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

I would like to see the video of them doing that.

Here you go. Give it a whirl.

https://www.gunsinternational.com/g...kal-izh-18m-m-12-ga.cfm?gun_id=103678922

I think one of the Brits told us this. I believe the information was discovered quite by accident.

The beautiful truth here, is, if the gun doesn’t survive the test, no one will care.

Best,
Ted

Builder: I resonate with 12boreman's perspective here.

Like him, I've been shooting Damascus guns for some time now (close to 30-years as well). For me it was a voyage of discovery (lots of reading and metallurgical inquiry) and only after I had done my own "due diligence" did I make that decision.

My own science background is not to the "do all, end all" level that I'd like it to be, but I made a living with it for the better part of 40-years and have never killed or maimed anyone yet.

From what I've read & seen here, I'd be more concerned about the wood on this gun than the tubes.

Some entertaining (and alarming) anecdotes at the bottom here regarding the challenge of bursting pattern welded barrels
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit?tab=t.0

What doesn't burst one barrel of course may have no correlation to what will burst your (unexamined) barrel

IMHO 2nd hand gun barrels DO need to be measured. I've posted this before (and it's not mine). Perazzi MX2000 barrels bought 2nd hand reported by the seller to have been backbored - it was honed to .012".



And IMHO a vintage gun (esp. from the corrosive primer era prior to c. 1930) with 'mirror bores' strongly suggests previous honing
https://www.doublegunshop.com/forum...p;Board=1&main=50086&type=thread



The vast majority of vintage bores look like this, or worse

I am happy to see renewed interest in this post. The information is valuable to all that read it. A problem with picking up in the middle of a thread is you miss the original topic although thankfully it has not gone in a crazy direction nor a political rant. The original post is about safety when shooting Damascus barrels or actually any barrel. Wall thickness is especially important in the first half of the barrel when it comes to safety. Different distances from the breech need certain thicknesses of the barrel wall. Generally the closer to the breech the thicker the barrel walls should be. Assuming there are no defects in the barrel, there are general rules of thumb even though nobody can guarantee, nor should they, the thickness required at various distances from the breech. Although it is important to know that very thin barrel walls, usually found in the last 10 or so inches, are subject to physical damage such as denting but my barrels do not have that problem. My first post made it clear that I know how to measure wall thickness throughout the length of the barrel. The numbers I was measuring and listed in the first post felt a bit thin to me and I was hoping to get responses to that and I did and I thank those who responded. It helped me decide what I would do and that was to shoot it with low pressure loads that I make using previous tested loads.

I think it was Rabbit, G-d rest his soul, from days gone by who advised us not to go too low on the pressure. Advertised pressure is chamber pressure. If I recall, his opinion was that if you went too low in chamber pressure, the pressure down the barrel would not dissipate as much since you needed a certain amount of energy to propel your load down the barrel at the prescribed speed. Please, I did not say the pressure increases down the barrel. Maybe some of you old timers here remember this and can explain it better than I can.

Found this thread from 2013 which is not quite the topic
https://doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=334038&page=1

Miller and Jack made the point that lower chamber pressures (for equivalent weight and fps) were attained using slower burning powders ie Red Dot to Green Dot to Blue Dot. But by doing so the pressure would be slightly higher further down the barrel.

Obviously computer generated illustration from an old Alliant resource



DuPont Oval was a progressive-burning "controlled combustion" smokeless shotgun powder developed for the Western Super-X loads.
This is from “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics” by Wallace H Coxe; E.I. du Pont de Nemours & Co., 1927, a DuPont Oval Pamphlet, p.20.
Charge was 3 Dr. Eq. and 1 1/4 oz.
Pressure is expressed in Long Tons. sq/ inch but it appears that PSI X 2240 was used to calculate those values (+ 10-14% for modern transducer numbers)

Ballistite maximum pressure at 1” was 4.9 Long Tons = 10,976 psi
Schultze at 1 3/4” was 4.5 Long Tons = 10,080 psi
DuPont Bulk at 1 2/3” was 4.1 Long Tons = 9,184 psi
FFFg at 1 1/2” was 3.8 Long Tons = 8,512 psi
DuPont Oval at 2” was 3.5 Long Tons = 7,840 psi
BUT the pressure generated by Oval at 4 - 6" was higher than the other powders.
At 4 1/2" Oval was about 3 Long Tons = 6729 psi and the others were about 2.5 Tons = 5600 psi (+ 10 - 14%)
I'm not a ballistic or mechanical engineer to know if that matters.

I miss Jack. Gilbert, too.

Others, of course.

Best,
Ted.

Milt, very nice gun. Chain Damascus was usually put on higher graded guns, although I have a F grade L.C. Smith hammergun that has Chain Damascus barrels. I believe someone made a mistake when the barrels were first struck in the white and put into the wrong bin. Since it was already struck and serial numbered to the gun, it was sent sent this way. I doubt that it was special orfered, as the barrels probably cost more than the gun.

In my opinion I believe those reading are acceptable and safe to shoot with your low pressure loads. If you go and look at Doctor Drew's site and look at the pressure readings with different powders it shows that like stated the most important readings are at 9" from the breech. At 15" presssure is dropping and at 20" and up it is less than half.
I always thought it interesting that in some skeet and trap guns, near the muzzle there were holes drilled in the barrels to let off what ever. Maye someone could explain that.

Have fun shooting it, but I still like your 20 ga. L.C. Smith with the 32" barrels. You shoot that very well.

Thank you for your response David. The only thing nicer than hearing from you is seeing you. It is funny to me that I shoot certain guns better than others like my 20g. Smith and my 16g. Fox (and others). It is not the fit since I make them all fit me. Maybe the balance works for me. I don't know. Right now the Francotte is apart being worked on but I did shoot it and it has not blown up yet.

Best,
Milt

[quote=David Williamson
I always thought it interesting that in some skeet and trap guns, near the muzzle there were holes drilled in the barrels to let off whatever. Maye someone could explain that. [/quote]

Porting a barrel is intended to reduce muzzle flip and sometimes recoil. In addition to shotguns it is often done on pistols and sometimes rifles intended for competition or other situations where rapid fire is expected.

For a SxS or more likely an O/U or semi-auto it is intended to reduce the muzzle flip to help pick up a second bird, real or clay.

I dumped the into Microsoft Copilot and got the below answer, which is probably more information than anyone really wanted:

Porting does reduce muzzle flip, but the way it works—and the situations where it actually helps—are often misunderstood. You’re already on the right track, so let me build on what you wrote and add the deeper mechanical context that shotgun and competition‑gun people usually care about.

🎯 The core physics: why porting reduces muzzle rise
When a gun fires, the muzzle wants to rise because the bore axis is above the shooter’s hands. Gas exits the muzzle and pushes the barrel upward like a lever.

Porting vents some of that gas upward, creating a small downward counterforce.
More ports → more gas redirected → more counterforce
Larger ports → same idea, but at the cost of noise and blast
Placement matters: ports near the muzzle have the most effect

This is why porting is most noticeable on:
Short‑barreled pistols
Lightweight barrels
Guns with high bore axis
Guns fired rapidly

Shotguns fit that last category perfectly.

🦆 Why porting is used on O/U, SxS, and semi‑auto shotguns
You nailed the main reason: faster second‑shot acquisition.

For clays (skeet, trap, sporting clays)
Porting helps the shooter:
Keep the barrel flatter during the first shot
Track the second bird more quickly
Maintain a smoother swing without the barrel jumping off line

On an O/U, the top barrel usually gets more muzzle rise, so many porting patterns bias the top barrel.

For hunting (upland, waterfowl)
It’s less common, but some hunters like porting because:
It keeps the sight picture flatter
It helps with quick follow‑up shots on flushing birds

But many hunters avoid porting because:
It increases noise dramatically
It throws gas and debris sideways, unpleasant for partners or dogs
It adds cost without huge benefit for single‑shot situations

🔫 On pistols and rifles
Porting is used for the same reason—control during rapid fire—but the effect varies by platform.

Pistols
Porting is extremely effective on:
Compensated race guns (Open division)
Short, snappy carry pistols
High‑pressure calibers (9mm major, .357 SIG, .40 S&W)
Gas volume is high, barrel length is short, and muzzle rise is significant—perfect conditions for porting.

Rifles
Porting is less common because:
Rifles already have low muzzle rise
Gas pressure at the muzzle is lower (especially with long barrels)
Muzzle brakes are far more effective than porting

You mainly see porting on:
Pistol‑caliber carbines
Short‑barreled rifles
Competition guns where recoil management is everything

📉 What porting doesn’t do well
A few myths worth clearing up:

Porting barely reduces recoil
It changes how recoil feels (flatter, less jumpy), but total rearward force is almost unchanged.

Porting doesn’t improve patterning
Any claim that it “tightens patterns” is marketing fluff.

Porting doesn’t help slow, deliberate shooting
Its benefits only show up when you’re firing quickly.

🧩 The shotgun‑specific nuance
Shotguns have long barrels and relatively low gas pressure at the muzzle compared to pistols. That means:

Porting’s effect is real but modest

It’s most noticeable on lightweight sporting guns

It’s least noticeable on heavy trap guns or gas‑operated semis (where the action already reduces muzzle rise)

This is why some shooters swear by porting and others say it’s pointless—it depends heavily on the gun, the shooter, and the discipline.