doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Proof shot weights ?

What is the truth with shot weights in the proofs of British guns.
I have always believed that if my gun is proofed for 1 1/2 oz then I can shoot up to & including 1 1/2 oz of shot.
Like wise if my gun is proofed at 1 1/8 oz it includes 1 1/8 oz but not more. Same for 1 1/4 oz.

Why do I then see some say to keep under the 1 1/2 oz or 1 1/4 oz proof weight ? eg. Would they only shoot 1 1/8 oz in a 1 1/4 oz gun ?
Was that gun not shot at the proof house with a double charge & then deemed to be safe to shoot at the stamped weight ?

I have a 1925 British pigeon gun 3" chambered with a proof shot weight of 1 1/2 oz.I know enough to not shoot 3" magnum loads in it because the old 3" live pigeon load was a lot lower pressured load.
But that gun will eat any modern 2 3/4"load, right ?
O.M

From practical point of view this is tied to original mechanical condition of the gun, chamber length and the WEIGHT of the firearm. For 3" gun shot weight was 1&3/8-1&1/2oz with corresponding gun weight of 7&3/4-8&1/2lb. For gun between 7&1/4-7&3/4lb maximum of 1&1/4oz shot charge should be used. The cartridges with C.I.P proof standards should be employed not some US made Turkey or super duper pheasant loads. In USA we play with lighter payload weight and lower velocity numbers when matching US cartridges for our European guns.

In America if one has gun like yours we go to closest places that carries cartridges (usually place called Wallmart where they don't sell wall paneling or wallpaper but sell food and many other every day things) and buy few boxes of Federal Game-Shok, Winchester or Remington 1 oz or 1&1/8oz load at avg. vel of 1250+/-50fps and go hunting. No Turkey, Wildfowl or crazzy Pheasant loads like NitroMags or Praire Storm,....

No. US (SAAMI) pressure standards are the same for 2 3/4" and 3" 12ga. And the maximum standard service pressure for American 12's is higher than that for vintage British guns. You'd be OK if you had a Brit 12ga with the CURRENT superior (magnum) proof. But not with that gun. One reason the British proofhouses changed from the 1925 rules to the 1954 rules (the ones that used "tons per square inch") is that between those two dates, British ammo makers had begun producing higher pressure loads which weren't available when the 1925 rules of proof were established. Prior to that time, all British 12ga 1 1/8 oz loads, for example, were OK in any British gun proofed for 1 1/8. That had actually changed before WWII with the appearance of hotter loads, but they didn't get around to modifying the proof rules until after the war.

What is the avg. pressure difference between say NitroMag 2&3/4" and easier on shoulder standard game load of 1 oz or 1&1/8 load with published muzzle velocity of 1250+/-50fps? Many standard US made game loads sold in USA are also sent into EU, therefore, the box contains CIP monogram with M designation which probably means CIP Magnum. Walmart stopped carrying Pomi tomato juice and now carry some kind of Hunts or Italia Brand , but I did manage to score several boxes of very easy on shoulder leisure time target loads 12ga 2&3/4" 7/8oz 8shot with velocity of 980fps. My uneducated guess as to pressure for these would be around 7000psi. I wouldn't use those to hunt upland birds but for backyard clays round these should be good especially out of 6.5lb game gun with checkered wooden butt plate.

It is also noted that the British loaded "Low Velocity" with 1� oz of shot with pressures no higher than the standard 1 1/8 oz load which were suitable for use in a 1 1/8 oz proofed gun. Confusion over this was one of the reasons for changing from the shot weight to Tons proof. The old 1 1/8 oz proof was essentially the same as the later 3 ton proof I believe. The actual shot charge weight is not the important factor, but rather the Pressure of the load.

Now we are getting somewhere.
I know that the old 3" pigeon loads were a lot of wad in that length & also not a really high pressure load.
So, what sort of pressure would those old 3" 1 1/2 oz loads be ?
This would give me a real figure comparative to modern loads.
O.M

Moses, the problem would be that if you could get a pressure figure from period literature (where's Drew when we need him?), the pressure would be as measured by lead crushers rather than the current piezoelectric method. You come up with a figure that's like the old LUP (lead units pressure) that you used to see in old reloading manuals. You can't get an exact conversion, but you can guesstimate close enough to get you into the ballpark. And then back off some to build in a safety cushion.

British 12g 3" 1 1/2 oz. (1925 Rules of Proof "Maximum Service Load") 4 Tons (1954 Rules of Proof �Highest Mean Service Pressure�) would be 12,320 psi by Burrard's conversion to piezo trandsducers, or 11,917 psi by piezo transducers per the Birmingham Proof House...or something like that

Note the 3" SAAMI Max. is the same as 2 3/4" at 11,500 psi

1925-1954 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)

Turn-of-the-century U.S. 3" or even 3 1/4" Pigeon loads were limited to 1 1/4 oz. 3 1/2 Dr. Eq. BULK Smokeless at about 11,750 psi /
1 1/4 oz. 3 1/2 Dr. Eq. DENSE Smokeless at about 12,600 psi

Hmmm. Those old shells weren�t exactly �low� pressure were they Doc Drew? :-).

Thank you for all the awesome info you post, you�re a real scholar.

To clarify, pre-WWI English 1 1/2 oz. shells were black powder

1904-1914 W.J. Jeffrey & Co. catalogs (courtesy of Boyd Taylor Thompson) listed the Jeffery "Long Range" hammerless "Waterfowl" gun available in 3" chambers that "can be used with from 4-5 drams of black powder and 1 3/8 to 1 1/2 oz. of Shot".
The standard Pigeon load of 1 1/4 oz. 3 1/4 Drams Curtis & Harvey�s No. 4 T.S. (Black Powder) was about 8500 psi.
Live Bird loads with 1 1/4 oz. 3 1/2 Dr. Eq. Bulk Smokeless Powder would be about 11,750 psi



The "Magnum" English 12bores were contemporary with the U.S. "Long Range" guns and Western's Super-X boomers