doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com British proof questions.

What was the black powder proof load for a 20 gauge? Did it change from the same 20 gauge as a muzzle loader? Was it in grains of black powder or drams? Thanks for any knowledgeable answer.

I was at a large muzzle loader shoot this weekend and one builder explained what load he proofed his guns at. It was scary. Much greater than a double load of powder. Got me wondering what proof load my 20 bore suffered when new.

1896 Rules of Proof
https://books.google.com/books?id=inQCAAAAYAAJ&pg=PA296
12,920 psi + 10-14%

Muzzle loaders would have been proofed under the pre 1855-1868 proof laws I expect for the most part. Some would have been done under 1856-1868 time period. Don�t expect many were made after cartridge breech loaders came into fashion and by 1868 they had to by taking over almost all new construction.

Basic black powder proof time frames.
1637- 1855 London black powder.
1817-1855 Birmingham black powder
1856-1868 London and Birmingham black powder
1868-1925 London and Birmingham black powder.

So I guess what I need to find is the black proof levels for a 20 gauge muzzle loader before 1856 and compare it to the cartridge proofs for 20 gauges after 1856 or 1868 if I can�t find that. I�ve sent an email to the Birmingham Proof house hoping they can tell me. Also I asked what reproof levels they would subject a 20 gauge muzzle loader gun to today, if submitted for reproof.

I may be wrong but I don't think there will be any difference between the ML proof charge and the BL. The laws of proof are governed by CIP and they would view all guns in the same way from a testing pov.
Whether testing a 1850 London made pinfire or a 2019 Turkish 5 shot semi-auto, the test is the same (other than variation for chamber length, steel pressures etc) and I don't see why they should view a ML any different.
Only variation I could imagine would be black powder v nitro but I think the pressures would be similar.
The test is defined by chamber length, standard/superior pressure and nitro/black.
Here you have the challenge in reproofing old guns: the test is designed to protect the simplistic, ignorant user not the well-informed collector. I and my colleagues who 'specialise' in getting guns back into use after a century of collecting dust and rust deal with this on a weekly or monthly basis and the unpredictability of the proof house in their decisions on fail or pass drives us round the bend! To be fair, the decisions they have to make on pass/fail are often very border line and we are sometimes blessed with a pass that in all honesty might be considered a fail. The test results' can sometimes be surprisingly nuanced and I am often grateful that a degree of discretion still remains.

Jon;
I am going to have to do a bit of digging but I am quite certain I have a proof chart but don't recall which date, that gives the actual Black Powder charge used for the various gauges & lengths of shells. In the muzzleloaders as well as early breechloaders sans choke the proof was done using a close fitting round ball rather than a shot load. The BP charges were extremely heavy though. I do have an I Hollis 12ga MLer which bears the combination mark that both provisional & final proof were conducted as one. The heavier provisional charge was used at final proof. Best as I have been able to determine this mark was not used prior to I believe it was 1887. This gun was thus obsolete when it was built.

Page 20 of the published UK book: "RULES OF PROOF 1954" contains the following chart titled: "APPENDIX II, SCALE I, FOR THE PROOF OF BARRELS AND ARMS OF THE FIRST CLASS"

From this chart provisional black powder proof of 20 gauge 2 1/2 and 2 3/4 inch cartridges using TP black powder ( TP = Tower Proof powder) was 205 grains with 7/8 oz. number 6 shot.

From this same chart black powder Definitive Proof of 20 gauge 2 1/2 inch cartridge proof was 136 grains of TSP (Tower Special Proof black powder) and 1 5/16 oz. number 6 shot. Additionally the black powder Definitive Proof load for 20 gauge 2 3/4 inch cartridge was 157 grains of TSP with 1 1/2 oz. number 6 shot.

The Definitive Proof loadings of Smokeless Powder is not listed with the chart reading: YET TO BE DETERMINED.

Those loads should quickly weed out the weak from the strong.

I suspect that these black powder proof loads had been used for many previous decades.

Yes, "2-piper" they are extremely heavy to my mind also.

Thank you bushveld. 136 gr. = 5 Drams so the 2 1/2" definitive proof was about the same (1 1/4 oz. in 1896) as the 1896 Rules.

W W Greener shows the 1904 proof charges in his 9th Edition of The Gun.
Black powder proof for 20 gauge was
Provisional = 205 grains TSP (7� drams) with 7/8oz shot (383 grains
Definitive = 136 grains TSP (5 drams) with 1 3/16 oz shot (520 grains)
Service = 68 grains (2� drams) with 383 grains shot (7/8oz)

Supplemental proof for guns to be used with Smokeless Powder
95 grains (3� drams) TS2 with 574 grains shot (1 5/16 oz)
Service only lists 7/8 oz of shot, no powder charge stated so assumed to be same 2� dram equivalent.

Almost identical to the 1954 rules half a century later. The only difference I note is the 1 3/16 oz shot charge in definitive proof in 1904 versus the 1 5/16 oz in 1954.

No chamber length is given in these 1904 rules so apparently the same for all lengths.

WWG - 1878 Rules
Class 4 breechloaders
Double the service charge of powder : One and one third x the service charge of No.6 soft lead shot.

So a 200% powder charge. Don�t know if I�d ever subject my 200 year old muzzle loader to that standard. I�d rather hang it over the fireplace. I did shoot it a couple dozen times without incident this weekend. But I don�t see the value of proof in this case. I did a 50% overload test, but not to this level.

Proof Laws to protect a buyer are fine and great for the seller, when a gun passes. Gives them a bit of legal cover and the seller knows his �new� gun has a decent level of safety in use. But I remember a 20 gauge Clark hammer gun which passed reproof and failed within a box of shells. But I�m sure a gun which fails, even when not a catastrophic failure, saddens everybody. Old guns deserve to be shot, if they are safe.