Proofing a barrell

[Lutes]

I seen talk on here about proofing a gun barrel after it is put together. My question is what would considered a proper load and procedure for a 12 gauge shotgun barrel?

[Dphariss]

Greener shows 437 grains of powder and 535 gr slug for definitive proof of arms of the first class and the same charge for Provisional proof of the  second class. Second class definitive proof is 219 gr.  350 gr with the same bullet for Definitive proof of the third class. This from "The Gun and its Development" 1896 edition.
I have no idea what the 1st, 2nd and 3rd classes are.
Dan

[James Wilson Everett]

Guys,

Wow! Greener used really serious proof charges, for sure!  I proof my barrels at double the expected service charge of powder with a single patched ball.  In a 12 bore this would be about 200 grains FFg with a tight patched ball for the proof, about 90 grains FFg and 1-1/4 oz shot for the service charge.  The service charge uses the same volume powder and shot so only one measure is needed.  These are barrels made by me.

Jim

[Dphariss]

Guys,

Wow! Greener used really serious proof charges, for sure!  I proof my barrels at double the expected service charge of powder with a single patched ball.  In a 12 bore this would be about 200 grains FFg with a tight patched ball for the proof, about 90 grains FFg and 1-1/4 oz shot for the service charge.  The service charge uses the same volume powder and shot so only one measure is needed.  These are barrels made by me.

Jim

These are from the proof house tables. Individual makers have not done their own proof in England for centuries.
Given the bore sizes these are not exceptional. You must remember that the British did not want guns blowing off HRH's hands or face.
Dan

[gunmaker]

Back of dixie catalog gives British proof loads by gauge.

[Jerry V Lape]

Under the English proof laws of 1855 a single barreled birding or fowling piece for the firing of small shot were to be proofed as a 3rd class gun.  The definitive proof with a finished barrel and gun was to be loaded:     12ga with a bore diam of .729" used a ball of .709" diameter weighing 535grains and a black powder charge of 350 grains.  A double barreled shotgun was the 4th class and it's load for definitive proof was the same ball but the charge was reduced to 219grains of powder.  But these load did not specify patch or wadding to be used but it is probably reasonable to assume an over powder card under the bullet. 

The powder was Tower Proof Powder which was probably equivalent to GOEX FFg.  This is where we disconnect on the British Proof loads as there is no conversion tables between their powders and ours.  Currently they are using TS 2 which is available in England but again what the equivalent powder may be for us is an unknown.  If you come across Provisional Proof loads remember these are for barrels in their raw form, without final reaming, rifling, breaching, dovetail cuts for lugs and sights nor the final exterior contour.  They are much heavier and in my opinion not appropriate for proofing our finished rifles and could very well do stock damage if mounted. 

The real problem with proofing on our own is we don't have the measuring tools the proof houses use to detect any permanent enlargement of the barrel caused by a proof firing.  Such enlargement indicates the metal has exceeded it's elastic limits and therefore was not suitable for use.  They measure the barrel in multiple points especially in the most vulnerable area where the highest pressures occur around the breech.  Just because the proof didn't blow up the barrel doesn't mean the barrel is safe without being able to determine whether the elastic limits have been exceeded.  These measurements are in 10,000ths of an inch which is difficult with just a micrometer.   

 

[Dphariss]

If someone cannot tell a barrel has been enlarged they probably need to take up another hobby.
DOVETAILS in rifle barrels cause deformation of the bore, for example, that can be felt with a tight patch on a short  bearing surface jag.

AND its it very unlikely that a modern BARREL STEEL of a normal wall thickness that has no flaw will be damaged or stressed by any BP load that is driving a projectile. BP simply lacks the ability to make the pressure necessary unless the powder is fired in a "closed bomb" test. A gun barrel is not sealed to contain all the pressure it will possibly generate.
Also if  the elongated projectile is pure lead it will expand under acceleration to fill the bore probably before it even moves. So there is no significant gas leakage. The front portion of the powder charge actually serves as a wad that prevents blowby before the bullet expands. This is how the modern ML conical/cylindrical bullet works  to seal the bore and it is how cylindrical bullets worked in what were often significantly oversized bores in the original BPCRs or in choked bores in the case of many original slug guns.

Dan

[Daryl]

That is the way I "see" the proofing situation, Dan.

[Ezra]

Greener shows 437 grains of powder and 535 gr slug for definitive proof of arms of the first class

Umm, yeah, that should be suffcient...   Long lanyard anyone?

Ez

[Habu]

Greener shows 437 grains of powder and 535 gr slug for definitive proof of arms of the first class

Umm, yeah, that should be suffcient...   Long lanyard anyone?

Ez

Fuze.  And a little brother who will FOLLOW INSTRUCTIONS AND MOVE BACK TO COVER after lighting said fuze. 

Geez, it has been 30 years: you'd think he'd stop reminding me of that eventually . . .

[PPatch]

Lutes;

If I were you I would go with Master Everett's advice - Proof with a patched round ball at twice the powder charge you expect to regularly use.

Welcome to the forum sir.

dave

[Lutes]

Ppatch thanks for the welcome. Yea that is along the line of what I was thinking.

[Dphariss]

Ppatch thanks for the welcome. Yea that is along the line of what I was thinking.

If the firearm will ever find its way into someone  else's ownership or is used around the public its best to use a proof load that provides pressure similar to the proof house loads I listed.  I even video tape the shot. If the barrel ever fails or if a breech or vent comes adrift and someone is injured you better have some form of proof that the barrel was tested  and use a proof load that has some official backing. I do not know what the current proof rules are in England now but I doubt the BP proof has changed much.

Dan

[Daryl]

My Green River Rifle Works 1 1/8" across the flats .69 barrel was proofed in 1989, I think the year was. I'd accidently loaded a double powder charge while chronographing loads at the range above the jail where I worked. Since the normal charge was 165gr. 2f, the proof charge was 330gr., with a single 480gr. ball. Although the recoil lifted me up off the seat I was perched on, the velocity recorded at 1,770fps was only 220fps higher than what my normal charge provided for that load. Since that time, this barrel has seen a least 2,000 shots fired with the normal 165gr. load, in total satisfaction.