Author Topic: Barrel wall thickness  (Read 896 times)

Offline mikeyfirelock

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Barrel wall thickness
« on: April 02, 2024, 12:56:07 AM »
I am thinking of repurposing a barrel that I’ve had for a long time but never used.  It is a 13/16 octagonal in .45 cal. And I suspect that I cut the slots for the tenons a bit   
“ generously” .   I measure them at 0.100 “ deep ( at 6 in. Ahead of breech face.)
This leaves a barrel thickness at that point that I calculate at 0.175 - 0.180 “ and I have reservations about building a rifle around this one.     Do I have a derringer barrel and 2 dueling pistol barrel at this point ?
Mike Mullins ( aka Mikeyfirelock)
Mike Mullins

Offline Hungry Horse

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Re: Barrel wall thickness
« Reply #1 on: April 02, 2024, 01:27:46 AM »
 I had a friend bring me an old Belgium made trade gun to look at, and see if it might be in good enough shape to shoot. I took it apart and examined all the crucial parts to make sure it was safe. When I got to looking at the barrel   I found that it had a spot on the underside of the barrel that looked like it had been repaired. After cleaning the repair’,  I found that it likely was repaired after its proofing in Belgium. The small crack had been sweat brazed closed and had not created problem for the rest of the guns working life.

 So, on your gun, I would put the lug in the generous dovetail, and braze it in place. And don’t forget to give any new owner a heads up about the repair. I’m sure we won’t have to worry about you overloading it, you’ll be thinking about that lug every time you pull the trigger.

Hungry Horse

Offline mikeyfirelock

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Re: Barrel wall thickness
« Reply #2 on: April 02, 2024, 02:30:45 AM »
Thank you, Hungry Horse.   I was on the fence about it.   I think I might still use it for a pair of pistols…….i can make a very nice pair, and still have enough left over to make miscellaneous parts as needed.   We’ll see “ which way the wind blows” down the road.  Thanks again
mikeyfirelock
Mike Mullins

Offline Manitou

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Re: Barrel wall thickness
« Reply #3 on: April 02, 2024, 02:16:44 PM »
Pistols generally have a faster twist rate than rifle barrels.
You can make pistol barrels from a rifle barrel, but I doubt that you will get as good of accuracy from them if this is important to you.

Offline rich pierce

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Re: Barrel wall thickness
« Reply #4 on: April 02, 2024, 03:14:32 PM »
I am thinking of repurposing a barrel that I’ve had for a long time but never used.  It is a 13/16 octagonal in .45 cal. And I suspect that I cut the slots for the tenons a bit   
“ generously” .   I measure them at 0.100 “ deep ( at 6 in. Ahead of breech face.)
This leaves a barrel thickness at that point that I calculate at 0.175 - 0.180 “ and I have reservations about building a rifle around this one.     Do I have a derringer barrel and 2 dueling pistol barrel at this point ?
Mike Mullins ( aka Mikeyfirelock)

I’m thinking of this. A 7/8” octagon barrel in .50 has .375/2 or .187” wall thickness. And people put dovetails in such barrels. Maybe my math is off or I’m not understanding the situation properly.
Andover, Vermont

Offline Gaeckle

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Re: Barrel wall thickness
« Reply #5 on: April 02, 2024, 09:22:44 PM »
I am thinking of repurposing a barrel that I’ve had for a long time but never used.  It is a 13/16 octagonal in .45 cal. And I suspect that I cut the slots for the tenons a bit   
“ generously” .   I measure them at 0.100 “ deep ( at 6 in. Ahead of breech face.)
This leaves a barrel thickness at that point that I calculate at 0.175 - 0.180 “ and I have reservations about building a rifle around this one.     Do I have a derringer barrel and 2 dueling pistol barrel at this point ?
Mike Mullins ( aka Mikeyfirelock)

I’m thinking of this. A 7/8” octagon barrel in .50 has .375/2 or .187” wall thickness. And people put dovetails in such barrels. Maybe my math is off or I’m not understanding the situation properly.

We often see these 7/8th by 50 barrels show up in our class at the Log Cabin. The students haven't grasped the concept of cutting lugs into these barrels and removing metal. We will instruct them to reduce the thickness of the lug and then install those. A simple demonstration is all it takes. Most of the lugs available are in a one size fits all size are somewhat thick and the students think that the entire thickness needs to be installed into the barrel, which is not the case. Personally I install the first lug about 10 1/2 to 11 inches from the breech

Offline Steeltrap

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Re: Barrel wall thickness
« Reply #6 on: April 02, 2024, 10:28:09 PM »
Just doing the math here, and I seem to be missing something (maybe?)

A 13/16 barrel measures .8125 across the flats. A 45 caliber bore measures .450. That leaves a difference of (.8125-.45)=.3625. Then half of that would be the wall thickness, or .18125.

If you cut a grove .100 deep, then you have left .8125 (81-thousands) remaining.

On the matter of using a rifle barrel for a pistol, since you have the barrel at 45 cal, you could simply have them rebored to .50 cal with a faster twist. That's what I plan on doing for next winters project.

Online Bob Roller

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Re: Barrel wall thickness
« Reply #7 on: April 03, 2024, 12:23:44 AM »
Rifling in any barrel that is .100 deep can be classified as splines as seen in the hub of a standard shift clutch. Many barrels have been made and sold that were made from material that was NEVER intended for the pressures of an abrupt ignition of any kind of powder used to launch a projectile.Antique barrels are a gamble and if one of these blows up there is no recourse.How many modern makers of barrels dedicated to black powder have product liability insurance is not known.I don't know of any black powder barrels from the 1800's that was 13/16 across the flats other than a percussion revolver in 44 caliber.Caveat Emptor applies here.Deep dovetails for sights are another hazard that can be
a threat when enthusiasm is substituted for skill and ability to measure accurately.Making pocket pistols from these this barrel makes sense.
Bob Roller
 
« Last Edit: April 03, 2024, 12:38:30 AM by Bob Roller »

Offline Daryl

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Re: Barrel wall thickness
« Reply #8 on: April 03, 2024, 09:27:46 AM »
One of Bob's points is that typical rifling is .010" to .016" deep, not 1/10" deep.
Daryl

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Offline Manitou

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Re: Barrel wall thickness
« Reply #9 on: April 03, 2024, 02:19:42 PM »
Before retiring, I spent 38 years as a toolmaker/ tool designer/ Mechanical Engineer for an electronics Corporation.
During that time I also belonged to the old, now defunct MLML (or Muzzle Loading Mailing List).
This barrel discussion came up a lot, so I made a drawing of several different barrel cross sections in different widths and their common calibers as a visual reference.
I would like to post it here if the moderators will allow.
Manitou

Offline rich pierce

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Re: Barrel wall thickness
« Reply #10 on: April 03, 2024, 02:50:54 PM »
Before retiring, I spent 38 years as a toolmaker/ tool designer/ Mechanical Engineer for an electronics Corporation.
During that time I also belonged to the old, now defunct MLML (or Muzzle Loading Mailing List).
This barrel discussion came up a lot, so I made a drawing of several different barrel cross sections in different widths and their common calibers as a visual reference.
I would like to post it here if the moderators will allow.
Manitou
Sounds interesting. Maybe start a new post; more might see it.
Andover, Vermont

Offline Kevin Houlihan

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Re: Barrel wall thickness
« Reply #11 on: April 03, 2024, 04:32:20 PM »
Just doing the math here, and I seem to be missing something (maybe?)

A 13/16 barrel measures .8125 across the flats. A 45 caliber bore measures .450. That leaves a difference of (.8125-.45)=.3625. Then half of that would be the wall thickness, or .18125.

If you cut a grove .100 deep, then you have left .8125 (81-thousands) remaining.

On the matter of using a rifle barrel for a pistol, since you have the barrel at 45 cal, you could simply have them rebored to .50 cal with a faster twist. That's what I plan on doing for next winters project.


 A .100” dovetail for a barrel lug is excessive. I would only go .050” at the most - or even less.

Offline DGB

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Re: Barrel wall thickness
« Reply #12 on: April 03, 2024, 05:28:46 PM »
Good morning folks,
I have been making both barrel lug and sight dovetails about .040 deep. Spelled out that is forty thousands deep. I say that because I am seeing deminsions being given here with the decimal point in the wrong place. That can lead to BAD consequences!
Regards,
DGB

Offline Steeltrap

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Re: Barrel wall thickness
« Reply #13 on: April 03, 2024, 06:25:23 PM »
Good catch. The remaining wall thickness of a 45 cal is .18125. Subtracting.10 from that leaves .08125….just over 80-thousands.

Always check somebody else’s math. Remember, measure twice, or more, cut once.

Offline bluenoser

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Re: Barrel wall thickness
« Reply #14 on: April 03, 2024, 06:39:48 PM »
A sanity check is always a good move that has saved my bacon more times than I care to admit.
That said - I really don't think we need to calculate our tolerances to five one-hundredths of one thousandth of an inch.  I have trouble enough holding to the nearest thou.
Just sayin ::)

Offline Mike Brooks

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Re: Barrel wall thickness
« Reply #15 on: April 03, 2024, 08:28:52 PM »
The first 10-12 inches at the breech are important. The rest of the length, not so much. All the pressure is gone.
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Say, any of you boys smithies? Or, if not smithies per se, were you otherwise trained in the metallurgic arts before straitened circumstances forced you into a life of aimless wanderin'?