longer be thick enough to pass proof. Someone got overly ambitious with a hone.

Bore dimensions and marks post-1887 Rules of Proof.
"At proof if a plug gauge of 0.729" diameter (but not one of 0.740") will enter the bore to a depth of 9", that barrel is at present marked .729" and under the 1925 Rules of Proof would have been marked 12."

Should be fine except out of a semi-automatic...

One point to ponder is when the 16 came out the hulls were made of paper which is thicker than plastic.

And if the paper hulls were thicker was the OD or ID different than a plastic shell?