We hear the term in proof and think that says it all. It does not. One of the 2” doubles on the upcoming Holts SealedBid auction tomorrow, has a barrel which is .006” thick I understand. The 2” guns were struck extremely thin to keep their weight down when made. Originally they were proofed at 2” but now I understand they are proofed at the same proof pressures as 2 1/2” guns. A much higher proof level. Lot number 5855C 2” non ejector FP Baker. Walls at .017 and .006. Still in proof otherwise could not be sold except for sleeving. Do not think “in proof” says it all.

So again proof is not a guarantee of being absolute safe to shoot. You still need to measure and know the wall thickness. They do not tell you where the wall thickness is down to .006, but to me it does not matter. For a reference I think your coke can is .0035-.0045”. .006 I expect you could dent with your thumbnail. If a dealer would never submit a gun for proof is it even a gun you ought to buy it and no dealer or smith would e er submit such a thin barrel for proof.

So when you read in the description that “wall below recommended thickness” you need to become very cautious. They are pointing out a potential major flaw and you need to understand it. Many of these guns end up on SealedBid because they are cripples or project guns needing work. In the main sale they list bore measurements for all the guns. They do not do so for sealed bid guns.

Are you sure it is .006? That sounds like a misprint. I wonder when the gun was proofed (proved) because at .006 it should be out of proof.

Ken

Proof is only determined by bore size,not wall thickness .
A barrel as thin as that quoted could be the result of a poorly excecuted dent removal in the past .

A Coke can is .005 thick.

As far as I am aware the British Proof houses do not measure wall thicknesses. They take the view that if the tube does not bulge, rivel or burst when fired with a Proof load it is strong enough.

A weakness of that approach is that whilst a barrel goes out of Proof is the bore is enlarged over 10 thou, it still appears to be in proof if under that bore size even if it is repeatedly and over enthusiastically struck down, polished and re-blacked no matter how close the external diameter is approaching the internal diameter.

Some European Proof Houses stamp the weight of the barrels at Proof, and I believe those barrels will go out of proof if they suffer a certain percentage loss in weight.

Proofed, proved or in this case poof. Yes I am sure of the measurement. It also is clearly stated in Holts description. The proof house does not measure wall thickness. As to how thick were the original barrels, nobody knows for certain, but I’ve been told they all started out about .020. I have a LeFever 20 which looks mint condition and it’s barrels are .020. It shows no sign of ever being reamed, honed or restruck. So thin barrels can be anywhere. Again I listed the auction item number 5855C. Look it up.

A gun is out of proof if a plug .010 larger than the plug used to determine bore diameter goes down 9” where the bore is measured. So a gun with a .720 bore is still in proof if a .730 plug will not go the full 9”. It might be .728 or .729 and if the plug won’t go it is still considered in proof. Also any alteration of chambers will put it out of proof. So if the barrels start out at .025 thickness and gets cleaned up to .008 to remove pits it still is in proof. But and this is a big, but the wall thickness may have gone from .025 down to .017. Thin but still in proof. You will see this commonly listed as “barrel below recommend thickness”. It is still in proof and legal to sell. Deciding if you want to shoot it requires you to measure it accurately and then make a judgement. But never assume just because a gun is in proof it is always safe.

Per Vic Venters' book "Gun Craft", quoting former proofmaster Roger Lees, who held that position when the 1954 Rules were adopted, referring to those new rules: "in general it may be said that under the new Rules of Proof no arm will receive a more severe proof than hitherto. Some such as the 12 bore 2 inch and 4 and 8 bore guns, will now receive a less severe proof than they received heretofore." I thought I recalled that the Brits went to a less severe proof for the 2" 12, as requested by makers of those guns, under the 1954 rules of proof. I think that continues to the present.

Confusion here, where 2" 12s are concerned, may stem from the fact that when the Spanish made their 2" 12s, they submitted them for 850 bar proof, just like standard 2 1/2" 12s. Which explains why Brit 2" 12s are typically quite a bit lighter than Spanish 2" 12s.

Well this is confusing. As Larry said, the data I have is that 50mm have the same pressure standards as 65 mm & 70mm

90 BAR is only 1,305 psi; 117 BAR proof is 1,697 psi
SAPL
https://www-boutique--sd--equipemen...r_tl=en&_x_tr_hl=en&_x_tr_pto=sc



but https://bobp.cip-bobp.org/en/tdcc_public?page=1&cartridge_type_id=7 doesn't show a 50mm standard??

I owned a 2” several years ago. The loads it used generated a lot more than 1,305psi. More along 8,400psi. One factory shell I could get were Lavale I think and they were really unpleasant to shoot. About as unpleasant as shooting a 3” 20. 2” 12 were struck light to really be a 20 gauge type feeling gun. You ended up with a 5 pound gun with IM chokes in both barrels. I tried a 15/16 load which patterned very poorly. My best load was a 7/8 ounce load and one Federal paper cutdown load which was 13/16 ounce.

I moved on from it because it did nothing a good 20 could not do much better and the 20 could handle a full ounce where the 2” 12 could not. Or at least mine patterned poorly with anything above 7/8 ounce. I was told one maker made just about all the 2” guns no matter what was engraved on them. For those who own and love them you don’t have to worry about my bidding against you for one. Enjoy them in peace.

An English gun that has passed proof, and maintains the original bore dimensions, but, is down to .006 on wall thickness at some point, has suffered some sort of poor gunsmithing, and, I think this is important, would certainly not pass proof today. Being in proof is just part of the puzzle, other facts and measurements will be required to know what level of ammunition, and, use will be acceptable. The use part is important as well, I owned a very old MacNaughton boxlock, the second gun produced by the firm with steel barrels, that I thought was going to be my daily shooter, clays, birds, Grouse, pheasant, woodcock, everything.

The gun had other ideas. Expensive ones.

Proof is no more than a snapshot of what things were in the past. Compromise is often part of the picture with an old gun. And a gun with .006 wall, is compromised.

Best,
Ted

I work in the pressure vessel industry, and I would substitute the word 'terrifying' for 'compromised.'

Six thou' is roughly two sheets of cheap photocopier paper thick.

To paraphrase Ronald Reagan, Trust but measure. Assume nothing until you know.

I recall reading (somewhere) that with some 12 ga. 2' doubles it was believed(speculated?) that barrels were proofed in the white and when finished by the gunmaker, the barrels' exteriors may have been further struck to reduce weight which would have left bore measurements intact. I'd verify the MWT as it does sound like a misprint. Two pieces of copy paper stacked together measure .007". Here's an article that discusses the 2" 12 ga. guns and it mentions wall thicknesses with one gun measuring .012".

https://shootingsportsman.com/short-shell-12-2-guns/
Gil

Jon, you're referring to Lyalvale shells. They are unpleasant, for sure. The late Bill Hanus was hawking them at one point. Sent me some to try out. Back then I often shot skeet with a lawyer friend who owned a really nice Lebeau Courally boxlock. I handed him a couple Lyalvales on Station 1: "Here you go, Bill . . . give these light British loads a try!" He only shot one of them and had some very unkind words for me.

I'll throw my thoughts and experiences in on this one.
1st Drews pressure data. The SAPL after 12/50 should alert us to something unique to this pressure. A click on the link provided Shows cartridges 12/50 with a note "FUN tir cartridges are a 12/50 caliber "gum-cudgel" type cartridge that can only be used in products from the SAPL Co. I translate gum-cudgel as Rubber Club. They look like non lethal defense products firing a rubber ball.
2nd GLS comment Pretty much all new production guns are finished "In the White" with some polishing afterwards.
3rd Ted S/Imperdix" comment are I'm sure the answer.
A wall thickness survey before and after the thin spot,particularly adjacent to but up against the ribs would most likely tell what the original thickness was.

I once sold a 1935 H&H 12-2" Dominion back to H&H New York.So as not to waste time doing the Wall Thickness song and dance I advised Guy D. The wall thickness is only .014" each Barrel. 9" back from the Muzzle. Without looking up from the gun he said "Don't worry that's the way we made them!
Hope some of this helps. It's a Sleever for sure, good lock finding suitable tubes.

This statement is not correct. If the bore of a gun is opened or honed to an inside diameter. 008" larger than its' original proof bore diameter, it will still be in proof, as stated. But the barrel wall thickness will not be reduced by .008". On average, the wall thickness wiil only be reduced by .004". In this example, the original wall thickness of .025" will not be .017" after reaming or honing, but more like .021". That's a significant difference.

I am curious about the location of the area in the barrels mentioned that have a .006" MWT. I agree with Ted and Fudd about them being both very compromised, and scary too. I don't want even 1000 psi of powder gasses abruptly escaping anywhere near my eyes or fingers. There are too many perfectly sound guns available to risk using one with barrels that are soup can thin.

Yes Keith you are right. But the point is being in proof means nothing as to being safe. Many here, think being in proof is good enough. The gun listed above is clearly in proof and has a wall thickness of .006. I doubt anyone here would be happy to find out their new purchase has walls that thick and I doubt anyone who sees what .006 looks like will shoot it. I doubt a .006 tomato stake would last long.

A gun passing proof with MWT of .006 does not make sense to me. Something doesn’t jive; there’s more to this story. I would think such a gun would be summarily rejected by the proof house regardless of whether it survived the proof loads. The authorities responsible wouldn’t be so hidebound as to pass a gun that was obviously unsafe, would they?

Hugh--Glad you chimed in! I remember looking at a 2" 12 in your shop and discussing the fact that barrel walls often left the maker on the thin side. And I think I recall discussing the lighter proof that was allowed on 2" 12's under the 1954 rules with you.

eeb, this gun did not just pass proof. I am sure it was proofed with barrels thicker than .006. Holt's has clearly stated the barrels now are .006 and that it is in fact still in proof and legal for them to sell. How is that possible? Proof does not include a wall thickness determination. The proof house does not measure wall thickness. They give you a yes or no answer to does this gun pass a proof load with out issues.

Perhaps it had a dent that was raised and struck before reblacking. I bet that it was a dent raised which is the root cause instead of honing to death. SO it might be a localized issue but where is the issue. Perhaps it has been reamed out to clean up pits down the bore, but the first 9" still have some metal left so it is still within .009 of what it was proofed. IF the original barrels were .014 and it has been honed until they are now .006 they could still be in proof. Just not anything I want to buy and certainly nothing I wish anyone here to use thinking being in proof means safe to fire. Measure everything and then decide what your level of risk you want to take. A .006" spot an inch from the muzzle might be a judgement call but not one just under your left hand. That is a accident waiting to happen.

IN PROOF MEANS NOTHING CERTAIN BEYOND LEGAL TO SELL. IT IS NOT A GUARANTEE OF SAFETY MANY ASSUME. END OF LARGE PRINT.