Does anyone have any idea what pressure levels a gun, which is reproofed to a black powder pressure load, might be? Gun in question was Black powder reproofed in 1931. I understand you could always request reproof to a Black powder proof, which was a lower proof pressure. Where this gun gets a bit tricky is the chamber lengths were 3 1/4" so I do not know what shell it was proofed at. Gun is in shipment so I can not get any photos to help. I suspect there was only one Black powder proof load used for all chamber lengths. I was hoping someone knew what "Black powder proof" was, like 6 drams powder, and then we could work out a general pressure level. I have a email in with the Birmingham Proof House as well so hoping they can help as well.

If you have a Dixie Gun Works catalog it might be in there. For some reason I seem to remember seeing that years ago in one of their catalogs. Wish I could be more specific

Not trying to complicate matters, but I understand that some guns were given long chambers to accommodate longer wad columns for live pigeon shooting to improve pattern but not to increase the load.

So 3 1/2” chambers may not equate to a heavy load.

Do you know what the gun weighs?

Applying the formula of at least 1lb. of gun for every oz. of shot should provide some guidance.

1896 Rules
The pressures were determined by lead crushers (LUP) so modern transducer numbers would be 10 - 14% higher



https://books.google.com/books?id=inQCAAAAYAAJ&pg=PA2&dq
Powders used for proof are given as T.P. (Tower Proof) “which shall be of strength equal to Waltham Abbey “R.F.G. 2” and of grain varying between Nos. 4 and 5, that known as Curtis and Harvey's “T.S.” (Treble Strong) No.2 [for Supplementary Nitro Proof with 4 1/2 Drams and 1 2/3 oz. “soft” No. 6 shot] and, that known as “Col. Hawkers Duck Gun Powder”, and the nitro-powder known as Cordite, or any other description of nitro-powder which may hereafter, from time to time, be adopted by His Majesty's War Dept.”

Curtis & Harvey “T.S.” (Treble Strong) No. 6 (84 grain = 3 Dr. Eq.) was coarse Black Powder somewhat similar (but not equivalent) to Fg.
“T.S.” was developed in 1871 for the .577/450 Boxer-Henry cartridge used in the Martini-Henry rifle. It was a precursor to “R.F.G.2” (Rifled Fine Grain 2) manufactured at the Royal Gunpowder Mills, Essex, adopted in 1873.
C&H, “T.S.” No. 4 (82 gr. = 3 Dr. Eq.) medium grain similar to FFg
C&H, “T.S.” No. 2 (72 gr. = 3 Dr. Eq.) fine grain similar to FFFg.

I don't have the Black Powder Rules after 1925, but suspect they were similar
The 2 1/2” & 2 5/8” 12g Definitive Proof remained 6 1/2 Drams BP with 1 2/3 oz. shot
The 2 3/4” 12g Definitive Proof was 7 1/2 Drams BP with 2 oz. shot.

So if it was proofed at 6 1/2 with 1 1/2 ounce shot or or 7 1/2 drams, with 2 ounces shot, we are looking at a proof load of at least 10,100 psi.? I figure a 3 1/4" gun might be proofed at the higher 2 3/4" load. 2 1/2" would be the lightest it was proofed at from the chart and I wan t to be on the lower, safe side. Using a 70% service load estimate give me a service load of 7,000.

C&H, “T.S.” No. 4 (82 gr. = 3 Dr. Eq.) medium grain similar to FFg "Service charge of 7790 1 1/4 shot 3 1/4 dram load", "5820 for 1 1/8 ounce, 3 dram load" is a commonly used charge. Taken from the chart above.

It will be interesting to see what the Birmingham Proof house says, if anything.

Assuming that the gun in question is 12G, Burrard 1st ed. 1932 Proof and Service Charge table gives for 3 1/4" (up to .740" in bore) - Definitive Proof 226 grains TSP ( =8 1/4 Drs ) to 2 3/16 oz shot. Service Charge 3 3/4 Drs to 1 1/2 oz.

Be aware that some of these 3 1/4" 12G guns may actually be nominal 10G although measuring as 11 or 11/1. Some will also be proofed for Nitro and up to 2 oz . A number of these guns will have been built to special order hence the variations in proof and service charges.

Thank you greener. That proof would be for Nitro?? Did Burrard mention a different Black Powder proof?

This chart is from “Proof Tests and Proof Marks: Practices of Manufacturers in the United States”, 1934 and only has the 3" charge.
Limits are based on the 1925 British Rules of Proof. Long tons are converted to PSI simply by X 2240, and the numbers were measured by LUP so require adding 10 - 14% for modern piezo transducer numbers.

3" same grains powder and shot

Burrard 1st Ed provides a table of Proof and Service Charges which includes 3 1/4" 12G as above noted, however the separate Table for All Sizes of British Cartridges does not include the 3 1/4" cartridge load.


Later editions eg 1960 does include the 3 1/4" loads - for 33grain, 43/1 1/2oz

36 " 46/1 1/2 oz

42 " 54/1 9/16 oz

BP - 4Drs/1 9/16 oz

Also includes Low Velocity loads for 36 grain smokeless nitro powder and Black Powder.

Guns chambered for thin brass cases were built as pigeon and wildfowl guns usually 2 3/4" upwards and probably even in standard game guns, so called "chamberless" guns. The 12/10 cartridge was manufactured for this class and I think that this type of gun was generally built to accomodate the heavier loads on the low velocity principle. Paper case guns were also produced in 3 1/4" length.

I have seen a 3 1/4" chambered gun stamped with Nitro Proof for 1 3/4 oz , original, a nominal 12 although measuring in 10 gauge classification, and apparently a paper case chambered gun. So far I have not found any Proof House data for a 1 3/4 oz Nitro load. The gunmakers who specialised in construction of this class of shotgun ( Ford, Jeffries, Greener...) to customer order would have specified the load particulars to the Proof House .