Minimum Barrel wall thickness

[shortbarrel]

What would be the minimum wall thickness at the waist of a 39 inch 64 cal. barrel. Waist is 28 inches from the breach. Seen all kind of figures on this.

[Bob Roller]

What would be the minimum wall thickness at the waist of a 39 inch 64 cal. barrel. Waist is 28 inches from the breach. Seen all kind of figures on this.

I would think that dimension would be dependent on the barrel material.A .64 is .015 over a 5/8"bore.
In 4150 CERTIFIED for gun barrels steel I would want at least 3/16 wall thickness at the waist.In other
types I don't know or want one.

Bob Roller

[jerrywh]

 What Bob says is true. Another factor to consider is the fact that the bigger the bore the less the combustion chamber pressure is and the pressure rapidly decreases as the bullet  travels down the bore. By the time the bullet is 28" down the bore the pressure almost ceases to become a factor as long as the barrel is unobstructed. The other factor to consider is accuracy. Super thin rifle barrels seem to have a tendency to be less accurate. I personally would not like a barrel that had a thickness of less that .100" at the waist for those reasons.
Shotgun or fowlers are a different story and wall thicknesses can be a lot less. Don't forget the type of metal factor.

[SuperCracker]

Jerry, Bob. 

Are there any publications you could recommend that deal with the math involved and outline a more scientific approach to designing and making a barrel that would be appropriate for our applications?   Short of a complete engineering course. lol

[Acer Saccharum]

Look at some original fowler barrels. some have a 1 3/8 breech, rapidly tapering down to a wafer thin muzzle.

[shortbarrel]

We proofed the barrel mentioned above yesterday at the range.  Three shots with 100 grains of 3F powder and all went well. Wall thickness at the waist was  .070. Miked the waist after shot and it stayed the same. Made a little miss calculation when I made the  barrel,  the wall thickness should have been .080 at the waist. Barrel is made from 12L14 round bar stock. BTW this a fowler barrel........Thanks for the reaplys everyboby.

[Dphariss]

We proofed the barrel mentioned above yesterday at the range.  Three shots with 100 grains of 3F powder and all went well. Wall thickness at the waist was  .070. Miked the waist after shot and it stayed the same. Made a little miss calculation when I made the  barrel,  the wall thickness should have been .080 at the waist. Barrel is made from 12L14 round bar stock. BTW this a fowler barrel........Thanks for the reaplys everyboby.

100 grains is FAR too little for a .64 caliber barrel its little more than a service load. The British proof tables in W.W. Greeners "The Gun and its Development" 1896; show first and second class guns using a 352 gr bullet and 342 grains of powder. Third class guns at 273 grains. This would have been a proof powder that was generally faster than the typical service powder.

Dan

[jerrywh]

 You never told us how thick the breech wall was. I would want a wall thickness of no less than .200 for a fowler at the breech. If you have a good piece of 12l14 I doubt very much if you could cause it to fail with a 300gr. load of FFG and two patched round balls. The book mentioned by Dan has a lot of super good info in it.
  I have a barrel that is a .50 smoothbore. It has a wall thickness of .165 at the breech and tapers to a wall thickness of .032 at  the muzzle and is only 10" long. The steel is 1137 barrel steel from long hammock barrel co. I fired it with 150 grs of fffg and two patched round balls three times. It shows no sign of deformation. Every barrel is different. It does no good whatsoever unless you give it a good strong proof. 100 grs is a toy load for that gun barrel.

[Daryl]

Just as information, many of the Bess' made in India (shipped without a vent) have a wall thickness at the breech of 1/10" each side ahead of the plug , which may have 3 to 5 threads bearing.  That is why I sent the one I bought, back.
Scared the guanno out of me.

[shortbarrel]

Hmmm! I just wonder how many american welded wrought iron barrels could have survived the British proof standards   Barrel is 1.125 at breech

[jerrywh]

 I don't think you will have any trouble with that barrel.  Go proof it. 300 grs ffg. or more about three times. Measure the barrel at 6" intervals  after each shot. Mark the spots off where you measure it. Then if your still scared send it to me. I will pay you $25.00 for it plus shipping. I will make pistol barrels out of it.

[T*O*F]

I just wonder how many american welded wrought iron barrels could have survived the British proof standards

Just because it wasn't required by law doesn't mean that American gunmakers didn't prove their barrels before using them.  They wouldn't sell many guns if they blew up after a customer paid good dollars for them.

[Dphariss]

Hmmm! I just wonder how many american welded wrought iron barrels could have survived the British proof standards   Barrel is 1.125 at breech

The Springfield Rifle Musket was a thin wall iron barrel. From my reading it was proofed with 200 gr of musket powder and a 500 gr minie spaced 2" off the powder (the Army knew the bullets tended to move in the bore it seems). These were welded from a flat skelp into a tube and then rolled to length/contour. I would point out that the English made a LOT of welded barrels. And true a lot of cheap "foreign" barrels would not pass proof.  I would also point out that this was not a welded barrel under discussion. Its a steel many seem to think is stronger than wrought iron. However, wrought iron properly welded will stand about any pressure that BP will make in a gun barrel. BP is hard pressed to make 30000 in a gun barrel. Even in brass suppository guns. Wrought iron is stronger that this. But people like to believe the myth that cold rolled questionable alloy steels are somehow better. In reality this is not the case and in fact an iron barrel of "best iron" as the Rifle Musket barrels were, is actually a good barrel for our purposes. If it passes proof its probably good for a very long service life. I often wonder if the increase in barrel wall thickness in the 1830-50 period was not the result of steel barrels of unknown alloy being used.
If we do some research into digs around native villages and forts we find the remains of trade gun barrels this incredible levels of inclusions that did not fail. I have no idea if they were proved, but if they were made in Europe its likely they were

Dan