doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com How to tell 2 1/2" chambering from 2 3/4"?

A friend of mine picked up a decent 12 gauge Greener with 26" barrels at a local gun show for $400. Apparently, somebody had just sold it to the seller for $250. Odd things happen I guess. Greeners seem to go for somewhat higher prices on Guns International, I've noticed.

It has older British proofs and the flats say "Not for ball," but there is apparently no mention of the chambering. Is there any way to tell without access to a gunsmith?

He sent me this photo:

QUICK way, roll up a 3x5 index card and insert into the chamber, see how far it sides in with out due force.

Second way is to use a chamber gauge

Third way is to check the proof marks more closely and then assume it
is 2 1/2 " chamber or even 2 " chamber


Mike

Not scientific at all, but I have used a fired 2 3/4 shell as a proxy for a chamber gauge on suspected 2 1/2 inch guns. On the guns that I had "tested", that appeared to indicate original 2 1/2 chambering.

You can just stock a tape measure straight in against the wall until it hits the front. Note the measurement as where is comes to the inner lip where the shell brass rests.

Where you really need a gauge is in checking chokes.

- NDG

A chamber gauge does come in pretty handy. Not very expensive.
But in the case of that Greener . . . being marked "not for ball", that would make it a 19th century gun. Too old to have the chamber length stamped as one of the official proofmarks. (That didn't happen until 1925.) But on a gun that old, the gun would almost certainly have left the factory with 2 1/2" chambers . . . although there's always a possibility, on older guns you find here in the States, that they have been lengthened to 2 3/4". 2" wouldn't be possible. The 2" 12 came along later, well into the 20th century.

I just answered this same question in the current "Chamber Length" thread, and explained why I much prefer Miller's oft recommended use of a simple inexpensive 6" machinists scale over 3" x 5" cards, fancy brass tapered chamber gauges, or fired shells. You can read that reply in my post here:

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=538330#Post538330

As you can see from this illustration of a 12 gauge chamber, the length of the chamber is from the breech end to the transition where the forcing cone begins:

Also look for the specific words stamped on the barrel flats,
NITRO PROOF.
If not there then it is a black powder gun & will have the crossed halberds mark in conjunction with the not for ball. Not for ball indicates a black powder proof unless the gun was reproofed & re stamped accordingly.

O.M

That's definitely and older Greener. You need to have the chambers and barrel wall thickness measured properly. Then use loads appropriate for a gun of that vintage. Don't half ass it.

A 6" machinists scale works as reliably as anything I have found. It is repeatable. Been using that method for many years.

Good reminder on having the BWT measured, tho'.

SRH

Whether it is "Nominal" 2�" or 2 3/4" actually has little to do with its age or whether it has only black or smokeless proof as well. Many nominal 2�" British guns, in reality, had either 2 9/16 (65mm) or 2 5/8" (67mm) chambers. What actually determined the chamber length was the gun's intended purpose. Game Guns normally had the short chambers, with Pigeon or waterfowl having longer chambers, up to as long as 3�" (82.5mm). I recall Nash Buckingham mentioning using a Greener hammer gun of his father's back in the 1880s which had 3�" chambers.

Larry was correct that the chamber length was not marked at that point. Measuring it will tell you what it has "Now". If the gun weighs in less than
7 lbs the odds are it started life with the shorter chambers even if they are longer now. I don't recall for certain when the 2" chamber was introduced, but don't think it goes back far enough to have been used in a gun stamped "Not For Ball".

I highly recommend the 6" flexible scale method. You cannot accurately "Feel" the start of a normal cone, but you can hold the barrels up to a light source, not overly bright though, & looking through the bore measure to the shadow line keeping the scale along the inner wall & where you can see it.