doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com choke measurement questions

Not at all unusual to get two different bore diameters, right from the factory--no honing involved. You'll see the same thing noted above on older Brit doubles too, but with the old British "gauge" proofmarks. Like 13/1 on one barrel, 12 (or 13) on the other.

A bore mike is indeed an essential piece of equipment.

I agree with Miller, the one marking is for bore and if two the smaller number would be for choke.
I'm guessing the Spanish markings would be the same, in metric. They used * for their choke system, but used mm for bore size. Zabala 12 ga has *** = imp. cyl., 18.5 =.728. right barrel and ****=mod., 18.5=.728. left barrel. Both bores with gage are .728 and chokes come out as indicated with the * markings.
Another Zabala 28 ga has *** imp.cyl., 13.8 = .543.right barrel and ****=mod.,13.8 =.543. left barrel.

18.5 mm is .7283465= .728 and 28 ga. 13.8 is .5433071=.543

WTS, maybe this would work

Jim

You guys are wonders. Thanks.

Based on a Belgium proofed 16ga. I have, I agree with two numbers on the same barrel being bore and choke.

Mine is stamped 17.0, or .669 inch on both barrels. The left barrel is stamped 16.4, or .645 inch, over the 17.0 and the right barrel has only the 17.o. The right barrel is, in fact, bored cylinder and the left is choked full using an inside micrometer with a 3.5 inch reach.

I had an old Arrieta that also had two numbers, bore and choke.
Around here, the use of * for choke is a recent convention for choke marking, with a lot of people using 1/10ths of mm as a more precise way of describing the given choke.
M&M gun has 6/10 mm in the left barrel and none on the right.