Help - Wall Thickness at the Muzzle ?

[jay shachter]

Hey Guys,

Regarding barrel wall thickness, I have measured literally thousands of them. If you are using 25 thou as your minimum, you will be retiring most of your 20ga. Parkers and "O" frame 16ga. Parkers, as well as many of your other fine lightweight doubles. Most light weight Parker 16's and 20's range between 20 and 25 thou as their minimum, usually 6-12"
back from the muzzle. I am talking factory original, unmolested, original blue and factory bore diameter barrels. I have measured a half dozen Parker ORIGINAL barrels that got down to 18 thou in the same areas, and they were not honed or reblued.

If you look at the Shooting Sportsman from last fall I believe, they had an article addressing concentricity in barrels. The article was mostly about Holland and Holland and their quest for perfection in barrel making. The first few paragraphs asks the question; how to quantify what constitutes a safe barrel when buying vintage guns? The stated industry standard as mentioned in that article is 20 thou, not 25. It is important to clarify that this measurement should be beyond the mid point of the barrel set.

In all the measuring I have done, there has never been an American made double that had barrels with concentric boring. They all are signifcantly thicker on one side of the barrel than the other. The thinnest point is usually found in about an area that would constitute 1/8 of the total circumference of the barrel and in a 8-10" longitudinal line. The rest of the barrels are substantially over the minimums.

Just an FYI

[Big D]

I had an opportunity to spend about 4 hours in the H&H factory last summer. Watching them hone barrels was astounding. An abrasive-covered lead plug was inserted into the barrel, spun at a rather slow speed, and was loosely guided by the bores. As a result, it appeared to me that the bores would not be concentric with the outside. It looked like a process which was unchanged in 150 years. I wonder how the hign volume Berettas and Brownings are done? Betcha it ain't the method I saw, and I'd bet they are concentric

[Bruce Day]

Jay, I have three 20ga Parkers, two fluid, one damascus, and all are in the low 30's. My thinnest is a light 2 frame Bernard 12 with .028/.030 but I know that was Parker honed once. That's interesting you should say that about 20ga's but the ones I've seen were all in the low 30's, like .031.

I did encounter a gun where the chokes had been opened and were not concentric. The patterns were lousy and were only saved by opening them up further, correctly.

[Dean Romig]

I have a twelve bore Damascus GH on a 1-frame with .019" wall thickness in the right barrel and have shot it quite a lot but I'm not going to tell anyone who has similar wall thickness that their barrels are perfectly safe so I posted .025" as a generally-accepted wall thickness.

Wall thickness at the muzzle, which was the question that Dave began this thread with, is in my opinion not much of a concern. Farther back from the muzzle is where we should be concerned. Sure, there are a lot of guns with wall thickness of less than .025" that we shoot all the time but we should keep in mind that a significant number of people who read this forum might get the wrong idea and try shooting an unsafe gun.

[jay shachter]

Hello Bruce, Are you measuring at muzzle's end, or 6-12" back. No doubt a gun with choke remaining can measure 20 thou 10" back in one small section and still be 30 thou at muzzle's end. I need to revise my above statement. I keep a spread sheet on all of the guns I have owned, even the sold ones, and just went back and reviewed the actual data on consigned guns, owned guns, and sold guns, about 120 Parkers on record. I stated "most 16 and 20's are in the 20-25 thou range". Not true, but close. Looks like about 30 percent are, majority between 25-30 thou, and a few over 30 thou. Lots of #1 frame 16's and 12ga. guns are over 30 thou.

In regard to John Dallas' comment on Holland and Holland honing, that process is mentioned in the Shooting Sportsman article that was actually at least a 2 issue series. There is no doubt that Holland and Holland claims to be one of the only gun makers on the planet that gets true concentricity. I do not know how the modern Continental stack up. The honing process John is describing is to eliminate almost imperceptible machining marks left by the process of finishing barrels, not to bring bores to finished dimensions. I no longer keep my magazines. My 15 year old special needs boy loves them and loves to shread them over time. Anyone out there still retaining their issues could clarify this for us. I am going by memory.....and I am officially a senior citizen at 55 years old!!

Bruce, let me know where you are measuring. I have handled a few of your fine Parkers, and they did not seem heavy to me. What do they weigh? To get a true lightweight Parker 20 or 16 they had to save weight somewhere. Why do some 20ga. guns with full length stocks, same length barrels, same size frame weigh 6 1/2lbs. and a visually similar gun weigh just 6lbs. They had to remove weight somewhere, and it involved striking the barrels down to thinner dimensions, among other things. How do they get a 30" barreled gun to be both light and balance on the hinge pin, with no lead or weight added to the butt? They struck the barrels thinner, and maybe chose a stock blank of the correct density. Lots of questions in the vintage gun world. Only speculative answers in many instances.

Interesting topic. The area of greatest pressure spike if you view a ballistic engineer's graphing of pressures is in the first 13" of barrel just forward of the breech. Things lighten up significantly from there and then build again slightly just before the choke constrictions. Thickness at muzzle end is less of a safety issue, more of a physical use issue. If you are 20 thou or so in that "low pressure zone" behind the chokes and at least 15" from the breech, the Brits say you are good to go for modern ammo commensurate with the gun's intended loadings.

[Bill Murphy]

I recently purchased a #1 frame 16 that the seller claimed has .025 wall thickness and .665 bores. The condition of the gun, in pictures, would not indicate that it had been struck harshly. When I receive the gun and measure the wall thickness, I expect to find more than .025, at least I hope so. However, at .025, I will shoot it without concern for safety.

[Bruce Day]

Jay,thanks for the compliment. I measure at mid barrel, not at the thickening created by choke constriction.

Maybe I am just lucky with my 20's. Two particularly on point

1904 CHE 20/26 damascus .031 wall thickness, wt 6 .25lbs

1910 DHE 20/24 Titanic 5lbs14oz. This gun is so light I long thought it had thin barrels, but we measured and they were .030. Short barrels and checkered butt accounts for the light weight.

[Bruce Day]

Bringing this back to the top. Jay and several others were discussing barrel wall thickness back then.

Since then, Jay and I spent a while measuring barrel walls while at a gun show. I can vouch they they would be nominal diameter for the gauge yet we clearly saw some small bores with factory thin barrels. I concluded that small bore guns, the 20's and 16's were best for standard pressures for the gauge, but with the thicker barrel walls in the 12's , you had more of a safety margin for greater barrel pressures.

More reasons to know your barrels.

Drew posted a picture of a burst fluid steel barrel in the other thread. Just going on the visual, those barrels don't look thin to me.

[Richard Flanders]

The 26" VH12 I have with only .017" left at the thinnest spot in the cyl side bbl started out as a F/F gun with .034" in the muzzles. The cyl side is actually now a blunderbuss with a +.004" choke. Imagine my thrill when I discovered that. I don't worry about the safety of shooting it as I only shoot 1oz 3dram loads in it for upland hunting and I've taken a lot of birds with that gun. It's my best shooter ever for me. Still, the choke work makes me ill, read that as "pissed", when I look at it. What an embarrassing lesson that was....

[John Farrell, Charter Member #33]

Here is a set of comments from a Brit gun seller on barrel wall thickness.

Notes on Proof and Barrel Wall Thickness of Shotguns

Here at George Gibbs Ltd we have a policy of selling secondhand shotguns with a minimum of .004" of proof size remaining and a minimum of .025" of barrel wall thickness at 9" from the muzzle (for shotguns of 28 bore to 12 bore inc)

We will sell guns with measurements of less than these figures but will indicate the sizes and offer the gun at a reduced price. The reason for this is we hope that any gun we sell will give years of service for the new owner and with our minimum measurements,we feel we can repair even quite severe damage to barrels eg dents , pitting , without compromising the owners investment in the gun.

Our experience tells us that shotgun barrels with a minimum wall thickness below .025" ( 25 thousands of an inch) are not dangerous to shoot nor are they more likley to fail a proof or reproof test , however the thinner the barrel the easier it is to dent them and the harder it is to repair them , indeed the repair of thin barrels makes the barrels even thinner thereby compounding the problem ! This is why we adopt our policy on wall thickness , in order as practical gunmakers to give you , our customers , good service and peace of mind .