doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com A couple of proof questions (British guns)

Assuming a gun proofed with an original bore diameter of .649, what measurement would put gun out of proof (as far as bore diameter)?

Would the words "Nitro Proof" stamped on the barrel flats date a gun to any particular range of years, or has this been used on all nitro proofed guns?

.659 will be out of proof.Take the measurement 9" from the breech.

'Nitro Proof' was initiated as a proof mark in 1896 and discontinued in 1954.

Other marks used in tamdem will be of more help with dating.

Is the bbl stamped .649 or 17; or both?. .649" is the nominal dia of a 17ga bore, but if it has the .649 mark stamped in the bbl, then I believe it would have been proofed, or re-proofed, after 1954. I could be wrong, but I thought .008" (2mm) enlargment was considered the limit before a gun was out of proof. Originally it was when it would accept the next up plug gage size(17/1-.656") to the depth of 9"s.

Here are the proof marks. It's a 16 bore from Cabela's gun library.

http://s138.photobucket.com/albums/q241/stevenc131/?action=view&current=CFrancis16.jpg

I gather chamber length was added 1925,which probably means it will haver a small datecode on it as well.

GDU

1925 rule Birmingham marks. There is a date code present, but the photo is too poor to read it.

Left barrel ahead of the birmingham mark?

According to the rules of 1925, 17/1 starts at .655.

Larry is right 17/1 is .655". I simply averaged the 17 & 16 sizes & rounded to nearest .001". As soon as I read Larry's post it hit me, on these sub gages one doesn't "Round" but simply drops everything past 3 digits. The whole gauges themselves are always rounded to 3 decimal places.

Crossed swords on the outside corner of the breech end of the left barrel flat. Will be a one or two letter code in the angles.