doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Wall thickness opinion

I just purchased a beautiful Francotte with very fine checkering, lots of engraving and chain link pattern on the Damascus barrels. I would love to shoot it but I am not sure if the wall thickness is safe. I have the vertical wall thickness gauge from Galazan most of you are familiar with. It has the three vertical rods for different gauges. I do know how to use it and I took measurements every three or five inches which I will list here. I would appreciate comments from knowledgeable members to guide me. I reload lower pressure 12 gauge loads. The bores measure .733 and .736 and the metric proofs convert to .728. I realize nobody can tell me if it is safe to shoot however I would like to hear from you based solely on the numbers below. Thanks all!

Measurements are from the breech:
Right barrel Left Barrel
3" .115 .097
6" .067 .064
9" .048 .046
12" .043 .034
15" .035 .023
20" .032 .022

It is marked 2 3/4" chambers and the rest of the measurements come in as safe in the areas I did not list.

Looks like a very safe to shoot gun based on those measurements. .

I'd shoot it.

Any pits? Share some pics, sounds like a beauty. RST says their 2.5” loads are 7500psi or less according to last phone call I made to them.

How long are the barrels?
.022 is awfully thin if that spot is where the pressure spike is going to be (usually around 9” from the muzzle).
I suppose it could be safe, until it’s not. Being that thin, as far down the tubes as your showing, is going to make dent removal or repair sketchy if you happen to damage the barrel. Especially when it comes to soft damascus barrels. Just food for thought.
Theres a very good reason that barrel guys and knowledgeable gunsmiths in general don’t recommend a MWT below .025.

Never seen a bulge or split 9 inches from the muzzle unless full of mud or snow(your probably screwed if you do that with any gun anyway!). I believe Churchill cut that spot on one of his with a razor to prove little pressure out there. Always good to have a gunmaker go over your gun and advise.

9” from the muzzle is exactly where barrel specialist measure for MWT. They measure there, at that specific distance from the muzzle for a reason. It’s a crucial area. What kind of barrel work do you do?

It is late here in NJ and I am beat. The barrels are 30". Sorry to have missed a very important point.

At 9" from the BREECH it is .048 and .046 for the other barrel. At 12" one barrel gets pretty thin and my hand will be there I think but half way at 15" it gets real thin at .023 and I have never measured but my hand has to be pretty close. The pressure is probably way down at that point I think. The bore is very smooth but I am sure it has been honed. I have inspected as best I can and the barrel walls look solid. The left bore is .736 meaning it probably has been honed .008". Maybe whoever recolored the Damascus barrels took too much off the outside in that area leaving .023 thickness at 15" from the breech. I am hoping to hear otherwise but right now I am feeling it is risky. After 20" from the breech, meaning the last 10" to the muzzle are at least .030 so that is no concern.

I hope my ramblings make sense.

I shoot several Damascus barreled guns at least every 3rd weekend but depend on gunmakers or Dean at skeets to check all my barrels. Again always wise to have gunmaker not gunsmitts go through your guns.Not trying to dispute you LeFusil .
https://www.doublegunshop.com/forum...Words=Tensile&Search=true#Post671032
https://www.doublegunshop.com/forum...=Destructive+&Search=true#Post593281

General thought is that .025 is reasonable, .020 is where you start to take notice and below .020 proceed with caution. I shoot guns with .020 barrels. Where it is thin is as important and how thin it is. 20" from the breech is not a big worry for me. I do use "sane" loads. 5,000 to 7,000 loads will do everything I need. I shoot a Pape 20 bore with .016" & .020" walls, but that is at 26 & 27" from the breech, on a set of 30" barrels. In that gun, I have shot several thousand 7,200 psi loads. I would not shoot factory shells because I have no clue what pressure they might be. Reload and stay safe. I am more worried about recoil and stock damage than barrel wall thickness and pressure. Keep the pressure moderate and shot charge light and you will do fine.

Dustin: could you please explain the pressure spike 9" from the muzzle?

Turn-of-the-century powder pressure-distance curves



c. 1930 powders and loads



Modern powders



I believe gun sellers report MWT at 9" from the muzzle because that is typically where the barrels are thinnest ie. about 20" from the breech and before the start of choke constriction. And IMHO that is not an adequate assessment.

just to be clear, I believe the pressure peak is 9" from breech, not muzzle

9” from the breech is where the proof house measures peak pressure in France.

.022 wall thickness gets my attention, not in a good way, in any older gun, especially if it was not proofed at that dimension. The .022 reading is out there, at 20” from the breech, the pressure is dropping at that point. I wouldn’t attempt to use the promotional loads on sale at Wally World, but, with decent low pressure stuff, it sounds like it would be fine.

Show us some pictures, Milt.

Best,
Ted

Builder: I do not read where you have said whether the gun barrels are currently "in Proof" or not---are they?

Stephen Howell

Stephen, I am not sure if I fully understand the Belgian proofmarks nor did I spend much time yet on researching. There are a lot of marks to deal with on the flats and on the barrels. Some, I have no idea what they are. My initial concern was simply measure wall thickness for safety and go from there. I just got the gun two days ago in the evening. My guess is all the barrel work was done in the USA.

I will take pictures as soon as I can and post them here. I think members might find it interesting.

Drew,
I don't know if you said what you said as a "gotcha" moment or not, but where did I say in my post that there is a pressure spike 9" from the muzzles? Where did I mention pressures at all?? I know you fancy yourself as a barrel specialist or "hobbyist" and you do manage to post oodles of tasty info here on the subject (a lot of which I have looked at, reviewed, discussed and learned from over the years), but have you actually done any type of barrel work? Do you know how barrels are struck down and shaped to accentuate the beautiful lines that most of love about a SxS shotgun? If you do, then you already have an idea that as the barrels are struck down to the proper profile, they are inherently getting thinner as we get to the muzzles.

The 9" from the muzzle being a crucial area for measurement is because when SxS barrels are struck down, prior to finishing, the sharpest taper and thinnest area where there is still significant pressure in the barrel meet up is usually going to be in that very spot. When you get down to the .020 MWT in that area, that is getting extremely close to not being a reliable amount of steel left to ensure that that area is going to hold together. It’s not definitive, it's an estimation. Now let’s talk about repairs; if that area of the barrels is now .020 after a dent or crease has been removed, that .020 area of steel might be somewhat fatigued. Think of a piece of plastic that is continuously bent, it starts to form that fatigue line in the material and we all know that it’s weaker and about to break. While metal isn't plastic, metal behaves in much of the same way. Figure in Damascus steel, high or low quality doesn't matter, and now your dealing with areas that have been welded that might already be somewhat weaker just due to the way it was constructed. I shoot damascus guns too, I've read all of the Bell articles, I'm not saying damascus is a death trap, but I wouldn't be shooting one with a MWT below .025. That's just me.

We've all seen old hammer guns with muzzles that are razor thin. I suppose one could say "I shoot a gun with .010 wall thickness and I've never had a problem". It really does depend on the location, how many times has the metal been fatigued prior to that thin area getting to its current MWT, what type of material is the barrel made from, what type of ammunition is going to be used, and lastly, what are you intending to do with the gun.....Hunt it? Strictly use it at the range? Safe queen?
If you're going to hunt the gun, you have to think about damage that might possibly occur while your doing that...if you happen to dent the barrels and the damage occurs at an area of .020 MWT, that's going to be a problem. If you're occasionally shooting the gun at some clay targets using appropriate ammo, then you might be ok... until your not.
When it comes to resale, more discerning buyers will simply pass...aka, your gun with .020 MWT becomes very difficult to sell.

If the gun has passed proof with thin walls, all that's saying is it didn't give way during that test, but who knows what would've happened if they fired another proof pill (?).

I simply asked a question Dustin. I've never claimed to work on barrels, in any manner. Research does however provide information, with which we can make decisions.
And this is what you said
".022 is awfully thin if that spot is where the pressure spike is going to be (usually around 9” from the muzzle)."

Do you understand my confusion?

I have no idea why but I find when I see muzzle and breech I have to think a bit to remember which is which. When quickly typing, it is real easy to use the wrong word--at least for me. Front and back would be a lot easier. The bullet comes out the front of the gun. Enough said.

Ya I do. I misspoke. Sorry about that. Did the rest of my post make sense?

Great discussion - interesting and useful.

[b][/b]
belgian proofs feature a reasonably useable metric - the weight of the barrel set when it underwent proofing. it's usually very visible and easily readable - as an example - 1 k 572 - which is 1.572 kilograms.

one of the handy dandy conversion functions indicates that is 3.46566676 pounds...round that off to 3.466 pounds. a barrel set is considered to be out of proof when more than 3% of the proofed weight is absent.

another handy dandy conversion function indicates that 97% of 3.466 is 3.362. so, if the present weight of the complete barrel set is below 3.362 pounds, by belgian rules those barrels are out of proof.

the problems of this system are quickly understood - they measure the set, rather than individual tubes, they do not provide allowance for opening chokes or extending chambers (either of which will reduce the weight), nor for shortening the barrels....and i have always wondered about the removal of a front sling swivel, quite common on belgian guns.

just a variation on the old rule - you pays your money and takes your chance...

A very interesting Damascus barrel in chain link pattern, and a very crude, talentless and uninspired engraving, that draws the whole gun down. Sadly.

Carcano

I guess I'm not sophisticated enough. I like that gun a lot. And fwiw, I regularly shoot a few guns with wall thickness in the low 20s and one that has a small area near the muzzle that measures 19 thou. All with low pressure ammo that I have loaded and I've sent the loads out for pressure testing.

thanks for providing good photos, on their basis, i'll start over;

the gun was not proofed for smokeless powers, the rule establishing the marking of barrel weights came into force on 6 june 1892, and at the same time chamber markings were required - shown as a fraction with chamber length over chamber diameter: example given is 70/20,6 (but with the 70 atop the 20,6 - that would be read as 70mm chambers over 20,6mm diameter just forward of the rim). so the gun was proofed no later than early june 1892, and i believe with standard (short) belgian chambers.

the 2 3/4 (inch) markings over the bore and choke measurements, i do not believe to be original to the gun - likely professionally applied when rechambered, but not done by francotte or the liege proofhouse. original bores were - 18.5mm, and both chokes were 17.7mm - .728 and .697 = 31 thou chokes.

not having supplied the serial number range it would be worthwhile to go to the bottom of each page here on DGSBBS - click on "other useful information" and then click on "high grade shotguns dates of production". the second line starts with francotte and goes back to 1887, that should give additional information to confirm or reject the information given here.

best regards

Tough to date definitively with the proof marks.
Obviously made for the U.S. market with the 2 3/4" and 'Francotte's Choke Bore'. I've seen the 2 3/4" mark on guns imported by William Reed, VL&D & others
Nice chain damascus likely by the highly regarding Delcour-Dupont (DD) which became Canons Delcour in 1921
Non Pour Balle is usually pre-1897 but on the barrel rather than the flats. CHOKE just means muzzle constriction > .08"
It is not Nitro proved which is not uncommon on guns for export to the U.S. as it entailed an additional cost and was not required until 1924
The muzzle constriction over bore was used 1910 - 1921 (if there is no lettre annale) but I've seen earlier guns with the mark.
17.6 mm was the bore at the time of 1st provisional proof and at 3rd finished proof the bore was 18.5 = .728" and muzzle 17.7 = .697"
The Francotte models changed in 1910 and I suspect that's about when it was imported.
If a lower grade 1910 would be 3069something and if medium 709something
The models are here
https://www.shotgunworld.com/threads/abercrombie-fitch-von-lengerke-detmold-and-francotte.393236/
Bob Beach would know the grade and he does occasionally look in on the Forum
Cornell Pubs has a 1908 VL&D catalog repro (available as a PDF) but I don't know if all the grades are shown
https://cornellpubs.com/product/1150/

2 3/4 looks original based on other AF guns same era

Bob and I are friends and shoot together. He lives about a half hour from me. I emailed him the serial number but I doubt it went through the companies he has records for. He has not gotten back to me yet.

This is an ejector gun and has a gold band between the short rib and the main rib. The chart below says it is medium quality and 1896. I love the engraving on the balls and the bottom including the trigger guard and lower tang. The side engraving is similar to almost all the Francotte guns I have seen.

I stand corrected. The barrels have not been struck after manufacture. All the barrel engraving is intact and sharp and so are the letters and numbers. There is a gold band between the short rib and the main rib. The gun is an ejector gun.

It does say "choke" on the barrels about 1-2" in front of the flats. It also has the serial number there too.

I am curious of the significance of the 2 teeny tiny AF with a crown over each on each side of the flats toward the front. You can see it on the first four pictures.

Bob just contacted me. They have no record of this gun but he is visiting the site right now.

Very pretty Damascus, Milt.

Thank you Stan!

Found a couple of interesting Francotte guns

SN 32145 c. 1898. Siemens-Martin barrels with 2 5/8" chambers and not Nitro proved



VL&D marked 10g SN 33751 c. 1900. 4 Iron Damas Crolle with 2 7/8" chambers



Both have 2 sets of muzzle over bore dimensions.
Belgian First Obligatory Proof for “Double-Barreled Breech-Loading Sporting Guns” was for breech plugged tubes. The barrels were marked with the bore (often overstamped at 3rd Proof) and received the script EL provisional proof mark.
Second Obligatory Proof was for joined barrels, fine bored and finished; likely the first set of dimensions
Third Obligatory Proof was for finished barrels attached to finished action and likely the second dimensions typically with a slightly larger bore

Drew;

Who do you think stamped the barrels 2 5/8? Was it stamped by the proofing authorities or was it stamped after proof by others?

KInd regards;
Stephen Howell

Very likely the maker. I've only seen chamber length in 'American' on guns obviously intended for export to U.S. dealers, and the proof house would have used mm.
As you know 'choke' in English is 'choke de canon de fusil' in French. An 'express' rifle is 'fusil express'.

Drew;

That is my take on the stamping in "American" chamber length in inches as well. It is counter to logic that in a country where the metric measuring system is the standard that the proof "house" would stamp anything in inches.