doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Help with proof mark cypher

How do these proof marks relate to marks that indicate 1, 1 1/8, 1 1/4oz. maximum shot load. This is a Boswell Live Pigeon gun, with 2 3/4" chambers so I'm thinking it should be the equivalent of 1 1/4oz. max. Am I wrong?

Must say that I do not see any indication of shot weight among these proof marks. Believe that the 2-3/4" chamber length suggests that 1-1/4 oz of shot is what the gun was reproofed (crown over R) for in London in 1978 (as the LP78 stamp indicates). Need someone more knowledgeable to chime in.

Regards, Tim

Looks like original marks were for black powder .1978 London reproof at .740" so bored up from .719" nominal [ you never actually know what the bore size was when submitted] 2&3/4" chamber so 1&1/4 oz shot .Original chamber length unknown but due to age fair to assume 2&1/2" unless it is a heavy pigeon or wild fowl gun .

As Gunman says, 1 1/4 oz of shot.
However the acceptable shot load is only relevant to CIP cartridges. In some Mega-High, LongBrass, FarKiller cartridge with 1 1/4 oz load, the pressures may be much too high so please select your ammunition with care.
This is the joy of living in a CIP regulated environment: if it says 2 3/4" on the box you are good to go!
Also one should bear in mind that what the gun was reproofed for is not necessarily what the ancient wood and black powder designed action will take happily over multiple shots. The odd shot may be fine but the pounding provided by a round of clays may do real damage.

Under the 1925-1954 Rules of Proof, the 2 3/4� 12g max. service load was 3 3/8 Dr. Eq. with 1 1/4 oz. shot, with a mean pressure of 3 1/2 tons = 10,640 psi by Burrard�s conversion. (Primarily for heavier �Waterfowl� guns)

Major Sir Gerald Burrard, The Modern Shotgun, Volume II, �The Cartridge�, 3rd Revised Edition in discussing shotshell pressures for 12g 2 3/4� 1 1/4 oz. 3 1/4 Dr. Eq. stated "Standard Service" 9,296 psi; "Maximum Service" 11,984 psi.

The 1954 Rules of Proof �Highest Mean Service Pressure� equivalent transducer values as converted from LUP by Burrard�s formula 3 1/4 tons = 9,800 psi = 676 BAR. "Standard Service Pressure" for most loads however was about 8000 psi per John Brindle in The Double Gun Journal, �Black Powder & Smokeless, Damascus & Steel�; Volume 5, Issue 3, 1994, �Some Modern Fallacies Part 5�, p. 11.

The CIP transducer �Maximal Average (Service) Pressure" for 2 3/4" chamber or 3 1/4 tons is 780 BAR = 11,313 PSI

The gun weighs 7 lbs.14oz. It has side clips and a hidden third fastener, and a wide flat filed rib.(Pigeon gun?) steel barrels with a minimum wall thickness of .28 and .29. It's a hammer gun.
I'm thinking 2 3/4in. 1 oz. 2 3/4 dram. eq. at 1185 fps should be OK. Any disagreement with that? Gun is tight and in excellent overall condition.

The Hurlingham max weight for a pigeon gun changed for the 1881 season to 8 lbs. It changed again for the 1882 season to 7lbs 8oz. That's not to say that other clubs didn't allow heavier guns....but wondering if this gun weighing 7lbs 14oz was made for the 1881 season? Is it possible to be that old?

The gun was made in 1901.